Bridge_design_jkr_specification.pdf

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Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification

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Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification

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CONTENTS CHAPTER 1 - INTRODUCTION

Bridge Design For JKR Specification concrete beams have been the first choice since then, because they are economical and durable. For longer spans, prestressed concrete box girders have been used, the first of which was constructed in 1974.

CHAPTER 2 - BRIDGES - AN OVERVIEW CHAPTER 3 - BRIDGE DESIGN STANDARD AND CODE OF PRACTICE CHAPTER 4 - DESIGN PRINCIPLE AND APPROACH CHAPTER 5 - BRIDGE LOADING PART I CHAPTER 6 - BRIDGE LOADING PART II CHAPTER 7 - DESIGN OF SUBSTRUCTURE WORKED EXAMPLE

Other types of structural forms are less common. Most of the steel truss bridges can be found in East Malaysia (Sabah and Sarawak). Some trusses are mainly in the form of Bailey bridges. However they are usually used as temporary crossings. Bridge Type

Number Percentage

Pipe Culvert Box Culvert Precast Concrete Beam and Deck Slab Bridges Reinforced Concrete Beams Bridges Buckle Plate Bridges Reinforced Concrete Slab Bridges Concrete Arch Bridges Steel Beam Concrete Deck Bridges Steel Trough

3330 1348

50.1% 20.3%

665

10.0%

557 233

8.4% 3.5%

219 159

3.3% 2.4%

126 12

1.9% 0.2%

Total

6649

CHAPTER 1 - INTRODUCTION Modern road bridge construction is relatively new in Malaysia, having been started in the early twentieth century. Most of the bridges were constructed using established materials and technology at the time of construction. Early bridges were made up of simple structures. The earliest bridges were constructed using steel beams and curved steel plates. This form of construction, which was introduced in the early 1920s, came to be known as buckle plate bridges. This form was popular until the late 1950s. Earliest reinforced concrete bridges were constructed in the early 1930s. Standard reinforced concrete beam bridges however only became common in the 1960s with the introduction of precast reinforced concrete beams. Prestressed concrete was first used in bridges in Malaysia in the early 1950s. For most short to medium span bridges, standard prestressed Cawangan Jalan, Ibu Pejabat JKR, K.L

Table 1.1 - Bridges on Federal Road in Peninsular Malaysia. Source: JKR - BMS

CHAPTER 2 - BRIDGES - AN OVERVIEW

2.1 Introduction All bridges can be considered as made up of various components. Many times a bridge that is considered to be a non-concrete bridge will have numerous components that are made up of reinforced or prestressed concrete. For instance, a typical steel beam or girder bridge, which would be classified on the standard inventory and appraisal form as a steel bridge, would most likely have reinforced concrete abutments and piers as well as a reinforced Page 3

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Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification

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Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification

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concrete deck. These components, although on a non-concrete bridge, would be evaluated as if they were part of a reinforced or prestressed concrete bridge.

2.2

Classification of the Bridges

The bridge designers and inspectors must be familiar with the various types of bridges and its components that may be constructed of concrete, steel and other materials. Bridges are constructed for various purposes to support roads and highways at strategic points along their routes. Bridge structures are required to cross over rivers and valleys, or for grade separation with other roads and railways. Bridge structures are also required to be built over roads and bridges just for pedestrian crossings. Bridges are generally classified and separately called by purpose as follows:

Bridge Design For JKR Specification requires that the bridge designer/inspector include several modifying terms, such as if the primary load-carrying member is concrete, the bridge is classified as a concrete bridge, if the member is steel, the bridge is classified as a steel bridge. This classification applies even though other components, such as the deck or piers, are a different material. The type of span design also enters into the description of the bridge. Each bridge is described in according to type of span designed such as simple spans, cantilever - suspended spans, or continuous spans. Description of type of bridges. 1. The primary load-carrying member or members. Example: T-beams, 1-beams, box girder, slab, arch, trusses, frame.

(1) Road or Highway Bridges Any bridge on roads and highways.

2. Material of primary load-carrying member Example: Concrete, steel.

(ii) Railway Bridges. Any bridge on railways.

3. Type of span designed. Example: Simple span, cantilever-suspended spans, continuous spans.

(iii) Flyover or Overpass Bridges. Bridges for grade-separation with other roads, highways or railways at intersection. (iv) Viaducts. Bridges to support elevated roads, highways, or railways, which are built mainly at where ground space is limited in urban area or embankment is difficult for ground is soft. (v) Overhead Footbridges. Bridges for pedestrian crossing.

2.3

Types of Bridges.

A bridge is classified by the primary load-carrying member or members. For example, for girder-deck systems, the bridge esigner/ inspector classifies the bridge according to the type of girder used (T-beams, I-beams, and so on). An accurate description of a bridge Cawangan Jalan, Ibu Pejabat JKR, K.L

2.4

Types of Concrete Bridges.

2.4.1 Slab Bridges A concrete slab bridge is nothing more than a wide shallow beam in which the beam itself acts as the deck. A concrete slab bridge is usually continuous, although some simple span slabs exist. Slabs can be made of either reinforced concrete or prestressed concrete. Precast units are sometimes used to form a slab bridge. Several types of precast concrete units are used by various highway agencies in slab bridge construction. These precast units include channel slab, solid slab, voided slab, and the pan slab. These special precast units may be constructed of either reinforced concrete or prestressed concrete.

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2.4.2 Girder or Beam Bridges. A girder or beam bridge consists of a deck supported directly by longitudinal girders or beams. Concrete girder or beam-type bridges may be either reinforced concrete or prestressed concrete and usually precast. Most concrete-beam-type bridges are also composite; that is, the beam and deck have a load-carrying connection between the beam and deck. This composite section allows the beam and deck to act together to carry the load. The T-beam, Mbeam, Y-beam, Inverted T-beam, U-beam and the Ibeam are the common beam or girder-type concrete bridges. The T-beam is generally a cast-in-place monolithic deck-and-beam system. The T-beam is named such because of the "tee" shape used in a typical analysis of the section. 2.4.3 Box Girders Concrete box girders have become quite popular in recent years. As the name implies, the girders are constructed with a cross section that is rectangular or box-shaped such that the roof and floor act as flanges and the walls act as webs. The bridge may be a large box, or a multitude of smaller boxes. These structures may be simple span or continuous and either prestressed or reinforced concrete. The box units may be castin-place or precast, depending on the location or experience of the highway agency involved. Segmental box girders are frequently used for long span bridges. These units are very large box girder segments usually constructed by a cantilever method. The concrete segmental box girders are also used in cable-stayed bridges.

Bridge Design For JKR Specification individual openings or boxes of less than 20ft, but grouped together, they meet the definition of a bridge and must be regarded as bridge. Concrete box culvert is usually analysed as a continuous concrete frame and is frequently used over small or intermittent waterways. 2.4.5 Truss A rare type of bridge is the reinforced concrete truss. A truss bridge is one of in which the main supporting members are made up of a series of triangles the sides of which act in tension or compression. 2.4.6 Frame. A rigid frame reinforced concrete bridge is one in which the piers or abutments are casted monolithically with the main supporting member, either girders or slab, so that the abutment can assist in carrying the main supporting member loads. These rigid frame bridges can be single span or multispan as in a concrete box culvert. The bridge presents a pleasing aesthetic shape primarily because of the relatively long span with a shallow depth. 2.4.7 Arch. A concrete arch is the natural extension from Roman stone arch. The true arch carries load by direct compression. The concrete arch bridge is generally of three types: - the open or spandrel arch - the filled arch - the through tied arch

2.4.4 Concrete Box Culverts A concrete box culvert consists of a box-like concrete frame, generally normal to the roadway, which has a waterway or roadway passing through the culvert underneath the roadway. The National Bridge Inspection Standards (NBIS) USA defines a culvert as a bridge if the distance from backwall to backwall equals or exceeds 20ft. Concrete box girder may have Cawangan Jalan, Ibu Pejabat JKR, K.L

The spandrel arch consists of the deck system supported by columns or bents, which rest on the arch proper. The filled arch has fill material contained by walls resting on the arch. The third and older type, which resembles a truss, is the through ties arch. The main supPage 7

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porting member is the arch which hangers supporting a floor system and deck.

Bridge Design For JKR Specification

In all cases, the arch proper can be though of as a long curved column.

Several precast T-beam shapes are used by various highway agencies. This include the bulb tee, the double tee, the quad tee, the rib tee, and decked bulb tee.

2.5 Superstructure

(i) M-beam

2.5.1 Concrete Decks. The deck is the load-carrying part of the superstructure that has direct contact with the wheel loads on a typical highway bridge. The most common construction material for decks is reinforced concrete. These decks are usually cast in place. Some concrete decks are precast, prestressed units if the designer wanted to take advantage of the compressive strength of the concrete or minimise cracking of the deck. The precast units are becoming popular as replacement decks where maintaining of traffic during replacement is a concern. Concrete decks on girder bridges normally have the primary reinforcement in the transverse direction or perpendicular to the girder.

The pretensioned prestressed M-beam was developed in the late 1960s as a beam which could conveniently be used to form a voided slab deck. It was modelled on the inverted Tbeam but was made a wider metre width module. In the 1960s the I-beam deck was used with the in-situ diaphragms in the span, the moulds in fact providing holes for transverse steel at 3.050m centres. The properties and normal construction of inverted T-beam, I and box section bridges, at that time. In the late 1960s the better structural efficiency of a voided slab, rather than that of an I-beam and slab, layout was appreciated, as was the capacity of a voided slab to do without the need for inspan diaphragms. A joint Ministry of Transport, Cement & Concrete Association and industry based development programme in U.K resulted in the derivation of the M-beam shape

2.5.2 Beams/Girders A girder or beam bridge consists of a deck supported directly by longitudinal girders or beams. Concrete girder or beam-type bridges may be either reinforced concrete or prestressed concrete and usually precast. Most concrete-beam-type bridges are also composite,; that is, the beam and deck have a load-carrying connection between the beam and deck. This composite section allows the beam and deck to act together to carry the load. The Tbeam, M-beam, Y-beam, Inverted T-beam, Ubeam and the Ibeam are the common beam or girder-type concrete bridges. The T-beam is generally a cast-in-place monolithic deck-andbeam system. The T-beam is named such because of the "tee" shape used in a typical analysis of the section. Cawangan Jalan, Ibu Pejabat JKR, K.L

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which was publicised in 1971. Parameter study carried out in U.K pointed some weakness of M-beams as follows. (i)M-beams were placed closely during construction. The current need for inspection of bridge structures, spaces between bottom flanges of beams are needed for access and inspection.

Bridge Design For JKR Specification the construction. This is by far the most application., With the new requirement for inspection in mind and a further desire for economy, some designers placed M-beams with gaps of up to 500mm and more between them. This had the penalty of the need for a deeper beam and possibly a deeper slab but does not have the advantage that all the superstructure may be inspected.

(ii) The lower flange of the beam should be deeper than in a M-beam to allow for the increased prestress used in recent designs and also to allow higher covers for links without impinging on manufacturing tolerances and without requiring links to be bent through nonstandard radii. (iii) The lower flange should have a more steeply sloping top surface than on Mbeams to keep it clean of debris and to allow it to be cast without air bubbles and water gain under the shutter forming the upper surface of the bottom flange. (iv) The beam should be ideally not have a discrete top flange in order to eliminate the need for such a top flange to be provided with a set of small portion links, as increasingly the case with M-beams. (v) The beam should have a top flange that would allow it to have an end cross diaphragm which is not the full depth of the deck. This configuration is common in standard U-beam bridges and allows access for jacking for bearing maintenance and replacement.

(ii) Y-beam M-beam decks were originally envisaged as having a solid bottom flange with infill concrete and top flange cast on lost formwork. An end diaphragm was used in all cases. This method of construction was found to be expensive and, with the penalty of going to an extra beam depth, it was possible to eliminate the lower flange completely, greatly simplifying Cawangan Jalan, Ibu Pejabat JKR, K.L

After a series of reserches had been carried out, Y-beam was introduced in January 1991. The main points and advantages of M-beam are as follows: Š Used on beams and deck slab of 14 to 32 metres long Š Better durability than existing bridge beams due to optimum shape for spaced beam and slab construction Š All of deck, including between beams, readily inspectable o Cost less than M-beams Š Absence of discrete top flange allows easier diaphragm and continuity detailing Š Decks may be shallower than M-beam decks

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Bridge Design For JKR Specification

(iii) T-beam (v) I-beam T-beams were introduced in the early 1990s. The concept of a T-section arose to replace Ibeams. Their shapes are nearly the same except that T-beams are having wider and thin top flanges. The main purpose of this top flange is to form the permanent formwork for deck slab construction. Because of this, the construction time could be shortened and they had better aesthetic appearance as compared to Ibeams. Due to this advantage features, they became popular and increasingly replaced I-beams. Now T-beams are become the first choice beams for bridges having span ranging from 25 meter to 45 meter.

The most common concrete I-beam shape is the AASHTO shape used by most state highway agencies. These 1-beams are normally precast and prestressed. Several highway agencies have developed variations of the AASHTO shapes to accommodate their particular needs. Older prestressed girder bridges are generally simple spans, where as many of the newer bridges are simple span for dead load and continuous for live load. These bridges utilise castin-place continuous decks constructed on precast prestressed girders.

(vi)

(iv) U-beam The development of U-beams was started in 1971 where the cross-section of a deck incorporating U-section beams. The main advantage of U-beams is, in conjunction with an insitu deck slab the necessary torsional stiffness is provided for the distribution of live loads. Cawangan Jalan, Ibu Pejabat JKR, K.L

JKR Standard Beams

The Bridge Rehabilitation and Maintenance Study in 1992 highlighted the various problems of the bridges in this country. Some of the problems came from lack of uniformity in both design and construction. This study also recommended the standardisation of bridge design, to improve the design, construction and maintenance of bridges in the country. In the study, the pre-cast pre-stressed structural members were developed after taking into account the technical and production capability Page 10

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Bridge Design For JKR Specification

of the local manufacturers. Simple sectional beam shape with straight edges were adopted in the study to ensure high quality finished products. In selecting the pre-cast beam, the study team has also tried to reduce initial investment cost of new bedding by the manufacturers. Following are the summary of the slab and precast prestressed beams recommended by the study to be adopted by JKR.

2.6

Other Elements

2.6.1 Expansion Joint Introduction The expansion joint is an integral part of any bridge structure and as such must be considered at an early stage in design. If the expansion joint is carefully designed and detailed, properly installed by specialist operators and given reasonable maintenance in service, it should be trouble free for many years. It is important to appreciate that the expansion joint is in the most vulnerable position on any bridge, situated at surface level where it is subjected to the unabsorbed impact and vibration of the traffic and exposed not only to dust, silt, grit and water but also to the effects of ultraviolet rays, ozone attack and chemicals such as salt solutions, cement alkalis and petroleum derivatives.

Expansion Joints Requirements In view of the aggressive situations above, the

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Bridge Design For JKR Specification

following requirements must be met in selecting an expansion joint. It must

2.6.2 Parapet

(i)accommodate all movements of structure and withstand all loadings;

Introduction

(ii) not impart stress to the structure unless the structure has been designed accordingly; (iii) have good riding characteristics;

The main objectives of the forms of parapet are (i)To provide specified levels of containment to limit penetration by errant vehicles.

(vi) be silent and vibration free in operation;

(ii) To protect highway users and others in the vicinity by redirecting errant vehicles with minimum deceleration forces on to a path as close as possible to the line of the parapet and to reduce the risk to the vehicle of overtopping the parapet and of overturning.

(vii)give reliable operation throughout the expected temperature range;

General Design

(iv) not present a skid hazard; (v) not present a danger to traffic such as cyclists, animals, etc;

(viii) be sealed against water and foreign matter or make provision for their disposal;

(i)Level of Containment Normal level of containment

(ix) resist corrosion and withstand attack from grit, chemicals, etc; (x) facilitate easy inspection, maintenance and repair. Today there is a large variety of proprietary expansion joints on the market and the problem facing the bridge engineer is now so often that of selecting the most suitable joint to give good performance and a trouble free life for at least as long as that of the surfacing. Types of Expansion Joints Expansion joints are classified by the magnitude of movements of the structure in longitudinal mode. (i)Joint for small movements (Below 10mm) (ii) Joints for medium movements (10 - 25mm)

Vehicle Mass Height of centre of gravity Angle of impact Speed

: Saloon car : 1500 kg : 600mm : 20° : 113 km/h (70m/h)

High level of containment Vehicle

: 4 axle rigid tanker or equivalent Mass : 30,000 kg Height of centre of gravity : 1800mm Angle of impact : 20° Speed :64 km/h (40 m/h) (ii) Vehicle Impact Loading The parapet shall be designed to resist loading appropriate to the designated level of containment usinp- the equivalent static nominal loadings from Table 2.1.

(iii) Joints for large movements (Over 25mm)

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Bridge Design For JKR Specification

FOR INTERNAL USE ONLY Parapet Containment Level Nominal * without shear transfer provision between panels High • with shear transfer provision between panels • without shear transfer provision between panels

Panel Nominal Bending Moment

Panel Nominal Shear

50 kN over lm

80L kN/panel

(180 + 40L) kN/panel

(90 + 50H) L

(210 + 40L) kN/panel

(110 + 50H) L

Panel Joint Nominal Shear Transfer

110 kN

Table 2.1 - Equivalent static nominal loads for insitu and precast concrete parapets applicable to panel lengths (L) 1.5m to 3.5m

(iii) Parapet Height The minimum height of concrete parapets shall be measured from the datum to the top of the front face and it shall be for a particular application as noted in Table 2.2. Parapet Height 1.00 m 1.25 m 1.50.m

Application • for vehicle and vehicle pedestrian parapets • for bridges carrying motorways over railways, or situations where pedestrians are excluded _ • for all other bridges over railways • for high containment applications • for protection of animals Table 2.2 - Height of Parapets

If additional height is required only for the protection of animals, this may be provided by the addition of a metal rail mounted on posts anchored into the top of the concrete parapet. The rail, posts and anchorages shall be designed to resist a horizontal ultimate loadings of 1.4 kN/m applied to the rail.

2.6.3 Bearings

Introduction

The load and movement capacities of the bearing for any particular structure should be compatible with the assumptions made in the overall design of that structure. Where practicable and whenever the expected design life of the bearing is significantly less than of the structure, provision should be made for the removal and replacement of the whole or parts of the bearings. Facilities for correcting the effects of any differential settlement and tilt should be provided unless the structure has been designed to accommodate such effects. Adequate space should be provided around bearings to facilitate their inspection and maintenance. Consideration should be given in the design of the structure to the means of access to the bearings. Bearings should be detailed to exclude crevices and the like, which allow moisture and dirt to be trapped. Where restraints are required to restrict the translational movement of a structure, either totally, partially or in a selected direction, they may be provided as part of or separate from the bearings and normally take the form of dowels, keys or side restraints. In each case the restraints should allow freedom of movement in the desired direction(s).

The function of bearings is to provide a connection to control the interaction of loading and movements between parts of a structure, usually between superstructure and substructure.

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Bridge Design For JKR Specification

2.7 Substructures 2.8

Foundation - Piles

2.7.1 Abutment 2.8.1 Introduction Abutments are the part of the substructure that form the terminal ends of the bridge and support the end spans. Typical types of abutments are full heights, stub or semistub. The abutment is normally composed of footing (pile cap), a breast wall (ballast wall), a bridge seat, wing walls, curtain walls and sometimes approach slab seats on cobel. The most common construction material for abutments is reinforced concrete. Some special cases call for precast units or prestressed units, but the great majority are cast-in-place reinforced concrete. Because abutments are supports for end spans of bridges, they must also retain the soil on the approaches.

2.7.2 Piers Concrete piers are the substructure element between the abutments and are usually made up of capping beams, footings, columns and caps. The footings may be spread, pile or drilled shafts. Each of these components of a pier is frequently constructed of reinforced concrete with precast or prestressed units used occasionally. Another common name for a small pier consisting of a cap or two or more columns or piles is a bent.

Cawangan Jalan, Ibu Pejabat JKR, K.L

Piles are relatively long and slender members used to transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. They are also used in normal ground condition to resist heavy uplift forces or in a poor soil conditions to resist horizontal loads. Piles are convenient method of foundation construction for works over water such as jetties and bridge piers. The load transfer may be by friction, end bearing or combination of both. If the bearing stratum for foundation piles is a hard and relatively impenetrable material such as rock or a very dense sand and gravel, the piles derive most of their carrying capacity from the resistance of the stratum at the toe of the piles. In these conditions they are called end bearing or point bearing piles (Figure 2.8). On the other hand, if the piles do not reach an impenetrable stratum but are driven for some distance into a penetrable soil, their carrying capacity is derived partly from end bearing and partly from the skin friction between the embedded surface of the pile and the surrounding soil. Piles which obtain the greater part of their carrying capacity by skin friction or adhesion are called friction piles (Figure 2.9).

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Bridge Design For JKR Specification

2.8.2 Common Type of Piles Used in Malaysia

steel H-pile is about 300 to 1800kN depending on size.

(1)Precast Reinforced Concrete Piles

(4)Cylindrical Steel Piles (Driven castin-situ Displacement Pile).

Used to be the common used pile in bridge project before the introduction of prestressed spun piles. The pile is designed as compression members and longitudinal steel is provided to withstand bending and tensile stress during handling and driving. The common sizes of reinforced square concrete piles used varies from 250mm to 400mm square section. The usual design load for this type are in the range of 300 to 600 kN. (2)Prestressed Spun Piles This is the most commonly used type pile in bridge project in Malaysia currently. Prestressed spun piles are produced by process of spinning. The concrete used in producing the piles are high concrete strength, e.g. Grade 56, 60 or more. Their principal advantage over ordinary reinforced concrete piles is the higher strength to weight ratio, enabling long slender units to be lifted and driven. The second main advantage is the effect of prestressing in closing up cracks during handling and driving. This effect, combined with the high quality concrete necessary for economic employment of prestressing, gives the prestressed concrete pile increased durability. Sizes varies from 250mm diameter to 800mm diameter. (3)Steel H-Piles Steel piles have the advantage of being robust, light to handle and capable of being driven hard to deep penetration to reach a bearing stratum. They can carry high compressive loads when they are seated in a hard stratum. They can be designed as small displacement piles, which is advantageous in situations when ground heave and lateral displacement must be avoided. They can be readily cut down and extended where the level of the bearing stratum varies. H-section piles are the common steel piles used in this country. The design load for Cawangan Jalan, Ibu Pejabat JKR, K.L

Driven cast-in-place piles are installed by drilling to the desired penetration a steel tube with its end closed. A reinforcing cage is next placed in the tube which is then filled with concrete. The tube is then withdrawn while placing the concrete. This system of pilling is usually patented basing on using different types of shoes of driving technique or casing withdrawal procedure. The system used in this country is patented Franki pile. The design load per pile is in the range of 650 to 1500 kN. Driven and cast-in-situ piles have the principal advantage of being readily adjustable in length to suit the desired depth of penetration. The design load per steel pipe pile is in the region of 200 to 3000 kN. (5)Bored Piles Bored cast-in-place piles are installed by first removing the soil by a drilling process, and then constructing the pile by placing concrete in the drilled hole. The simplest form of construction consists of drilling an unlined hole and filling it with concrete. In water-bearing soils and soft clay, casing is needed to support the sides of the borehole. The casing is withdrawn after placing concrete. In stiff to hard clays and weak rock, an enlarged base can be formed to increase the end bearing resistance. Design load for bored cast-in-situ pile varies from 400 to 6500 kN. (6) Micropiles Micropiles are classified as small diameter (less than 200mm) bored cast-in-situ piles. The special feature of micropile is its strength, resulting from placing of steel and its seating in a hole of sufficient diameter which may be bored in whatever direction is best suited to the requirements of the projects. The equipments used in the installation of micropiles are much Page 15

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smaller than those used in bored piles and so it is very convenient to move and install these equipments. In areas where the ground consist of hard weathered rock they require special diamond-tipped drills and for large diameter boreholes the process of drilling will be quite difficult. Moreover only few contractors can supply these drills. Whereas for micropiles the drilling process can be easily done due to the small diameter. The micropiles are good foundation in fractured rocks where the cracks/fractures can be grouted at the same time of grouting the micropiles. For existing structures where the foundation is found to fail, these micropiles can be used because they do not require large equipments or space to work on and so the other parts of the structure will not effected. The working loads of micropiles as specified by the soils lab are between 400 kN to 800 kN but some contractors claim that they can reach up to 1500 kN for 250mm diameter.

2.9

Authorities Requirements

2.9.1 Waterway Crossing (Jabatan Pengairan dan Saliran)

Bridge Design For JKR Specification

(3) Minimum span length (i) Span length has a direct relation to the possibility of clogging the bridge opening with floating logs or debris. (ii) Pier location close to bank (iii) Impediment ratio of pier width to water way

(4) Abutment Design (i) Retaining Wall-type (or Inverted T-type) Abutment (ii) Embedding depth of pie cap . Footing shall be embedded into riverbed. Where the scouring risk is high, it shall be deepened below the anticipated scour depth. (iii) Parallel to flow Abutments shall be laid in parallel to flow of water.

(5) Pier Design (i) Oval or round shape for pier column (ii) Embedding depth of pile cap Footing shall be embedded into riverbed deeper than the anticipated scour depth.

General Requirement (6) Bank Protection (1) Location and Direction of Crossing (i) Cross river at its straight reach (ii) Cross river in perpendicular to its flow

(2) Waterway Width and Freeboard (i) Lay abutments outside waterway (ii) Minimum freeboard on highest water level (HWL) The freeboard between HWL and the soffit of bridge shall not be less than 1.0 meter.

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Bank protection is required to protect the slope of bank from the erosion which may be caused by the turbulence water flow induced by the construction of piers. (i)Covering Area (ii) Embedding Depth (iii) Foot Protection The toe of bank protection shall be protected against scouring with gabion packs or stones.

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Figure 2.10 shows a diagram issued by Jabatan Pengaliran dan Saliran Negeri Selangor in the pamphlet - Prosedur Memproses Pembinaan Jambatn / Paip Menyeberangi Sungai.

Hydrological Calculation - DID Hydrological Procedures Few methods have been established by the Jabatan Pengaliran and Saliran, Malaysia , to.determine hydrological requirements namely; 1. Rational Method (HP No.5) 2. Unit Hydrograph Method (HP No. 11) 3. Regional Flood Frequency Method (HP No.4) 4. Urban Drainage Design Standards and Procedures for Peninsular Malaysia

2.9.2 Roadway Crossing (State JKR, Local Authorities, Bandaraya, etc.) (1)Information of Crossing Road The following information of the crossing road is required for bridge planning Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification

(i)About Existing Road Š Class and grade Š Cross sectional profile Š Right of way Š Clearance limit Š Longitudinal profile (ii) About Future Plan Š Designated, or not designated to roads of city planning Š Sidewalk plan, or not Š Overlay and widening plan, or not Š Cycle track plan, or not (iii) About Public Utilities (2)Consultation Items The following items are to be consulted with the competent authority of the crossing road: (i)Bridge length and span (ii) Location of abutments and piers (iii) Embedding depth of foundations (iv) Under bridge clearance (v) Diversion road Page 17

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(vi) Construction method (includes protection of existing road and traffic) (3)Vertical Clearance Limit A clearance height of 5.3m above the existing road surface under the soffit of the planned bridge beam is recommended. (4)Location of Abutments and Piers (i) General Abutments and piers are prohibited inside a roadway. It is favourable for the traffic of the crossing road to have sufficient lateral margins between roadway and abutment, and not to have a pier on median strip. However, the following cases are technically and economically very difficult to avoid a pier on median strip: i. Crossing road is very wide having six lanes or more. ii. Bridge is skewed to crossing road with over about 50 degrees even if it has only four lanes or less. iii. Crossing road is separated into up and down lanes. iv.Frontage road and/or waterway run in parallel to crossing road. When a pier is designed on median strip, it is required to consider collision load of vehicles for the design of pier. (ii) Lateral Clearance (iii) Special Lateral Clearance for Expressway

2.9.3 Railway Crossing (KTMB) (1) General Requirements Information of Crossing Railway Similar to road crossing, the following information of the crossing is required beforehand:

Bridge Design For JKR Specification

Š Class and grade Š Rail gauge and cross sectional profile o Right of way Š Clearance limit Š Electrified or not ii. About future plan Š Electrification plan, or not Š Double tracking plan, or not Š Elevating plan, or not (2) Consultation Items The following items are to be consulted with the competent authority of crossing railway: (i) Bridge structural type (ii) Bridge length and span (iii) Embedding depth of foundation (iv) Location of abutments and piers (v) Under bridge clearance (vi) Construction method (includes relocation and protection of existing railway facilities) (vii)Consignment construction, or delegation of supervisors (viii)Installation of guard fence (3) Clearance Limit The clearance limit of railway is different depending on the type and kind of railways. The railway of Malaysia has been developed based on the British gauge and is now in progress of electrification. Figure 2.11 shows the clearance of Keretapi Tanah Melayu Berhad both for the electrified and not electrified. However, in recent years new commuter railway system is going to be constructed in urban area. To cross with such new system, clearance limit should be confined by individual consultation.

i. About existing railway: Cawangan Jalan, Ibu Pejabat JKR, K.L

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2.10 JKR Current Practice

2.10.2 Discouraging The Usage of Close Spaced Beams

2.10.1 Introduction

During bridge inspection, bridge engineers are facing problem in inspecting deck slab of the closed space beams. Based on this difficulty, the department had come up with a policy to discourage and finally eliminating the usage of closely spaced beams.

Based on The Annual Mandatory Bridge Inspection (AMBI) for 1995. Irrespective of the type of observed defects, one of the agents to the initiation and propagation of defects was the presence of water. In view of the observed defects, some new design procedures were adopted whether the design would be carried out in-house or by to the consultants. Some of these procedures were: (1) To discourage the usage of closed space beams. (2), Providing continuous deck slab for multispan bridges. (3) To maintain the existing practice of providing approach slabs at the abutments. (4) Providing retaining wall type abutments for bridges across rivers instead of bank seat types. The invert level of the pile cap must be at least 1 m below the existing bed level.

Cawangan Jalan, Ibu Pejabat JKR, K.L

2.10.3 Continuous Deck Slab For Multiple-Span Bridges After having recognised the problems associated with expansion joints, adoption of continuous deck slab for multi-span bridges was introduced. The expansion joints are probably only limited at the abutments. Adopting continuous concept and integral bridges whenever is possible in bridge superstructure construction may result in the reduction in maintenance liability associated with moving parts such as expansion joints and bearings. Last but not least, the public users now have a better riding quality associated with a lesser number of expansion joints and environmental noise disturbance reduced. Figure 2.12 shows one of the typical details of a continuous deck slab adopted over a pier.

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2.10.4 Retaining Wall Type Abutments

2.10.5 Approach Slab

The majority of the existing bridges were designed and constructed more than twenty years ago. The hydrological requirement required during the design stage was based on the existing hydrological parameters such as hydraulic gradient and type of vegetation. For the last twenty years, rapid development has taken place where jungles had been cleared and replaced with rubber and oil palm plantations. Hills had been flattened, valleys had been filled for the construction of roads, highways, and residential and industrial areas in the name of developments. As these developments have been taken place, hydrological parameters changed resulted in new set of water volume and flood levels. There were few occasions where the earthfill behind abutments were washed due to the limited flow area of the water. To overcome this problem in the future, only retaining wall type of abutment will be adopted for bridges spanning over the rivers. For the future deepening of the river, Drainage and Irrigation Department of Malaysia requires that all the soffit of the pile cap must be at least one metre below the existing bed level of the river.

In Malaysia, due to her climatic and geographical condition, it is a traditional practice to provide approach slabs at both ends of a bridge. Initially, the approach slab was located just below the wearing course. Due to the settlement at a few locations and the difficulties to maintain, the location of the approach slab was placed about l.Om below the wearing course surface.

Cawangan Jalan, Ibu Pejabat JKR, K.L

CHAPTER 3 - BRIDGE DESIGN STANDARD AND CODE OF PRACTICE 3.1 Code of Practices in Bridge Design - Malaysia In 1972, Limit State Design was first appeared in British Codes of Practice in the Building Code - CP 110. Since then it has been used in the water retaining structures codes (BS 5337) in 1976, the masonry code (BS 5628) in 1978 and finally the bridge code (BS 5400) in 1978. The introduction of limit state design of concrete bridges constitutes a radical change in the design philosophy because the existing design documents are written, principally, in

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terms of a working load and permissible stress design philosophy. Thus, the use f BS 5400 may change design procedures, though it is unlikely to change significantly the final sizes adopted for concrete bridges.

3.2

BS 5400

The Codes consist of the ten parts as listed in Table 3.1. It should be noted that BS 5400 is both a Code of Practice and a Specification. However, not all aspects of the design and construction of bridges are covered; exceptions worthy of mention are the design of parapets and such constructional aspects as expansion joints and water proofing. BS 5400

CODE

PART 1

GENERAL STATEMENT

PART 2

SPECIFICATION FOR LOADS

PART 3

CODE OF PRACTICE FOR DESIGN OF STEEL BRIDGES

PART 4

CODE OF PRACTICE FOR DESIGN OF CONCRETE BRIDGES

PART 5

CODE OF PRACTICE FOR DESIGN OF COMPOSITE BRIDGES

PART 6

SPECIFICATION FOR MATERIALS AND WORKMANSHIP, STEEL

PART 7

SPECIFICATION FOR MATERIALS AND WORKMANSHIP, CONCRETE, REINFORCEMENT AND PRESTRESSING TENDONS

PART 8

PART 9

RECOMMENDATIONS FOR MATERIALS AND WORKMANSHIP, CONCRETE, REINFORCEMENT AND PRESTRESSING TENDONS BRIDGE BEARINGS.

SECTION CODE OF PRACTICE FOR DESIGN OF 9.1 BRIDGE BEARINGS SECTION SPECIFICATION FOR MATERIALS, MAN9.2 UFACTURE AND INSTALLATION OF BRIDGE BEARINGS PART 10

CODE OF PRACTICE FOR FATIGUE

Table 3.1 -BS 5400

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Bridge Design For JKR Specification

The contents of the individual parts are summarised below: Part 1: The philosophy of limit state design is presented and the method of analysis which may be adopted are stated Part 2: Details are given of the loads to be considered for all types of bridges, the partial safety factors to be applied to each load and the load combinations to be adopted. Part 3: Design rules for steel bridges are given. Part 4: Design rules for reinforced, prestressed and composite (Precast plus insitu) concrete bridges are given in terms of material properties, design criteria and methods of compliance. Part 5: Design rules for steel-concrete composite bridges are given. Part 6: The Specification of materials and workmanship in connection with structural steelwork is given. Part 7: The Specification of materials and workmanship in connection with concrete, reinforcement and prestressing tendons is given. Part 8: Recommendations are given for the application of Part 7. Part 9: The design, testing and specification of bridge bearings are covered. Part 10: Loading for fatigue calculations and methods of assessing fatigue life are given.

3.3 Departmental Standard BD 37/88 - Loads for Highway Bridges 3.3.1 Introduction BSI committee CSB 59/1 has reviewed BS 5400: Part 2 1978 (including BSI Amendment No. l (AMD 4209) dated March 1983) and has Page 22

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agreed a series of major amendments including the revision of the HA loading curve. It has been agreed that as an interim measure, pending a long term review of BS 5400 as a whole and bearing in mind the current work on Eurocodes, the present series of amendments to Part 2 shall be issued by the Department of Transport, U.K rather than BSI. Because of the large volume of technical and editorial amendments involved it has also been decided that a full composite version of BS 5400: Part 2 including all the agreed revisions should be produced, and this forms and appendix to the Departmental Standard. 3.3.2 Additional Requirements 1. All road bridges shall be designed to carry HA loading. In addition, a minimum of 30 units of type HB loading shall be taken for all road bridges except for accommodation bridges which shall be designed to HA loading only. The actual number of units shall be related to the class of road as specified below: Class of road carried Number of units of type HB by structures loading Motorways and Trunk Roads (or principal road extensions of trunk routes)

45

Principal roads

337.5

Other public roads

33 0

3.4 Foundation Foundation shall follow British Standard Institution BS 8004: Foundation

3.5 Expansion Joints in Deck Slabs Expansion Joints in Bridge Decks shall follow Department of Transport Highways and Traffic Departmental Standard BD 33/88- Expansion Joints For Use in Highway Bridge Decks.

3.6 Parapet Parapet shall be of New Jersey type concrete structure and in accordance to Department of Transport (U.K) Technical Memorandum No.BE.5: The Design of Highway Parapets. The design of New Jersey concrete guardrail shall be in accordance to Arahan Teknik (Jalan) 1/85 (Pindaan 1/89) mannual on Guardrail of Longitudinal - Traffic Barrier.

3.7 Anti-Corrosion Protective System The steel materials used for the bridge structures shall follow BS 5400: Part 6. A comprehensive anti-corrosion protective system shall be in accordance with BS 5493 or equivalent.

3.8 2. For highway bridges where the superstructure carries more than seven traffic lanes (i.e. lanes marked on the running surface and normally used by traffic), application of type HA and type HB loading shall be agreed with the Authority (UK - Technical Approval Authority, Malaysia - JKR). 3. In determining the wind load and temperature effects for foot / cycle track bridges, the return period may be reduced from 120 years to 50 years subject to the agreement of the Authority (UK - Technical Approval Authority, Malaysia - JKR).

Cawangan Jalan, Ibu Pejabat JKR, K.L

Ship Impact

Appropriate ship collision forces shall be established and follow AASHTO Guide Specification and Commentary for Vessel Collision Design of Highway Bridges; 1991.

3.9

Elastomeric Bridge Bearings

The elastomeric bridge bearing shall be designed in accordance to BS 5400: Part 9.1 - Code of Practice for Design of Bridge Bearings. Elastomeric bearings shall be of natural rubber and in accordance with the specification proposed by the Committee on Natural Rubber in Construction, Rubber Page 23

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Research Institute, Malaysia.

3.10 Vehicle Collision Loads on Highway Bridge Supports and Superstructure Vehicle Collision Loads on Highway Bridge Supports and Superstructure shall be designed in accordance with BD 60/94.

CHAPTER 4 - DESIGN PRINCIPLE AND APPROACH 4.1 Introduction Rules and procedures for the design of bridges have been the subject of continuous amendment, improvement and development over the years. A significant development took place in 1967 when a meeting was held to discuss the revision of B.S 153, on which many bridge design documents were based. It was suggested that a unified code of practice should be written in .terms of limit state design which would cover steel, concrete and composite steel concrete bridge of any span. A number of subcommittees were formed to draft various sections of such a code; the work of these sub-committees has culminated in B.S 5400.

4.2

Limit State Design

Limit state design is a design process which aims to ensure that the structure being designed will not become unfit for the use for which it is required during its design life. The structure may reach a condition at which it becomes unfit for use for one of many reasons (e.g. collapse or excessive cracking) and each of these conditions is referred to as a limit state. In limit state design each limit state is examined separately in order to check that it is not attained. Assessment of whether a limit state is attained could be made on a deterministic or a probabilistic basis. In BS 5400, a probabilistic basis is adopted and, thus, each limit state is examined in order to check whether there is an

Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification acceptable probability of it not being achieved. Different acceptable probabilities are associated with the different limit states. The partial safety factors and design criteria are chosen to give similar levels of safety and serviceability to those obtained at present code. However, typical levels of risk in the design life of a structure are taken to be 10-6 against collapse and 10-2 against unserviceability occurring. Thus the chance of collapse occurring is made remote and much less than the chance of the serviceability limit state being reached. Limit state design principles have been agreed internationally and set out in International Standard ISO 2394 which becomes a document forms the basis of the limit state design philosophy of BS 5400.

4.3

Limits States

A limit state is a condition, which a structure or a part of a structure would become less than completely fit for its intended uses. Two limit states are considered in BS 5400; i) Ultimate Limit State ii) Serviceability Limit State 4.3.1 Ultimate Limit State Ultimate limit state is corresponding to the maximum load-carrying capacity of the structure or a section of the structure, and could be attained by: (i)Loss of equilibrium when a part or the whole of the structure is considered as rigid body. (ii) A section of the structure or the whole of the structure reaching its ultimate strength in terms of post-elastic or post-buckling behaviour. (iii) Fatigue failure. However, it can be seen that fatigue is considered not under ultimate loads but under a loading similar to that at the serviceability limit state. 4.3.2 Serviceability Limit State This denotes a condition beyond which a loss Page 24

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of utility or cause for public concern may be expected, and remedial action required. For concrete bridges the serviceability limit state is, essentially, concerned with crack control and stress limitations. In addition, the serviceability limit state is concerned with the vibrations of footbridges. 4.3.3 Design Life This is defined in BS 5400 as 120 years. However, The Code emphasises that this does not necessarily mean that a bridge designed in accordance with it will no longer fit for its purpose after 120 years, nor that it will continue to be serviceable for that length of time, without adequate and regular inspection and maintenance.

Bridge Design For JKR Specification = yf3 [effect of yfL Qx ] Where [Partial Load Factor] is a factor that takes account (i) inaccurate assessment of the effect of loading (ii) unforeseen stress distribution in the structure (iii) variation in dimensional accuracy achieved in construction Where linear relationships can be assumed between loading and load effects, S* = [effect of YS. Yn..QKI 4.4.4 Design Resistance (R*) R* = function (fk)/(YR,)

4.4 Loads 4.4.1 Nominal Load (Qx) Where adequate statistical distributions are available, nominal loads are those appropriate to a return period of 120 years. In the absence of such statistical data, nominal load values that are considered to appropriate to a 120 year return period are given.

or R* = function (fk-) (Ym) where fk = characteristic (or nominal) strength of material

4.4.2 Design Load (Q*) Q* = Yfl QK Where yfl = function (yfl . yf ) And yfl take account the possibility of unfavourable deviation of the loads from their nominal values yfz takes account acting together will all attain their nominal values simultaneously

Ym = reduction factor = function (Ym i . Ym2 ) where Ym1 is intended to cover the possible reductions in the strength of the materials in the structure as a whole as compared with the characteristic value deduced from the control test specimen. Ym2 is intended to cover possible weakness of the structure arising from any cause other than the reduction in the strength of the materials allowed for in Ym1, including manufacturing tolerances.

4.5 Partial Safety Factors 4.4.3 Design Load Effects (S*) S* = yf-,[effect of Q*] Cawangan Jalan, Ibu Pejabat JKR, K.L

The values of the partial safety factor Yn, to be applied at the ultimate and serviceability limit Page 25

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states for the various load combinations are given in Table 8.4. Followings are some of general points should be noted: (i)Larger values are specified for the ultimate than for the serviceability limit state. (ii) The values are less for reasonably well defined loads, such as dead load, than for more variable loads, such as live or superimposed dead load. Hence the greater uncertainty associated with the latter loads is reflected in the values of the partial safety factors. (iii) The value for a live load, such as HA load, is less when the load is combined with other loads, such as wind load in Load Combination 2 or temperature loading in Load Combination 3, than when it acts alone, as in Load Combination 1. This is because of the reduced probability that a number of loads acting together will all attain their nominal values simultaneously. This fact is allowed for by the partial safety factor Yrz, which is a component of Yo.. (iv) A value of unity is specified for certain loads (e.g. superimposed dead load) when this would result in a more severe effect. (v) The values for dead and superimposed dead load at the ultimate limit state can be different to the tabulated values.

4.6

Application of Loads

Bridge Design For JKR Specification tude. In the case of dead load this entails applying a yn. value of 1.0: it is emphasised that this value is applied to all parts of the dead load effect. In the case of superimposed dead load and live load, these loads should not be applied to those portions of the structure where their presence would diminish the load effect under consideration. Influence lines are frequently used in bridge design and, in view of the above, it can be seen that superimposed dead load and live load should be applied to the adverse parts of an influence line and not to relieving parts. It is not intended that parts of parts of influence lines should be loaded. 4.6.2 Overturning of Structure The stability of a structure against overturning is calculated at the ultimate limit state. The criterion is that the least restoring moment due to unfactored nominal loads should be greater than the greatest overturning moment due to design loads. 4.6.3 Foundations The soil mechanics aspects of foundations should be assessed in accordance with CP 2004, which is not written in terms of limit state design, Hence these aspects should be considered under nominal loads. However, when carrying out the structural design of a foundation, the reaction from soil should be calculated for the appropriate design loads.

4.6.1 General

4.7

The general philosophy governing the application of the loads is that the worst effects of the loads should be sought. In practice, this implies that the arrangement of the loads on the bridge is dependent upon the load effect being considered, and the critical section being considered. In addition, the Code requires that, when the most severe effect on a structural element can be diminished by the presence of a load on a certain portion of the structure, then the load is considered to act with its least possible magni-

4.7.1 Concrete

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Material Properties

Characteristic Strengths Material strengths are defined in terms of characteristic strengths. The characteristic cube compressive strength (f,-") of concrete is referred to as its grade, e.g. grade 40 concrete has a characteristic strength of 40 N/mm2. Grades 20 to 50 may be used for normal weight reinforced concrete and 30 to 60 for Page 26

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prestressed concrete.

4.8

Design Criteria

4.7.2 Reinforcement The design criteria are given in Part 4 : BS 5400 under the heading:

Characteristic Strengths The quoted characteristic strengths of reinforcement (fy) are 250 N/mm2 for mild steel; 410 N/mm2 for hot rolled high yield steel; 460 N/mm2 for cold worked high yield steel, except for diameters in excess of 16mm when it is 425 N/mm2 ; and 485 N/mm2 for hard drawn steel wire.

Š Ultimate limit state Š Serviceability limit state Š Other considerations

4.7.3 Prestressing Steel

Table 4.2 shows the list of the criteria from which it can be seen that there are a great number of criteria to be satisfied and, if calculation has to be carried out for each, the design procedure may be extremely lengthy.

Characteristic Strengths Tables are given for the characteristic strengths of wire, strand, compacted strand and bars of various nominal sizes. Each tabulated value is given as a force which is the product of the characteristic strength (fp,,) and the area (Aps) of the tendon. 4.7.4 Material Partial Safety Factors ym Values Design strengths are defined as characteristic strengths divided by the appropriate partial safety factors (ym). The ym values appropriate to the various limit states are summarised in Table 4.1. Limit State

Other considerations includes those criteria which are not specified in BS 5400 but which are, nonetheless, important in design terms

Limit State

Design Criteria

Ultimate Limit State

Rupture Buckling Overturning Vibration

Serviceability Limit State Steel Stress Limitations Concrete Stress Limitations Cracking of Prestressed Concrete Cracking of Reinforced Concrete Other Considerations

Deflections Fatigue Durability

Concrete Steel

Table 4.2 - Design Criteria Serviceability Limit State Analysis of Structure Reinforced Concrete Cracking Prestressed Concrete Cracking Stress Limitation Vibration

1.0 1.0 1.3 1.3 1.0

1.0 1.0 1.0 1.0 1.0

Ultimate Limit State Analysis of 'Structure Section Design

1.0 1.5

1.0 1.15

Deflection

1.0

1.0

Fatigue

1.3

1.0

Table 4.1 - ym Values

Cawangan Jalan, Ibu Pejabat JKR, K.L

4.8.1 Ultimate Limit State The criterion for rupture of one or more sections, buckling or overturning is simply that these events should not occur. A vibration criterion, which would be concerned with vibrations to cause collapse of a bridge, is not given, but, instead, compliance with the serviceability limit state vibration criterion is deemed to satisfy the ultimate limit state requirements.

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4.8.2 Serviceability Limit State

Bridge Design For JKR Specification

hypothetical tensile stresses exist at the maximum size of cracks.

(i) Steel Stress Limitations

(a) Serviceability limit state

It is generally only necessary to check cracks widths in bridges under HA loading for load combination 1. This means that there is an indirect check on reinforcement stresses under primary HA loading but not under other loads.

Loading

Allowable Stress

Bending Direct compression

0.33fcu (0.4f fcu at supports) 0.25 fi

(ii)Concrete Stress Limitations

Stress Distribution

Allowable Stress

Triangular Uniform

0.5fi 0.4fi

Concrete stress limitations include compressive stresses in reinforced and prestressed concrete, and compressive, tensile and interface shear stresses in composite construction.

(b) Transfer

Table 4.2 - Limiting Concrete Compressive Stresses in Prestressed Concrete

In order to prevent micro-cracking, spalling and unacceptable amounts of creep occurring under serviceability condition, compressive stresses are limited to 0.5 f"' for compressive stresses in reinforced concrete.

(iv) Cracking of Reinforced Concrete The design surface crack widths were assigned from considerations of appearance and durability. They are summarised in Table 4.3.

The limiting compressive stresses in prestressed concrete for the serviceability limit state and at transfer are given in Table 4.3.

4.8.3 yf3 Values

(iii) Cracking of Prestressed Concrete The criteria for the control of cracking in prestressed concrete are presented in terms of limiting flexural tensile stresses for three classes of prestressed concrete. Class 1: No tensile stresses are permitted except for 1 N/mm2 under prestress plus dead loads, and at transfer.

The nominal loads and the values of the partial safety factors yf., by which these loads are multiplied to give design loads. Then, the effects of the latter have to be multiplied by a partial safety factor yf3 in order to obtained design load effects. The values of yt3 are dependent upon the material of the bridge. The value of yr3 should be taken as 1.0 for serviceability limit state. For ultimate limit state, the value of yf3 should be taken as 1.10, except that where plastic methods are used for the analysis of the structure, yea should be taken as 1.15.

Class 2: The tensile stresses should not exceed the design flexural tensile strength of the concrete, which is 0.454fcu for pretensioned member and 0.36Jfcu for post tensioned members. Class 2: For Class 3 members in which cracking is allowed, it may be assumed that the concrete section is uncracked and that Cawangan Jalan, Ibu Pejabat JKR, K.L

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Bridge Design For JKR Specification

4.8.3 yf3 Values The nominal loads and the values of the partial safety factors yf., by which these loads are multiplied to give design loads. Then, the effects of the latter have to be multiplied by a partial safety factor yf3 in order to obtained design load effects. The values of yt3 are dependent upon the material of the bridge. The value of yr3 should be taken as 1.0 for serviceability limit state. For ultimate limit state, the value of yf3 should be taken as 1.10, except that where plastic methods are used for the analysis of the structure, yea should be taken as 1.15.

Cawangan Jalan, Ibu Pejabat JKR, K.L

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LIMIT STATE REQUIREMENTS

OTHER CONSIDERATIONS

SLS ULS

DEFLECTIONS

CRACKING

VIBRATION

RUPTURE OR INSTABILITY

FATIGUE STRESS LIMITATIONS

REINFORCED CONCRETE

IN CONCRETE

BUCKLING

DURABILITY

IN STEEL

PRESTRESSED CONCRETE OVERTURNING

VIBRATION

CLASS 1

CLASS 2

CLASS 3

Figure 4.1 - Design : Limit State Requirements

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4.9

Bridge Design For JKR Specification

Reaction Forces paths

4.9.1 Free-Fixed Single Span Bridge

Figure 4.4 shows the paths of reacting forces of a Fixed-Free Single Span Bridge. The vertical forces from the superstructure will be shared between the abutments. These loads and vertical loads from the abutments will be transferred to the pile caps and finally-will be supported by the pile foundation. The horizontal forces from the superstructure will be transferred to the abutment at the fixed joint. Depending on the direction of the horizontal forces, they may be resisted by the passive reactions at the abutment or the abutment wall will solely resist them. In normal practice, it is assumed that the stiff foundation where the piles are assumed to be pin jointed to the pile cap. At the toe of the abutment wall, the vertical and horizontal forces will be represented by the vertical forces acting at the centroid of the piles and a couple. The piles will resist the vertical forces and the couple. Normally, in the designing the pile foundation, the horizontal foundation will be resisted by the horizontal components of the raked piles while the vertical forces will be resisted by the vertical piles and the vertical components of the raked piles.

Cawangan Jalan, Ibu Pejabat JKR, K.L

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Figure 4.5 shows the paths of reacting forces of a Free-Fixed-Free Two Spans Bridge. The vertical forces from the superstructure will be shared between the pier and abutments. These loads and vertical loads from the abutments will be transferred to the pile caps and finally will be supported by the pile foundation. The horizontal forces from the superstructure will be transferred to the pier at the fixed joint. At the toe of the pier, the vertical and horizontal forces will be represented by the vertical forces acting at the centroid of the piles and a couple. The piles will resist the vertical forces and the couple.

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Figure 4.6 shows the paths of reacting forces of a three spans bridge. The vertical forces from the superstructure will be shared between the piers and abutments. The horizontal forces from the superstructure will be transferred to one of the piers, which is fixed to the superstructure.

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Figure 4.7 shows the paths of reacting forces of a four span bridge. The vertical forces from the superstructure will be shared between the piers and abutments. The horizontal forces from the superstructure will be transferred to the middle pier where is fixed to the superstructure.

Cawangan Jalan, Ibu Pejabat JKR, K.L

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4.10 Step By Step in Design Logically, steps in designing bridge components should follow the paths of reacting forces. Therefore, superstructure should be the first component to be determined and designed. Then follows by the design of abutment or pier pile caps and lastly the pile foundation. But this not really true in designing a bridge. In designing each component of a bridge, each one of them has its own unique requirements. Pier may be designed either as a column or as a reinforced concrete wall. On top of that column design may be designed either as a short or slender column. For either column or a reinforced concrete wall, the member should be designed to satisfy the Ultimate Limit State requirements and follows by the checking for Serviceability Limit State conditions. Similarly, abutment wall may be designed as cantilever beam or as a reinforced concrete wall depending on the configuration. For both cases, the member should be designed to satisfy the Ultimate Limit State requirements and follows by the checking for Serviceability Limit State limitations.

Bridge Design For JKR Specification

Due to the complex design requirements of each component of the bridge mentioned above, it is very difficult and troublesome to carry the design procedure as per path of reacting forces. The author suggested the steps to be followed in are as shown in Figure 4.8. It can be seen that initially the design has to be started by determining the dimension and designing of the superstructure. It follows by the design of pile foundation, pile caps, pier and/or abutment and finally designing of other bridge components. By referring to Figure 4.9, the process of design can be divided into three independent design processes, i.e. Design of Superstructure, Design of Pile Cap and Sub Structure and lastly Design of Other Bridge Components.

Slightly different from designing column and abutment wall, in designing pile cap, it requires to fulfil the flexural bending requirement and checking to satisfy the flexural and punching shears. Both flexural bending and shear designs are to the Ultimate Limit State requirements. Flexural bending and punching shears may be determined by reactions of piles. Therefore, pile number and arrangement and the reaction at each pile at the Ultimate Limit State must be determined and known before pile cap can be designed. In designing the pile foundation, the loads to be considered are only nominal loads, i.e. without any Factor of Safety. The factor of safety adopted in designing pile foundation is 2.0. In this case, validation of factor of safety will be carried during construction where the test load will be carried out. The test load will be twice the design load of the pile. Cawangan Jalan, Ibu Pejabat JKR, K.L

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Bridge Design For JKR Specification

Determine dimension of Superstructure

Design Superstructure

Determine dimension of Substructure

Determine All Loads 1) Live Loads 2) Dead Loads 3) Superimposed Dead Loads

Nominal Load

Design Load ( Multiplied by Factor of Safety)

Design Pile Foundation (1) Type of Pile (2) Number of Piles (Vertical + Rake) (3) Pile Arrangement

Design Substructure (1) Pile Cap + Pier (2) Pile Cap + Abutment

Design Other Bridge Components (1) Bearing (2) Dowels (3) Continuity Connection

Figure 4.8 - Sequence of Design

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CHAPTER 5 BRIDGE LOADING - PART I 5.1 Definitions Loads. External forces applied to the structure and imposed deformations such as those caused by restraint of movement due to changes in temperature. Axle loads Bending moments Shear forces Load effects. The stress resultants in the structure arising from to response to loads. Compressive stresses Flexural stresses Shear stresses Dead Load. The weight of the materials and parts of the structure that are structural elements, but excluding superimposed materials such as road surfacing, rail track ballast, parapets, mains, ducts, miscellaneous furniture, etc. Superimposed dead load. The weight of all materials forming loads on the structure that are not structural elements. Live loads. Loads due to vehicle or pedestrian traffic. Primary live loads. Vertical live loads, considered as static loads, due directly to the mass of traffic. Secondary live loads. Live loads due to changes in speed or direction of the vehicle traffic, eg. Lurching, nosing, centrifugal, longitudinal, skidding and collision loads. Adverse and relieving areas and effects. Where an element or structure has an influence line consisting of both positive and negative parts,

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in the consideration of loading effects which are positive, the positive areas of the influence line are referred to as adverse areas and their effects as adverse effects and the negative areas of the influence line are referred to as relieving areas and their effects as reliving effects. Conversely, in the consideration of loading effects which are negative, the negative areas of the influence line are referred to as adverse areas and their effects as adverse effects and the positive areas of the influence line are referred to as relieving areas and their effects as relieving effects. Total effects. The algebraic sum of the adverse and relieving effects. Dispersal. The spread of load through surfacing, fill, etc. Distribution. The sharing of load between directly loaded members and other members not directly load as a consequence of the stiffness of intervening connection members, as eg diaphragms between beams, or the effects of distribution of a wheel load across the width of a plate or slab.

5.2 Classification of Bridge Loads BD 37/88 divides the nominal loads into two groups, largely - Permanent Loads. - Transient Loads

5.3

Permanent Loads.

Permanents loads consist of dead loads, superimposed dead loads, loads due to filling materials, differential settlement and load derived from nature of the structural material. In the case of concrete bridges, the latter refers to shrinkage and creep of the concrete.

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5.3.1 Dead Load

Superimposed dead load on a bridge are:-

The nominal dead load will generally be calculated from the normal assumed values for the specific weight of material.

Premix Parapet Services (Water mains, lamp posts, etc)

Insitu concrete :24 kN/m3 Precast concrete :25 kN/m3 Premix :22.6 kN/m3 Backfill :18.9 kN/m3 Dead loads in the superstructure are : Beams Deck slab Diaphragm

5.3.3 Filling Materials The nominal loads due to the fill should be calculated by conventional principles of soil mechanics. The partial safety factor seem to be high due to the reason that the pressure on the abutments etc due to the fill are considered to be calculable only with a high degree of uncertainty, particularly for the conditions after construction.

Dead loads acting on the abutment are : Beams Deck slab Diaphragm Self weight of abutment Backfill Earth pressure Approach slab, approach slab, wearing course, backfill.

5.3.4 Shrinkage and Creep.

Dead loads acting on the pier are :

5.3.5 Differential Settlement.

Beams Deck slab Diaphragm Self weight of pier Backfill

The onus is placed upon the designer in deciding whether differential should be considered in detail.

Shrinkage and Creep only have to be taken into account when they are considered to be important. Obvious situations are where deflection are important and in the design of the articulation for a bridge.

5.3.2 Superimposed Dead Loads. The partial safety factor for superimposed dead load appears to be rather large. The reason for this is to allow for the fact that bridge decks are often resurfaced, with the result that the actual superimposed dead loads can be much greater than that assumed at the design stage.

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LOADS

PERMANENT LOADS

DEFERENTIAL SETTLEMENT

DEAD LOAD

TRANSIENT LOADS

LOADS DERIVED FROM THE NATURE OF THE STRUCTURAL MATERIAL

PRIMARY HIGHWAY LOADS

WIND LOADS

TEMPERATURE LOADS

HA

HA-UDL

CENTRIFUGAL LOADS

SUPERIMPOSED DEAD LOAD

EXCEPTIONAL LOADS

LOAD DUE TO FILLING MATERIAL

SECONDARY HIGHWAY LOADS

ERECTION LOADS

HB

HA-KEL

HA+HB

COLLISION WITH SUPPORTS

HB alone

LONGITUDINAL BRAKING

FATIGUE & DYNAMIC LOADS

SKIDDING

COLLISION WITH PARAPET

Figure 5.1 - Bridge Loading

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COMBINATION OF LOADS

PRINCIPAL COMBINATION

SECONDARY COMBINATION

LOAD COMBINATION 1

LOAD COMBINATION 2

LOAD COMBINATION 3

LOAD COMBINATION 4

LOAD COMBINATION 5

Permanent Loads + Appropriate Live Load

Permanent Loads + Appropriate Live Load + Wind Loads + Temporary Erection Loads

Permanent Loads + Appropriate Live Load + Pemperature Range & Difference + Temporary Erection Loads

Permanent Loads + Secondary Live Load + Wind Loads + Appropriate Primary Live Loads associated with them

Permanent Loads + Loads due to Friction at Bearings

Notes; 1. 2.

Application of Loads: Each element and structure shall be examined under the effect of loads that can coexist in each combination Selection to cause most adverse effect: Design loads shall be selected and applied in such a way that most adverse total effect is cause in the element or structure under consideration

Figure 5.2 - Load Combinations

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5.4

Transient Loads

All loads other than the permanent loads referred to above are transient loads. These consist of wind loads, temperature loads, exceptional loads, erection loads, the primary and secondary highway loading, footway and cycle track loading. Primary highways loading are vertical line loads, whereas the secondary loading is live load due to changes in speed or direction. Hence the secondary highway loading include centrifugal, braking, skidding and collision loads.

Bridge Design For JKR Specification

5.4.4 Erection Loads. At the serviceability limit state, it is required that nothing should be done during erection which would cause damage to the permanent structure, or which would alter its response in service from that considered I design. At the ultimate limit state, the Code considers the loads as either temporary or permanent and draws attention to the possible relieving effects of the former. The importance of the method of erection, and the possibility of impact or shock loading, are emphasized.

5.4.1 Wind Loads.

5.5 According to BS 5400, it is not necessary to consider wind loading in combination with temperature loading. In addition, as is also the case in BE 1/77, wind loading does not have to be applied to the superstructure of a beam and slab or slab bridges having a span less than 20m and a width greater than I Om. The designer has to decide mean hourly wind speed at the location where the bridge will be constructed.

Highway Bridge Live Loads.

Loans due to vehicle or pedestrian traffic. Live loads may be categorised as Primary Live Loads and Secondary Live Loads. Primary Live Loads. The primary live loads are vertical live loads, considered as static loads, due directly to the mass of traffic. Secondary Live Loads.

5.4.2 Temperature. There are, effectively, two aspects of temperature loading to be considered; namely the restraint to the overall bridge movement due to temperature range and the effects of temperature differences through the depth of bridge.

Secondary live loads are live loads due to changes in speed or direction of the vehicle traffic, e.g. lurching, nosing, centrifugal, longitudinal, skidding and collision loads.

5.4.3 Exceptional Loads. These include the loads due to otherwise unaccounted effects such as earthquakes, stream flows, impact due to ship etc.

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5.6

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Loads and Factors Specified

Nominal Loads Where adequate statistical distribution are available, nominal loads are those appropriate to a return period of 120 years. Design Loads Nominal loads shall be multiplied by the appropriate value of yfl, to derived the design load to be used in the calculation of moments, shears, total loads and other effects for each of the limit states under consideration. Additional Factor, yf3 Moments, shears, total loads and other effects of the design loads are also to be multiplied by yf3 to obtain the design load effects. In short, Design load = Nominal load x yf. x yt3

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Bridge Design For JKR Specification

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Bridge Design For JKR Specification

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Load Combination 5

5.8 Load Combinations There are three principal and two secondary load combinations of loads are specified.

For all bridges, the loads to be considered are: Š the permanent loads, Š loads due to friction at bearings

Load Combination 1 For all bridges, the loads to be considered are: Š the permanent loads, Š the appropriate primary live loads Load Combination 2 For highway and foot/cycle track bridges, the loads to be considered are: Š the permanent loads, Š the appropriate primary live loads Š loads due to wind Š temporary erection loads where erection is being considered Load Combination 3 For all bridges, the loads to be considered are: Š the permanent loads, Š the appropriate primary live loads Š loads arising from restraint due to the effects of temperature range and difference Š temporary erection loads where erection is being considered Load Combination 4 For highway bridges, the loads to be considered are: Š the permanent loads, Š the secondary live loads together with the appropriate primary live loads associated with them For foot/cycle track bridges, the loads to be considered are: Š the permanent loads, Š the only secondary live loads to be considered are the vehicle collision loads on bridge supports and superstructures Cawangan Jalan, Ibu Pejabat JKR, K.L

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CHAPTER 6

Bridge Design For JKR Specification

6.2 Relationship between carriageway and notional lanes.

BRIDGE LOADING - PART II 6.2.1 Carriageway widths of 5.00m or more. [Cl.3.2.9.3.1- BD 37/88]

6.1 Highway Carriageway, Traffic and Notional Lanes. [Cl. 3.2. 9 - BD 37/88] 6.1.1 Carriageway. [Cl.3.2.9.1 - BD 37/88] Carriageway is that part of the running surface which includes all traffic lanes, hard shoulders, hard strips and marker strips. The carriageway width is the width between raised kerbs. In the absence of raised kerbs it is the width between safety fences, less the amount of set-back required for these fences, being not less than 0.6m or more than 1.0m from the traffic face of each fence. The carriage width shall be measured in a direction at right angles to the line of the raised kerbs, lane marks or edge marking.

6.1.2 Traffic Lanes. [Cl. 3.2.9.2 - BD 37/88] Traffic lanes are the lanes that marked on the running surface of the bridge and are normally used by traffic.

6.1.3 Notional Lanes. [Cl. 3.2.9.3 - BD 37/88] The notional lanes are the notional parts of the carriageway used solely for the purposes of applying the specified live loads. The notional lane width shall be measured in a direction at right angles to the lane of the raised kerbs, lane marks or edge marking.

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Notional lanes shall be taken to be not less than 2.50m wide. Where the number of notional lanes exceeds two, their individual widths should be not more than 3.65m. The carriageway shall be divided into an integral number of notional lanes having equal widths as follows: Carriageway width m

5.00 up to and including 7.50 above 7.50 up to and including 10.95 above 10.95 up to and including 14.60 above 14.60 up to and including 18.25 above 18.25 up to and including 21.90

Number of notional lanes 2 3 4 5 6

Table 6.1- Carriageway and Notional Lanes [Table 14 -BD37/88]

6.2.2 Carriageway widths of less than 5.00m. [Cl. 3.2.9.2 - BD 37/88] The carriageway shall be taken to have one notional lane with a width of 2.50m. The loading (HA UDL and KEL) on the remainder of the carriageway shall be multiplied by the appropriate factors from Table 6.1 [Table 14 - BD 37/88] before being applied to the notional lanes indicated.

6.2.3 Dual Carriageway Structures. [Cl. 3.2. 9.3.3 - BD 37/88] Where dual carriageways are carried on one superstructure, the number of notional lanes on the bridge shall be taken as the sum of the number of notional lanes in each of the single carriageways as specified in Carriageway width of 5.00m or more above.

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6.3 Highway Bridge Live Loads. [CI. 6 - BD 37/88]

ii. Notional lanes, hard shoulders, etc. [CI. 6.1.2 - BD 37/88]

6.3.1 General [Cl. 6.1- BD 37/88]

The width and number of notional lanes, and the presence of hard shoulders, hard strips, verges and central reserves are integral to the disposition of HA and HB loading. Requirements for deriving the width and number of notional lanes for design purposes are specified in

Standard highway loading consists of HA and HB loading. HA loading is a formula loading representing normal traffic in Malaysia. HB loading is abnormal vehicle unit loading. Both loadings include impact.

6.1.3 [C1.3.2.9.3 - BD 37/88] i. Loads to be considered The structure and its elements shall be designed to resist the more severe effects of either:

Requirements for reducing HA loading for certain lane widths and loaded length are specified in

(1). Design HA loading, or (2). Design HB 45 units loading, or (3). Design HA loading combined with design HB 30 units loading.

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Bridge Design For JKR Specification

6.3.4.1 [Cl. 6.4.1 - BD 37/88] iii. Distribution analysis of structure [CI. 6.1.3 - BD 37/88] The effects of the design standard loadings shall, where appropriate, be distributed in accordance with a rigorous distribution analysis or from data derived from suitable tests.

ii. Nominal knife edge load (KEL) [Cl. 6.2.2 - BD 37/88] The knife edge load per notional lane shall be taken as 120 kN. iii. Distribution [CI. 6.2.3 - BD 37/88]

6.3.2 Type HA load ing[CI.6.2 - BD 37/88]

The UDL and KEL shall be taken to occupy one notional lane, uniformly distributed over the full width of the lane and applied as specified in 6.3Ai [Cl.6.4.1- BD 37/88]

Type HA loading consists of

iv.Dispersal [Cl. 6.2.4 - BD 37/88]

Š a uniformly distributed load (HA-UDL) and a knife edge load (HAKEL) combined, or Š a single wheel load.

No allowance for the dispersal of the UDL and KEL.

i. Nominal uniformly distributed load (UDL) [C1.6.2.1 - BD 37/88] a. Loaded lengths up to and including 50 meter, the UDL expressed in kN per linear meter of notional lane shall be derived from the equation,

W = 336(1/L)0.67 b. For loaded lengths in excess of 50 meter but less than 1600 meter, the UDL shall be derived from the equation,

v. Single Nominal Wheel Load alternative to UDL and KEL [Cl. 6.2.5 - BD 3 7/88] One 100 kN wheel, placed on the carriageway and uniformly distributed over a circular contact area assuming an effective pressure of 1.1 N/mm2 (i.e 340 mm diameter) shall be considered. Alternatively, a square contact area may be assumed, using the same effective pressure (i.e. 300 mm side).

iv.Dispersal [Cl. 6.2.6 - BD 37/88] W = 36 (1 /L)0.1

where L = the loaded length in meter W = the load per meter of notional lane in kN Values of the load per linear meter of notional lane are given in Table 6.2 and the load curve is illustrated in Figure 6.6.

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Dispersal of the single nominal wheel load at a spread-to-depth ratio of 1 horizontally to 2 vertically through asphalt and similar surfacing may be assumed, where it is considered that this may take place. Dispersal through structural concrete slab may be taken at a spread-to-depth ratio of 1 horizontally to 1 vertically down to the neutral axis.

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Loaded Length (m)

Load (kN/m)

Loaded Length (m)

2 4 6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

211.2 132.7 101.2 83.4 77.1 71.8 67.4 63.6 60.3 57.3 54.7 52.4 50.3 48.5 46.7 45.1 43.7 42.4

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Load (kN/m)

Loaded Length (m)

Load (kN/m)

41 42 43 44 45 46 48 50

27.9 27.5 27.0 26.6 26.2 25.8 25.1 24.4

41.1 40.0 38.9 37.9 36.9 36.0 35.2 34.4 33.7 33.0 32.3 31.6 31.0 30.5 29.9 29.4 28.9 28.4

Table 6.2 - Type HA -UDL (up to 50m)

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6.3.3 Type HB Loading [CI. 6.3 -BD 37/88]

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Š 30 when acting together with HA Š 45 when HB alone ii. Nominal HB Loading [C1.63.1 - BD 37/88]

i. General For all public highway bridges, the number of units of type FIB loading that shall be considered are:

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Figure 6.7 shows the plan and axle arrangement for one unit of nominal HB loading. One unit shall be taken as equal to 10 kN per axle (i.e. 2.5 kN per wheel)

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The overall length of the HB vehicle shall be taken as 10, 15, 20, 25 or 30 meter for inner axle spacings of 6, 11, 16, 21 or 26 meter respectively, and the effects of the most severe of these cases shall be adopted. The overall width shall be taken as 3.5 meter. The longitudinal axis of the HB vehicle shall be taken as parallel with the lane markings. iii. Contact Area [C1. 6.3.2 - BD 37/88] Nominal HB wheel loads shall be assumed to be uniformly distributed over a circular contact area, assuming effective pressure of 1.1 N/mm2. Alternatively, a square contact area may be assumed, using the same effective pressure.

construction, the maximum effect should be determined by consideration of the adverse area or combination of adverse areas using the loading appropriate to the full base length or the sum of the full base lengths of any combination of the adverse areas selected. Where the influence line has a cusped profile and lies wholly within a triangle joining the extremities of its base to its maximum ordinate, the base length shall be taken as twice the area under the influence line divided by the maximum ordinate. Therefore, Loaded length : the length of the base of the positive or negative portion of the influence line for a particular effect at the design point under consideration

iv.Dispersal [Cl. 6.3.3 - BD 37/88] ii. Single Span Dispersal of HB wheel loads at a spreadto-depth ratio of 1 horizontally to 2 vertically through asphalt and similar surfacing may be assumed, where it is considered that this may take place.

For a single span member, the loaded length for the span moment is the span length. i.e. Span length = L

Dispersal through structural concrete slabs may be taken at a spread-to-depth ratio of 1 horizontally to 1 vertically down to the neutral axis. iv.Design [Cl. 6.3.4 - BD 37/88] Load Combination

For Load Combination 1 For Load Combination 2 For Load Combination 3

yfi. For U.L.S

For S.L.S

1.30 1.10 1.10

1.10 1.00 1.00

6.3.3 Loaded Length

iii. Two Span Continuous member (Equal Span) The loaded length for calculating the support moment would be 2L (40m). (The loading = 26.2 kN/m) The loaded length for calculating the span moment would be L (20m). (The loading = 30.0 kN/m)

i. General The loaded length for the member under consideration shall be the full base length of the adverse area. Where there is more than one adverse area, as for example in continuous Cawangan Jalan, Ibu Pejabat JKR, K.L

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iv.Multi Span Member Four Span The support moment at Support B, would be calculated: Š by considering span AB and BC loaded with loading appropriate to a loaded length of 2L or Š by considering span AB, BC and DE loaded with loading appropriate to a loaded length of 3L The first case likely to be more severe for most cases. The moment in span BC, would be calculated considering Š span BC loaded with loading appropriate to the loaded length of L or Š span BC and DE loaded with loading appro priate to a loaded length of 2L

Bridge Design For JKR Specification

6.3.4 Application of Type HA Loading [ Cl. 6.4 - BD 37/88] i. Type HA Loading [ Cl. 6.4.1- BD 37/88] Type HA UDL determined for the appropriate loaded length and type HA KEL loads shall be applied to each notional lane in the appropriate parts of the influence line for the element or member under consideration. The lane loadings are interchangeable between the notional lanes and a notional lane or lanes may be left unloaded if this caused the most severe effect on the member or element under consideration. The KEL shall be applied at one point only in the loaded length of each notional lane. Where the point under consideration has a different influence line for the loading in each lane, the appropriate loaded length for each lane will vary and the lane loadings shall be determined individually. HA Lane Factors [ Cl. 6.4.].1 - BD 37/88] The HA UDL and HA KEL shall be multiplied by the appropriate factors from Table 6.3 before being applied to the notional lanes indicated.

Table 6.3 - HA Lane Factors [Table 14 - BD 3 7/88]

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Note: 1. a, = 0.274 bL and cannot exceed 1.0 a~ = 0.0137 [ bL(40-L) + 3.65(L-20)] where bL is the notional lane width (m) 2. N shall be used to determine which set of HA lane factors is to be applied for loaded lengths in excess of 50m. The value of N is to be taken as the total number of notional lanes on the bridge (this shall include all the lanes for dual carriageway roads) except that for a bridge carrying one-way traffic only, the value of N shall be taken as twice the number of notional lanes on the bridge.

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Where the carriageway has a single notional lane as specified in C1.3.2.9.3.2 - BD 37/88, the HA UDL and HA KEL applied to that lane shall be multiplied by the appropriate first lane factor for a notional lane width of 2.50m. The loading on the remainder of the carriageway width shall be taken as 5 kN/m2.

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Bridge Design For JKR Specification point only in the loaded length.

Multilevel Structures [ Cl. 6.4.1.2 - BD 37/88] Where multilevel superstructures are carried on common substructure members (such as column of a multilevel interchange) the most severe effect at the point under consideration shall be determined from Type HA loading applied in accordance with 6.3.4.1. Type HA Loading [C1.64.1 - BD 37/88]. The number of notional lanes to be considered shall be the total number of lanes, irrespective of their level, which contribute to the load effect at that point. Transverse Cantilever Slabs [ Cl. 6.4.1.3 - BD 37/88] Transverse cantilever slabs, slabs supported on all four sides and slabs spanning transversely. HA UDL and KEL shall be replaced by the arrangement of HB loading given in Cl. 6.4.3.1 - BD 37/88. Combined Effects [Cl. 6.4.1.4 - BD 37/88] Where elements of a structure can sustain the effects of live load in two ways, i.e. as elements in themselves and also as parts of the main structure (eg. The top flange of a box girder functioning as a deck plate), the element shall be proportioned to resist the combined effects of the appropriate loading in C1.6.4.2 - BD 37/88. Knife Edge Load (KEL) [Cl. 6. 4.1.5 - BD 37/88] The KEL shall be taken as acting as follows: (1) On Plates. On plates, right slabs and skew slabs spanning or cantilevering longitudinally: in a direction which has the most severe effect. The KEL for each lane shall be considered as acting in a single line in that lane and having the same length as the width of the notional lane and the intensity set out in C1.6.4.1.1. As specified in C1.6.4.1.i, the KEL shall be applied at one Cawangan Jalan, Ibu Pejabat JKR, K.L

(2) On longitudinal members and stringers. On longitudinal member and stringers: in a direction parallel to the supports. (3) On piers, abutments and on other members supporting the superstructure. On piers, abutments and on other members supporting the superstructure: on the deck, parallel to the line of the bearings. (4) On cross members, including transverse cantilever brackets. On cross members, including transverse cantilever brackets: in a direction in line with the span of the member ii. Types HA and HB Loading Combined [Cl. 6.4.2 - BD 37/88] Type HA and HB loading shall be combined and applied as follows: (1) Type HA loading shall be applied to the notional lanes of the carriageway in accordance with 6.4. Li, modified as given in (2) below. (2) Type HB loading shall occupy any transverse position on the carriageway, either wholly within one notional lane or straddling two or more notional lanes. Where the FIB vehicle lies wholly within the notional lane or where the HB vehicle lies partially within a notional lane and the remaining width of the lane, measured from the side of HB vehicle to the edge of the notional lane, is less than 2.5 meters, type HB loading is assumed to displace part of the HA loading in the lane or straddled lanes it occupied. No other live loading shall be considered for 25 meters in front of the leading axle to 25 meters behind the rear axle of the HB vehicle. The remainder of the loaded length of the lane or lanes thus occupied by the HB vehicle shall be loaded with HA UDL only; HA KEL shall be omitted. The intensity of the HA UDL in these lanes shall be appropriate to the loaded length that includes the total length displaced by the type HB loading with the front and rear 25 meter clear spaces. Page 60

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Where the HB vehicle lies partially within a notional lane and the remaining width of the lane, measured from the side of the.HB vehicle to the far edge of the notional lane, is greater or equal to 2.5 meters, the HA UDL loading in that lane shall remain but shall be multiplied by an appropriate lane factor for a notional lane width of 2.5 meters irrespective of the actual lane width; the HA KEL shall be omitted. Only one HB vehicle shall be considered on any one superstructure or on any substructure supporting two or more superstructure. iii. Highway loading on transverse cantilever slabs, slabs supported on all four sides, slabs spanning transversely and central reserves [ CI. 6. 4.3 - BD 37/88] Type HB loading shall be applied to the elements specified below, (1) Transverse cantilever slabs, slabs supported on all four sides and slabs spanning transversely. These elements shall be so proportioned as to resist the effects of the appropriate number of units of type HB loading occupying any transverse position in the carriageway or placed in one other notional lane. Proper other notional lane. Proper consideration shall be given to transverse joints of transverse cantilever slabs and to the edges of these slabs because of the limitations of distribution This does not apply to members supporting these elements.

Bridge Design For JKR Specification

iv.Standard Footway and Cycle Track Loading [ CI. 6.5 - BD 37/88] The live load on highway bridges due to pedestrian traffic shall be treated as uniformly distributed over footway and cycle tracks. For elements supporting footways or cycle tracks, the intensity of pedestrian live load shall vary according to the loaded length and any expectation of exceptional crowds. Reductions in pedestrian live load intensity may be made for elements supporting highway traffic lanes as well as footways or cycle tracks. Reductions may also be made where the footway (or footway and cycle track together) has a width exceeding two meters.

6.4

Secondary Live Loads

6.4.1 Accidental Wheel Loading [ C1.6.6 - BD 37/88] The elements of the structure supporting outer verges, footways or cycle tracks are not protected from vehicular traffic by an effective barrier, shall be design to sustain local effects of the nominal accidental wheel loading. i. Nominal accidental wheel loading [ C1.6.6.1-BD 37/88] The accidental wheel loading having the plan, axle and wheel load arrangement shown in Figure 6.11 shall be selected and located in the position which produces the most adverse effects on the elements. Where the application of any wheel or wheels has a relieving effect, it or they shall be ignored. ii. Contact area [ C1.6.6.2 - BD 37/88]

(2) Central reserves On dual carriageways the portion of the central reserve isolated from the rest of the carriageway either by a raised kerb or by safety fences is not required to be loaded with live load in considering the overall design of the structure, but it shall be capable of supporting 30 units of HB loading. Cawangan Jalan, Ibu Pejabat JKR, K.L

Nominal accidental wheel loads shall be assumed to be uniformly distributed over a circular contact area, assuming an effective pressure of 1.1 N/mm Z. Alternatively, a square contact area may be assumed, using the same effective pressure.

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iii. Dispersal [ CL. 6.6.3 - BD 37/88] Dispersal of accidental wheel loads at a spread-to-depth ratio of 1 horizontally to 2 vertically through asphalt and similar surfacing may be assumed, where it is considered that this may take place. Dispersal through structural concrete slabs may be taken at a spread-to-depth ratio of 1 horizontally to 1 vertically down to the neutral axis.

Accidental wheel loading need not be considered in Load Combinations 2 and 3. No other primary live load is required to be considered on the bridge.

v. Design Load [ C1.6.6.5 - BD 37/88]

For Load Combination 1

This Section refers to the load effects resulting from a collision with a parapet, locally on the structural elements in the vicinity of the parapet supports and globally on bridge superstructures, bearing, and substructures and retaining walls and wing walls. Rules for design the highway parapets including requirements for high level of containment parapets are set out in BS 6779 : Part 2.

iv.Live Load Combination [ C1.6.6.4 - BD 37/88]

Load Combination

6.4.2 Loads due to Vehicle Collision with Parapets [ C1. 6.7- BD 37/88]

yfL For U.L.S

For S.L.S

1.50

1.20

Cawangan Jalan, Ibu Pejabat JKR, K.L

The local effects of vehicle collision with parapets shall be considered in the design of elements of the structure supporting parapets by application of the loads given in (i) below. The global effects of vehicle collision with high level of containment parapets shall be considered in the design of bridge superstructures, bearings, substructures and retaining walls and wing walls by application of loads given in (ii) below. The global effects of vehicle collision with other types or parapets need not be considered. (i)Loads due to vehicle collision with parapets for determining local effects. [C1.6.7.1- BD 37188]

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1. Nominal Loads. [ C1.6.7.1.1- BD 37188] In the design of the elements of the structure supporting parapets, the following loads shall be regarded as the nominal load effects to be applied to these elements according to the parapet type and construction. For concrete parapets (High and normal levels of containment) The calculated ultimate design moment of resistance and the calculated ultimate design shear resistance of a 4.5 meter length of parapet at the parapet base applied uniformly over any 4.5 meter length of supporting element. For metal parapets (High, normal and low levels of containment)

Bridge Design For JKR Specification 3. Load Combination [ C1.6. 7.1.3 - BD 37/88 ] Loads due to vehicle collision with parapets for determining local effects shall be considered in Load Combination 4 only, and need not be taken as coexistent with other secondary live loads. 4. Design Load [ C1.6. 7.1.4 - BD 37/88] For determining local effects on elements supporting the parapets, yn. factors to be applied to the nominal load due to vehicle collision with the parapet and the associated nominal primary live load shall be taken as follows:

(a). The calculated ultimate design moment of resistance of a parapet post applied at each base of up to three adjacent posts and (b). the lesser of the following: i. the calculated ultimate design moment of resistance of a parapet post divided by the height of the centroid of the lowest effective longitudinal member above the base of the parapet applied at each base of up to any three adjacent parapet posts;

(ii) Loads due to vehicle collision with high level of containment parapets for determining global effects [ C1.6. 7.2 - BD 37188] 1. Nominal Loads [ C1.6.7.2.1- BD 37188 ]

ii. the calculated ultimate design shear resistance of a parapet post applied at each base up to any three adjacent parapet posts.

In the design of bridge superstructures, bearings, substructures, retaining walls and wing walls, the following nominal impact loads shall be applied at the top of the traffic face of high level of containment parapets only.

In the case of all high level of containment parapets, an additional single vertical load of 175 kN shall be applied uniformly over length of 3 meter at the top of the front face of the parapet. The loaded length shall be in that position which will produce the most severe effect on the member under consideration.

(a) a single horizontal transverse load of 500 kN; (b) a single horizontal longitudinal load of 100 kN; (c) a single vertical load of 175 kN.

2. Associated nominal primary live load [ C1.6.7.1.2 - BD 37188] The accidental wheel load specified in Section 9.4.1 shall be considered to act with the loads due to vehicle collision with parapets. Cawangan Jalan, Ibu Pejabat JKR, K.L

The loads shall be applied uniformly over a length of 3 meter measured along the line of the parapet. The loaded length shall be in that position which will produce the most severe effect on the part of the structure under consideration.

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Bridge Design For JKR Specification

2. Associated nominal primary live load [ C1.6.7.2.2 -BD 37/88] Type HA and the accidental wheel loading, shall be considered to act with the load due to vehicle collision on high level of containment parapets. The type HA and the accidental wheel loading shall be applied in accordance with Section 9.3.5 - Application of Types HA and HB Loading and Section 9.4.1.i - Nominal accidental wheel loading, respectively and such that they will have the most severe effect on the member under consideration. They may be applied either separately or in combination.

4. Design Load

3. Load Combination

The load due to vehicle collision with high level of containment parapets for determining global effects on bridge superstructures, substructures, non-elastomeric bearings, retaining walls and wing walls need only be considered at the ultimate limit state. In the case of elastomeric bearings however, the load due to vehicle collision with high level of containment parapets for determining global effects should only be considered at the serviceability limit state.

Loads due to vehicle collision with high level of containment parapets for determining global effects shall be considered in Load Combination 4 only, and need not be taken as coexistent with other secondary live loads.

The yf, values to be applied to the nominal load due to vehicle collision with high level of containment parapets and the associated nominal primary live load shall be taken as follows:

*Note: The yn, value of 1.4 shall only be used for small and light structures (such as some wing walls cantilevered off abutments, low light retaining walls, very short span bridge decks) where the attenuation of the collision loads is unlikely to occur. For other structures, account may be taken of the dynamic nature of the force and its interaction with the mass of the structure by application of the reduced ya, values given above.

Cawangan Jalan, Ibu Pejabat JKR, K.L

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6.4.3 Vehicle collision loads on highway bridge supports and superstructures [C1. 6.8 - BD 37/88 ] Where bridges over carriageways have piers located within 4.5 meter of an edge of the carriageway (Refer to 6.2.1 [Cl.3.2.9.2 - BD 37188] and Figure 1 - BD 37188), these shall be designed to withstand vehicle collision loads. Vehicle collision loads on abutments need not be considered. Where bridges over carriageways have a headroom clearance of less than 5.7 meter, the vehicle collision load on superstructures shall be considered.

Bridge Design For JKR Specification

(iii) Associated nominal primary live load [ C1.6.8.3 - BD 37/88] No primary live load is required to be considered on the bridge.

(iv) Load Combination [ C1.6.8.4 - BD 37/88 ] Vehicle collision loads on supports and on superstructures shall be considered separately, in Load Combination 4 only, and need not be taken as coexistent with other secondary live loads. (v) Design Load [ Cl. 6.8.5 - BD 37/88 ]

(i)Nominal load on supports [ C1. 6.8.1-BD 37/88 ] The nominal loads are given in Table 9.15 together with their direction and height of application, and shall be considered as acting horizontally on bridge supports. All of the loads given in Table 9.15 shall be applied concurrently. The loads shall be considered to be transmitted from the safety fence provided at the supports with residual loads acting above the safety fence.

For all elements excepting elastomeric bearings, the effects due to vehicle collision loads on supports and on superstructures need only be considered at the ultimate limit state. The Yf, to be applied to the nominal loads shall have a value of 1.50. For elastomeric bearings, the effects due to vehicle collision loads on supports and on superstructures should be only considered at the serviceability limit state. The yfL to be applied to the nominal loads shall have a value of 1.00. (vi) Bridges crossing railway track, canals or navigable water [ C1.6.8.6-BD 37/88] Collision loading on bridges shall be as agreed with the appropriate authority.

(ii) Nominal load on superstructures [ C1.6.8.2 - BD 37/88 ] A single nominal load of 50 kN shall be considered to act as a point load on the bridge superstructure in any direction between the horizontal and the vertical. The load shall be applied to the bridge soffit, thus precluding a downward vertical application. Given that the plane of the soffit may follow a superelevated or non-planar form, the load can have an out ward or inward application.

Cawangan Jalan, Ibu Pejabat JKR, K.L

6.4.4 Centrifugal Loads [ C1.6.9-BD 37/88] On highway bridges carrying carriageway with horizontal radius of curvature less than 1000 meter, centrifugal loads shall be applied in any two notional lanes in each carriageway at 50 meter centres. If the carriageway consists of one lane only, centrifugal loads shall be applied at 50 meter in that lane

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(i)Nominal centrifugal load [ C1.6.9.1- BD 37/88]

1. Nominal Load for Type HA [ C1.6.10.1- BD 37/88]

A nominal centrifugal load F., shall be taken as: 40000 F = r+ 150 kN

The nominal load for HA shall be 8 kN/m of loaded length plus 250 kN, subject to a maximum of 750 kN, applied to an area one notional lane width x the loaded length.

where, r : the radius of curvature of the lane in meter. A nominal centrifugal load shall be considered to act as a point load, acting in a radial direction at the surface of the carriageway and parallel to it. (ii) Associated nominal primary live load j C1.6.9.2 - BD 37/88] With each centrifugal load there shall also be considered a vertical live load of 400 kN, distributed over the notional lane for a length of 6 meter.

2. Nominal Load for Type HB [ C1.6.10.2 - BD 37/88] The nominal load for HB shall be 25% of the total nominal HB load adopted, applied as equally distributed between the eight wheels of two axles of the vehicle, 1.8 meter apart. 3. Associated Nominal Primary Live Load [ C1.6.10.3 -BD 37/88] Type HA or HB load, applied in accordance with ii. Application of Types HA and HB Loading, shall be considered to act with longitudinal load as appropriate.

(iii) Load Combination [ Cl.6.9.3 - BD 37/88 ] 4. Load Combination [ C1.6.10.1- BD 37/88] Centrifugal loads shall be considered in Load Combination 4 only and need be taken as coexistent with other secondary live loads.

Longitudinal load shall be considered in Load Combination 4 only and need not be taken as coexistent with other secondary live loads.

(iv) Design Load [ C1.6.9.4 - BD 37/88 ] 5. Design Load [ C1.6.10.4- BD 37/88] For the centrifugal loads and primary live loads, yfL shall be taken as follows: For the ultimate limit state For the serviceability limit state

: 1.50 : 1.00

6.4.5 Longitudinal Load [ C1.6.10 - BD 37/88] The longitudinal load resulting from traction or braking of vehicles applied at the road surface and parallel to it in one notional lane only shall be taken as the more severe design load resulting from the following: Š Nominal load for Type HA Š Nominal load for Type HB Š Design Load Cawangan Jalan, Ibu Pejabat JKR, K.L

yfL Type of Load For U.L.S

For S.L.S

For HA Load 1.25

1.25

1.00

For HB Load 1.10

1.10

1.00

6.4.6 Accidental Load Due to Skidding [ C1.6.11- BD 37/88] On straight and curved bridges a single point load shall be considered in one notional lane only, acting in any direction on and parallel to, the surface of the highway. i. Nominal Load [ C1.6.11.1-BD 37/88] Page 66

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FOR INTERNAL USE ONLY

The nominal load shall be taken as 300 kN. ii. Associated Nominal Primary Live Load [ C1.6.11.2 - BD 37/88] Type HA loading, applied in accordance with 6.3.4.1. Type HA Loading [C1.64.1 - BD 37/88], shall be considered to act with the accidental skidding load. iii. Load Combination [ C1.6.11.3 - BD 37/88] Accidental load due to skidding shall be considered in Load Combination 4 only, and need not be taken as coexistent with other secondary live loads. iv.Design Load [ C1.6.11.4 - BD 37/88] yfL

Load Combination For U.L.S For Load Combination 4 1.25

For S.L.S 1.00

Wind loading will not be significant in its effect on a large proportion of bridges, such as concrete slab or slab and beam structures 20 meter or less in span, 10 meter or more in width and at nominal height above ground In general, a suitable check for bridges in normal circumstances would be to consider a wind pressure of 6 kN/m2 applied to the vertical projected area of the bridge or structural element under consideration, neglecting those areas where the load would be beneficial. 6.5.2 Wind Gust Speed [C1.5.3 - BD 37/88] i. Maximum wind gust speed on bridges without live load, v, [ C1.5.3.2.1 - BD 37188] Maximum wind gust speed on those parts of the bridge or its element on which` the application of wind loading increases the effect being considered shall be taken as: v, = V KI S, S2

6.4.7 Dynamic Loading on Highway Bridges [ C1.6.13 - BD 37188 ] The effects of vibration due to live load are not normally required to be considered. However, special consideration shall be given to dynamically sensitive structures.

6.5 Wind Load [ C1.5.3 - BD 37/88 ] 6.5.1 General Wind pressure on a bridge depends on the geographical location, the local topography, the height of the bridge above ground, and the horizontal dimensions and cross section of the bridge or element under consideration. The maximum pressures are due to gusts that cause local and transient fluctuations a bout the mean wind pressures. Design gust pressures are derived from mean hourly wind speed. In Malaysia, mean hourly wind speed of 40 m/sec is adopted. Cawangan Jalan, Ibu Pejabat JKR, K.L

Where v : the mean hourly wind speed 40 m/sec K1 : a wind coefficient related to the return period 1.0 for highway, railway and foot/cycle track bridges for a return period of 120 years : 0.94 for foot/cycle track bridges for a return period of 50 years : 0.95 for erection period, that is corre sponding to a return period of 10 years S1 : the funneling factor : 1.0 for general cases : > 1.1 in valleys where local funnelling of the wind occurs, or where a bridge is situated to the lee of a range of hills causing local acceleration of wind S2 : the gust factor : as shown in Table 6.4

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ii. Minimum wind gust speed on relieving areas of bridges without live load, v'c Where wind on any part of a bridge or element gives relief to the member under consideration, the effective coexistent value of minimum wind gust speed v'c on the parts affording relief shall be taken as:

Bridge Design For JKR Specification

gives relief to the member under consideration, the effective coexistent value of wind gust speed v'c on the parts affording relief shall be taken as: 35 x K2/S2 m/sec or

v KI K2 m/sec which ever is lesser for highway and foot/cycle track bridges

v'C=vK1 K2 Where K2 :

the hourly speed factor as given in Table 6.4

6.5.3 Nominal transverse wind load, Pt [C1.5.3.3 - BD 37/88] i. Nominal transverse wind load, Pt (N)

iii. Maximum wind gust speed on bridges with live load, vc The maximum wind gust speed on those parts of the bridge or its elements on which the application of wind loading increases the effect being considered shall be taken as:

The nominal transverse wind load shall be taken as acting at the centroids of the appropriate areas and horizontally unless local conditions change the direction of the wind, and shall be derived from: Pt =qAl CD

v, = v KI SI S2 for highway and foot/cycle track bridges but not exceeding 35 m/sec iv.Minimum wind gust speed on relieving areas of bridges with live load, v'c Where wind on any part of a bridge or element

Cawangan Jalan, Ibu Pejabat JKR, K.L

where q : the dynamic pressure head 0.613 v,2 in N/m2 with v, in m/sec AI : the solid area (in m2) CD : the drag coefficient

ii. Area A1

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The area of the structure or element under consideration shall be the solid area in normal projected elevation derived as followings. a. Erection stages for all bridges The area A1 at all stages of construction shall be the appropriate unshielded solid area of the structure or element.

Bridge Design For JKR Specification

Where there are more than two parapets or safety fences, irrespective of the width of the superstructure, only those two elements having the greatest unshielded effect shall be considered.

(ii) For superstructures with solid parapets: b. Highway bridge superstructures with solid elevation For the superstructures with or without live load, the area A, shall be derived using the appropriate value of d as given in Table 6.5.

The superstructure, using depth d2 from Table 6.5 which includes the effects of windward and leeward parapets. Where there are safety fences or additional parapets, Pt shall be derived separately for the solid areas of the elements above the top of the solid windward parapet.

Š Superstructures without live load Pt shall be derived separately for areas of the following elements (i)For superstructures with open parapets: - the superstructure, using depth dl from Table 6.5; - the windward parapet or safety fence; - the leeward parapet or safety fence.

Cawangan Jalan, Ibu Pejabat JKR, K.L

Š Superstructures with live load Pt shall be derived for the area A, as given in Table 6.5 which includes the effects of the superstructure, the live load and the windward and leewards parapets. Where there are safety fences or leeward parapets higher than the live load depth dL, Pt shall be derived separately for the solid areas of the elements above the live load.

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Š Superstructures separated by an air gap Where two generally similar superstructures are separated transversely by a gap not exceeding 1 meter, the nominal load on the windward structure shall be calculated as if it were a single structure, and that on the leeward superstructure shall be taken as the difference between the loads calculated for the combined and the windward structures. Where the superstructures are dissimilar or the air gap exceeds 1 meter, each superstructure shall be considered separately without any allowance for shielding. c. Foot/cycle track bridge superstructures width solid elevation Š Superstructures without live load Where the ratio b/d as derived from Table 5 - BD 37/88 is greater than, or equal to, 1.1, the area A, shall comprise the solid area in normal projected elevation of the windward exposed face of the superstructure and parapet only. Pt shall be derived for this area, the leeward parapet being disregarded. Where b/d is less than 1.1, the area A, shall be derived as specified in b. Highway bridge superstructures with solid elevation, above. Š Superstructures with live load Where the ratio b/d as derived from Table 5 - BD 37/88 is greater than, or equal to, 1.1, the area A, shall comprise the solid area in normal projected elevation of the deck, the live load depth (taken as 1.25 meter above the footway) and the parts of the windward parapet more than 1.25 meter above the footway. Pt shall be derived for this area, the leeward parapet being disregarded. Where b/d is less than 1.1, the area A, shall be derived as specified in b. Highway bridge superstructures with solid elevation, above.

Bridge Design For JKR Specification The area A, for each truss, parapet, etc shall be the solid area in normal projected elevation. The area A, for the deck shall be based on the full depth of the deck. P1 shall be derived separately for the areas of the following elements: - the windward and leeward truss girders; - the deck; - the windward and leeward parapets; except that Pt need not be considered on projected areas of. - the windward parapet screened by the windward truss, or vise versa; - the deck screened by the windward truss, or vise versa; - the leeward truss screened by the deck; - the leeward parapet screened by the leeward truss, or vise versa. Š Superstructures with live load The area A, for the deck, parapet, trusses, etc shall be as for the superstructure without live load. The area A, for the live load shall be derived using the appropriate live load depth dL as given in Table 6.5. Pt shall be derived separately for the areas of the following elements: - the windward and leeward truss girders; - the deck; - the windward and leeward parapets; - the live load depth; except that PC need not be considered on projected areas of - the windward parapet screened by the windward truss, or vise versa; - the deck screened by the windward truss, or vise versa; - the live load screened by the windward truss or the parapet; - the leeward truss screened by the live load and the deck; - the leeward parapet screened by the leeward truss and the live load; - the leeward truss screened by the leeward parapet and the live load.

d. All truss girder bridge superstructures Š Superstructures without live load Cawangan Jalan, Ibu Pejabat JKR, K.L

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e. Parapets and safety fences For open and solid parapets and fences, P, shall be derived for the solid area in normal projected elevation of the element under consideration.

Bridge Design For JKR Specification beam or box girder above, where n is the number of beams or box girders. c. Single plate girder CD shall be taken as 2.2.

f. Piers

d. Two or more plate girders.

Pt shall be derived for the solid area in normal projected elevation for each pier. No allowance shall be made for shielding.

CD for each girder shall be taken as 2.2 without any allowance for shielding. Where the combined girders are required to be considered, CD for the combined structure shall be taken as 2(1 + c/20d), but not more than 4, where c is the distance centre to centre of adjacent girders, and d is the depth of the windward girder.

iii. Drag coefficient CD for erection stages for beams and girders. [C1.5.3.3.2 - BD 37/88] Followings are requirements for discrete beams or girders before deck construction or other infilling (e.g. shuttering) a. Single beam or box girder CD shall be derived from Figure 6.12 [Figure 5 - BD 37/88] in accordance with the ratio b/d.

iv. - Drag coefficient CD for all superstructures with solid elevation. For superstructures as shown in Figure 3 - BD 37/88, with or without live load, CD shall be derived from Figure 6.12 in accordance with the ratio b/d as derived from Table S - BD 37/88. v. Drag coefficient CD for all truss girder superstructures a. Superstructure without live load The drag coefficient CD for each truss and for the deck shall be derived as follows:

b. Two or more beams or box girders CD for each beam or box shall be derived from Figure 9.3 without any allowance for shielding. Where the combined beams or boxes are required to be considered, CD shall be derived as follows: Where the ratio of the clear distance between the beams or boxes to the depth does not exceed 7, CD for the combined structure shall be taken as 1.5 times CD derived as specified in a. - Single beam or box girder above. Where the ratio is greater than 7, CD for the combined structure shall be taken as n times the value derived as specified in a. - Single Cawangan Jalan, Ibu Pejabat JKR, K.L

1. For a windward truss,CD shall be taken from Table 6.6 Solidity For flatsided For round members where d is ratio members diameter of member 0.1 0.2 0.3 0.4 0.5

1.9 1.8 1.7 1.7 1.6

dv, < 6 m2/sec or 1.2 dvc' 1.2 1.2 1.1 1.1

dv, >- 6 m2/sec or 0.7 dvc' 0.8 0.8 0.8 0.8

Table 6.6 - Drag coefficient CD for a single truss [Table 6 - BD 37/88]

The solidity ratio of the truss is the ratio of net area to the overall area of the truss.

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Bridge Design For JKR Specification

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2. For the leeward truss of a supestructure with two trusses the drag coefficient shall be taken as rj CD. Value of rj are given in Table 6.7. Spacing ratio

Less than 1 2 3 4 5 6

the mesh becoming filled with rubbish. In these circumstances, the parapet shall be considered as solid. vii. Drag coefficient Co for pier

Value of rj for solidity ratio of 0.1

0.2

0.3

0.4

0.5

1.0 1.0 1.0 1.0 1.0 1.0

0.90 0.90 0.95 0.95 0.95 0.95

0.80 0.80 0.80 0.85 0.85 0.90

0.60 0.65 0.70 0.70 0.75 0.80

0.45 0.50 0.55 0.60 0.65 0.70

Table 6.7 - Shielding factor [Table 7-BD 3 7/88]

The spacing ratio is the distance between centres of trusses divided by the depth of the windward truss. 3. Where a superstructure has more than two trusses, the drag coefficient for the truss adjacent to the windward truss shall be derived as specified in 2. - above. The coefficient for all other trusses shall be taken as equal to this value. b. Superstructures with live load The drag coefficient CD for each truss and for the deck slab shall be as for the superstructure without live load. CD for unshielded parts of the live load shall be taken as 1.45. vi.Drag coefficient CD for parapets and safety fences For the windward parapet or fence, CD shall be taken from Table 8 - BD 37188. Where there are two parapets or fences on a bridge, the value of CD for the leeward element shall be taken as equal to that of the windward element. Where there are more than two parapets or fences the values of CD shall be taken from Table 8 - BD 37/88 for the two elements having the greatest unshielded effect.

The drag coefficient shall be taken from Table 9 - BD 37/88. CD shall be derived for each pier, without reduction for shielding. 6.5.4 Nominal longitudinal wind load, PL [ Cl.5.3.4 - BD 37/88] The nominal longitudinal wind load PL (in N), taken as acting at the centroids of the appropriate areas, shall be the more severe of either: Š the nominal longitudinal wind load on the superstructure, PLS, alone; or Š the sum of the nominal longitudinal wind load on the superstructure, PLS, and the nominal longitudinal wind load on the live load, PLL, derived separately, as specified as appropriate in (1) to (iii) of the followings: (i)All superstructures with solid elevation, PLS = 0.25 q Ai CD Where q : the dynamic pressure head 2 0.613 vc2 the appropriate value of v, for superstructures with or without live load being adopted A, : as defined in 6.5.3 [CL5.3.3 - BD 37/88] for the superstructure alone CD : the drag coefficient for the superstructure as defined in 6.5.3 [Cl.5.3.3 - BD 37/88], but not less than 1.3. (ii) All truss girder superstructures, PLS = 0.5 q A, CD Where

Where parapets have mesh panels, consideration shall be given to the possibility of Cawangan Jalan, Ibu Pejabat JKR, K.L

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: the dynamic pressure head 0.613 vcz , the appropriate value of v, for super structures with or without live load being adopted A l : as defined in 6.5.3 [C1.5.3.3 - BD 37/88] for the superstructure alone CD : the drag coefficient for the superstructure as defined in 6.5.3 [C1.5.3.3 - BD 37/88], CD being adopted where appropriate

Bridge Design For JKR Specification

q

(iii) Live Load on all superstructures PLL = 0.5 q A, CD Where q

: the dynamic pressure head : 0.613 vc2 the appropriate value of v. for superstructures with or without live load being adopted A, : the area of live load derived from the depth dL as given in Table 6.5 and the appropriate horizontal wind loaded length as defined in the note of Table 6.2. CD : 1.45 (iv) Parapets and safety fences (1) With vertical infill members, PL = 0.8 Pt (2) With two or three horizontal rails only, PL = 0.4 Pt (3) With mesh panels, PL = 0.6 Pt Where Pt : the appropriate nominal transverse wind load on the element. (v) Cantilever brackets extending outside main girders or trusses PL is the load derived from a horizontal wind acting at 45° to the longitudinal axis on the area of each bracket not shielded by a fascia girder or adjacent bracket. The drag coefficient CD shall be taken from Table 8 - BD 37/88.

Cawangan Jalan, Ibu Pejabat JKR, K.L

(vi) Piers The load derived from a horizontal wind acting along the longitudinal axis of the bridge shall be taken as PL = q A2 CD Where q : the dynamic pressure head A2 : the solid area in projected elevation normal to the longitudinal wind direction (m2) CD : the drag coefficient, taken from Table 8 - BD 37/88, with values of b and t interchanged. 6.5.5 Nominal vertical wind load, Pv An upward or downward nominal vertical wind load Pv (in N), acting at the centroids of the appropriate areas, for all superstructures shall be derived from Pv = q A3 CL Where q : the dynamic pressure head A; : the area in plan (m2) CL : the lift coefficient as derived from Figure 6.12 for superstructures where the angle of superelevation is less than 1°. Where the angle of superelevation of a superstructure is between 1° and 5°, CL shall be taken as ± 0.75. Where the angle of superelevation of a superstructure exceeds 5°, the value of CL shall be determined by testing. Where inclined wind may affect the structure, CL shall be taken as ± 0.75 for wind inclination up to 5°.The angle of inclination in these circumstances shall be taken as the sum of the angle of inclination of the wind and that of the superelevation of the bridge.

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Bridge Design For JKR Specification Maximum shade air temperature = 35° C

6.6 Temperature [C1.5.4 - BD 37/88] 6.6.1 General Daily and seasonal fluctuations in shade air temperature, solar radiation, re-radiation, etc, cause the following: i. Changes in the effective temperature of a bridge superstructure which, in turn, govern its movement. The effective temperature is a theoretical temperature calculatedby weighting and adding temperature measured at various levels within the superstructure. The weighting is in the ratio of the area of cross section at the various levels to the total area of cross section of the superstructure. Over a period of time there will be a minimum, a maximum, and a range of effective bridge temperature, resulting in loads and/or load effects within the superstructure due to a. restraint of associated expansion or contraction by the form of construction such as portal frame, arch, flexible pier, elastomeric bearings which referred to as temperature restraint; and b. friction at roller or sliding bearings where the form of the structure permits associated expansion and contraction, referred to as frictional bearing restraint. ii. Differences in temperature between the top surface and other levels in the superstructure. These are referred to as temperature differences and they result in loads and/or load effects within the superstructure. Effective bridge temperatures are derived from the isotherms of shade air temperature. 6.6.2 Minimum and maximum shade air temperature

6.6.3 Minimum and maximum effective bridge temperature The minimum and maximum effective bridge temperature for different types of construction shall be derived from the minimum and maximum shade air temperatures. The different types of construction are as shown in Figure 9BD 37/88. 6.6.4 Range of effective bridge temperature In determining load effects due to temperature restraint, the effective bridge temperature at the time the structure is effectively restrained shall be taken as datum in calculating expansion up to the maximum effective bridge temperature and contraction down to the minimum effective bridge temperature. 6.6.5 Temperature Difference [Cf. 5.4.5 - BD 37/88] Effects of temperature differences within the superstructure shall be derived from the data given in Figure 9- BD 37/88. Positive temperature differences occur when conditions are such that solar radiation and other effects cause a gain in heat through the top surface of the superstructure. Conversely, reverse temperature differences occur when conditions are such that heat is lost from the top surface of the bridge deck as a result of reradiation and other effects. Adjustment for thickness of surfacing. Temperature differences are sensitive to the thickness of surfacing, and data given in Figure 9- BD 37/88 assume depths of 40mm for groups 1 and 2 and 100mm for groups 3 and 4. For other depths of surfacing values are given in Appendix C - BD 37,188.

Minimum shade air temperature = 22° C Cawangan Jalan, Ibu Pejabat JKR, K.L

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6.6.6 Coefficient of thermal expansion [C1.5.4.6 - BD 37/88] For the purpose of calculating temperature effects, the values of coefficients of thermal expansion, a, are as follows: Š 12 x 10-6 /°C - for structural steel and for concrete Š 9 x 10-6 /°C - for concrete with limestone aggregate 6.6.7 Nominal values [C1.5.4.7-BD 37/88] i. Nominal range of movement The effective bridge temperature at the time the structure is attached to those parts permitting movement shall be taken as datum and the nominal range of movement shall calculated for expansion up to the maximum effective bridge temperature and for contraction down to the minimum effective bridge temperature.

Bridge Design For JKR Specification displace the elastomer by the amount of expansion or contraction for the appropriate effective bridge temperature range shall be taken as the nominal load The nominal load shall be determined in accordance with 5.14.2.6 of BS 5400: Part 9: Section 9.1: 1983. iii. Nominal load for frictional bearing restraint The nominal load due to frictional- bearing restraint shall be derived from the nominal dead load, the nominal superimposed dead load, using the appropriate coefficient of friction given in tables 2 and 3 of BS 5400: Part 9: Section 9.1 1983. iv.Nominal effects of temperature difference The effects of temperature difference shall be regarded as nominal values. 6.6.8 Design values [C5.4.8 - BD 37/88]

ii. Nominal load for temperature restraint

i. Design range of movement

The load due to temperature restraint of expansion or contraction for the appropriate effective bridge temperature range shall be taken as the nominal load.

Š For ultimate limit state - 1.3 times the appro priate nominal value Š For serviceability limit state -1.0 times the nominal value

Where temperature restraint is accompanied by elastic deformations in flexible piers and elastomeric bearings, the nominal load shall be derived as follows:

For the purpose of this clause, the ultimate limit state shall be regarded as a condition where expansion or contraction beyond the serviceability range up to the ultimate range would cause collapse or substantial damage to main structural members. Where expansion or contraction beyond the serviceability range will not have such consequences, only the serviceability range need be provided for.

a. Flexure of piers For flexible piers pinned at one end and fixed at the other, or fixed at both ends, the load required to displace the pier by the amount of expansion or contraction for the appropriate effective bridge temperature range shall be taken as the nominal load b. Elastomeric bearings For temperature restraint accommodated by shear in an elastomer, the load required to Cawangan Jalan, Ibu Pejabat JKR, K.L

ii. Design load for temperature restraint For Load Combination 3, YfL = 1.30 for U.L.S yn. = 1.00 for S.L.S iii. Design load for frictional bearing restraint For Load Combination 5, Page 75

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ya. = 1.30 for U.L.S yfL = 1.00 for S.L.S Associated vertical design load - The design dead load and design superimposed dead load shall be considered in conjunction with the design load due to frictional bearing restraint. iv.Design effects of temperature difference For Load Combination 3, yo. = 1.00 for U.L.S yfl, = 0.80 for S.L.S

6.7 Effects of Shrinkage and Creep, Residual Stresses, etc. [C1.5.5-BD 37/88] Where it is necessary to take into account the effects of shrinkage or creep in concrete, stresses in steel due to rolling, welding or lack of fit, variations in the accuracy of bearing levels and similar sources of strain arising from the nature of the material or its manufacture or from circumstances associated with fabrication and erection, requirements are specified in the appropriate Parts of BS 5400.

6.8 Differential Settlement [C1.5.6 - BD 37/88] Where differential settlement is likely to affect the structure in whole or in part, the effects of this shall be taken into account. i. Assessment of differential settlement In assessing the amount of differential movement to be provided for, the designer shall take into consideration the extent to which its effect will be observed and remedied before damage ensues. ii. Design load The values of yn. given are based on the assumption that the nominal values of settlement assumed have a 95% probability of not being exceeded during the design life of the structure. The factor of to be applied to the effects of differential settlement, shall be taken

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Bridge Design For JKR Specification for all five load combinations as follows: yfL = 1.20 for U.L.S yn. = 1.00 for S.L.S

6.9 Exceptional Loads [Cd.5.7-BD 37/88] Where other loads not specified in the standard are likely to be encountered, such as the effects of abnormal indivisible live loads, earthquakes, stream flows, these shall be taken into account. The nominal loading to be adopted shall have a value in accordance with the general basis of probability of occurrence. (i)Design loads For abnormal indivisible live loads, yfL shall be taken as specified for HB loading. For other exceptional design loads, yfL shall be assessed in accordance with the general basis of probability of occurrence.

6.10 Earth Pressure on Retaining Structures [C1.5.8 - BD 37/88] 6.10.1 Filling Material [Cl.5.8.1- BD 37/88] i. Nominal Load Where filling material is retained by abutments or other parts of the structure, the loads calculated by soil mechanics principles from the properties of the filling material shall be regarded as nominal loads. The nominal loads initially assumed shall be accurately checked with the properties of the material to be used in construction and, where necessary, adjustments shall be made to reconcile any discrepancies. Consideration shall be given to the possibility that the filling material may become saturated or may be removed in whole or in part from either side of the fill retaining part of the structure.

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ii. Design load For all five design load combinations, yfL shall be taken as follows:

6.11.1 Temporary loads [C1.5.9.1- BD 37/88] (a). Nominal loads.

Vertical loads; yfL = 1.20 for U.L.S yf. = 1.00 for S.L.S Non-vertical loads; yfL = 1.50 for U.L.S yf. = 1.00 for S.L.S

The total weight of all temporary materials, plant and equipment to be used during erection shall be taken into account. This shall be accurately assessed to ensure that the loading is not underestimated. (b). Design loads.

iii. Alternative load factor Where the structure or element under consideration is such that the application of yfL as given in ii. Design load above, for the ultimate limit state causes a less severe total effect than would be the case if yfL , applied to all parts of the filling material, had been taken as 1.0, values of 1.0 shall be adopted. 6.10.2 Live Load Surcharge [C1.5.8.2 -BD 37/88] The effects of live load surcharge shall be taken into consideration. i. Nominal load In the absence of more exact calculations the nominal load due to live load surcharge for suitable material properly consolidated may be assumed to be: (a) for HA loading: 10 kN/m2 (b) for HB loading 45 units: 20 kN/m2 (intermediate values 30 units : 12 kN/m2 by interpolation)

6.11 Erection Loads [C1.5.9 - BD 37/88] For the ultimate limit state, erection loads shall be considered in accordance with (1) to (v) below. For the serviceability limit state, nothing shall be done during erection that will cause damage to the permanent structure or will later its response in service from that considered in design.

Cawangan Jalan, Ibu Pejabat JKR, K.L

For the ultimate limit state for load combinations 2 and 3, yfL shall be taken as 1.15 except as specified in (c). Relieving effect below. For the serviceability limit state for load combinations 2 and 3, yfL shall be taken as 1.00. (c). Relieving effect. Where any temporary materials have a relieving effect, and have not been introduced specially for this purpose, they shall be considered not to be acting. Where, however, they have been so introduced, precaution shall be taken to ensure that they are not inadvertently removed during the period for which they are required. The weight of these materials shall also be accurately assessed to ensure that the loading is not overestimated. This value shall be taken as the design load. 6.11.2 Permanent loads [Cl.5.9.2 - BD 37/88] (a). Nominal loads. All dead and superimposed dead loads affecting the structure at each stage of erection shall be taken into consideration. The effects of the method of erection of permanent material shall be considered and due allowance shall be made for impact loading or shock ' loading.

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(b). Design loads. The design loads due to permanent loads for the serviceability limit state and the ultimate limit state for load combinations 2 and 3 shall be as specified for Dead Load and Superimposed Dead Loads whichever is relevant. 6.11.3 Disposition of permanent and temporary loads [Cl.5.9.3 - BD 37/88] The disposition of all permanent and temporary loads at all stages of erection shall be taken into consideration and due allowance shall be made for possible inaccuracies in their location. Precautions shall be taken to ensure that the assumed disposition is maintained during erection.

6.12 Wind and Temperature Effects [Cl.5.9.4 - BD 37/88] Wind and temperature effects shall be considered in accordance with C1.5.3 - BD 3 7/88 Wind Load and Cl..5. 4 - BD 3 7/88 Temperature, respectively.

Bridge Design For JKR Specification can improve stability as easily as an increase in weight. However, intersections of component parts of the structure are possibly the most time consuming and expensive portions to construct and consequently are best kept to a minimum. Reinforced concrete walls and bases are generally more satisfactory when designed with more than the theoretically economic thickness. Flexural stiffness is increased and steel fixing and concreting are much easier. Followings are some typical types of abutments: Reinforced T Abutment This is the most common form of construction. Often cheaper than mass concrete but relative merits are balanced. Minimum width of base is likely to be achieved with heel larger than toe. However in cutting situation a smaller heel is likely to be economic because of reduced excavation and working space, though sliding resistance is reduced.

CHAPTER 7 - DESIGN OF SUBSTRUCTURE. 7.1 Introduction Substructure of a bridge consists abutments and piers.

7.2 Bridge Abutment and Wing Walls 7.2.1 Type of Bridge Abutments and Wing Walls The stability of a retaining wall is usually calculated in terms of the forces acting on a vertical plane element of unit length. However economies can sometimes be made by considering the full structure as a single three dimensional body. A simple change of shape

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Complicated reinforcement detail make construction slower than semi-mass. For single lift construction walls need to be wide enough for a man to stand between reinforcement to simplify construction and inspection. Bank Seats On Piles Bank seats are placed on piles beside cuttings and on embankments when the ground or fill is not string enough. However settlement of the embankment can subject the piles to downdrag settlement and loads. They are found more convenient if the piles can be placed at the same time as other piles in the contract (usually at start). They can be uneconomic if the piles Page 78

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restrict the construction sequence or require remobilising plant.

Reinforced Earth Abutment Reinforced earth is appropriate for situations with embankments behind: but less likely to be suitable in cuttings or where ties interfere with boundaries and obstructions. The structure has a large tolerance for movement and so is ideal for sites with poor ground near the surface (but if poor stratum is deep then circular slip is not resisted by ties). Differential settlement between abutments and embankment should be smooth. A batter to the front face helps to hide forward movement or facing during construction.

The wall can be built overhand with a minimum working space. Damaged facing units if appropriately design can be replaced during life without affecting stability.

7.3 Design Concept of Bridge Abutment and Wing Walls The design of abutments and wing walls in accordance with BS 5400 is very different to their design to previous practice (CPI10). A Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification major difference is the number of analysis which need to be carried out. Previously, a single analysis covers all aspects - of design but, in accordance with BS 5400, five analyses, each under a different design load, have to be carried out for the following five design aspects. (i). Strength at the ultimate limit state. (ii). Stresses at the serviceability limit state. (iii).Crack widths at the serviceability limit state; but deemed to satisfy rules for bar spacing are appropriate in some situations. (iv).Overturning. BS 5400 requires the least restoring moment due to unfactored nominal loads exceed the greatest overturning moment due to the design loads. (v). Factor of safety against sliding and soil pressures due to unfactored nominal loads in accordance with CP 2004. A further important difference in design procedures occurs when considering the effects of applied deformations described in BS 5400 and in the previous documents. In the previous practice, all design aspects are considered under working load conditions, and thus the effects of applied deformations (creep, shrinkage and temperature) need to be considered for all aspects of design. However, the effects of applied deformations can be ignored under collapse conditions. Thus Part 4 of BS 5400 permits creep, shrinkage and temperature effects to be ignored at the ultimate limit state. The implication of this is that less main reinforcement would be required in an abutment designed to BS 5400 than one designed to the previous documents. Although the effects of applied deformations can be ignored at the ultimate limit state, they have to be considered at the serviceability limit state. The effects of applied deformations thus contribute to the stresses at the serviceability limit state. Since less reinforcement would be present in an abutment designed to BS 5400 than one designed to the previous documents, the stresses at the serviceability limit state would be greater than in the former abutment. Page 79

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However, it is unlikely that they would exceed BS 5400 limiting stresses of 0.8fy and 0.5f, for reinforcement and concrete respectively.

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FLOWCHART - DESIGN OF ABUTMENT

Determine the sizes and dimensions

Determine type, number and arrangement of pile to be used

Calculate all loads

Design

- Dead loads - Superimposed dead loads - Live Loads - Self weight - Other

- Wing Walls - Ballast Walls - Bridge Seat - Corbel

Nominal Loads

Check adequacy of piles;

OK

- Vertical/Axial adequacy - Horizontal adequacy

Loads at ULS

Design Abutment Wall Forces in Pile Cap at ULS

As Cantilever Beam As Reinforced Concrete Wall

Design Pile Cap Short Column

Reinforcement

Check Shear requirements, - Punching - Flexure Shear

Long Column

- Reinforcement - Main - Links

Loads at SLS

Check for SLS requirements: - Stress limitations - Crack width

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7.4

Wing Wall

Wing walls shall be designed as slabs which are loaded by live loads and earth pressure. In this case, slabs shall be cantilever slabs fixed to the wall or two-sides fixed slabs fixed to the wall and footing. Generally, the abutment is provided with wing walls for the purpose of protecting earth at the back of the abutment and such wing walls are fixed to the body of the abutment or its ballast wall in the direction at right angle. There are few shape of wing wall as shown in Figure 10.4. Type (a) and (b) are called as side wall type and type (c) is called as parallel type. The shape and size of wing walls considerably vary depending on site conditions, height of embankment behind the abutment and the slope of embankment. Since wing wall is directly fixed to the body of abutments for holding earth at the side of abutments, it shall be designed in consideration of live loads and earth pressure.

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Bridge Design For JKR Specification

The design of the wing wall shall be based on slab construction and it shall be designed as a two-sides fixed slab for Type (a) and (b) and as cantilever slab for Type (c). But the analysis of two-sides fixed slab is complicated, therefore it may be designed in the following conventional method if L1 and LZ as shown in Figure 10.3 are not so long (i.e. less than 8 metres). The portion of A and D in the Figure shall be designed as cantilever beams supported by a-b and e-f respectively. In this case, the design of the a-b and e-f may be accomplished by evenly distributing over the a-b and e-f portions the fixed end cross sectional force which is obtained by causing earth pressure resultant force acting on A and A portions to act on the cantilever beams. B and C portions also shall be designed as cantilever beams supported by b-c and cd. In this case, b-c and c-d are divided into two sections such as b-b' and b'-c and c-c' and c'-d respectively and each section should be designed with a cross section force applied which is calculated at the most adverse point of each section. In Figure 10.4, section b-b' can be designed by moment Mb per unit length at point b and in the same manner, b'-c by Mb', c-c' by M,' and c'-d can be designed by Md respectively.

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However, when L 1 or L2 exceeds 8 metres, difference is generated between the result of analysis of two-sides fixed slab and that of the conventional method. The conventional method tends to cause an uneconomical design. Consequently, it is desirable that the wing wall be designed as a two-sides fixed slab when the length is over 8 metres. In designing the thickness of wall and the arrangement of reinforcing bars, careful consideration shall be given so that the force is safely and securely transmitted to structures and it is desirable that haunches be provided at joints of walls since they tend to become weak points of the structure. Since the main horizontal reinforcing bars of a wing wall is parallel type and must be anchored to reinforcing bars of secondary (horizontal bar) of the ballast wall, it may become necessary to use additional reinforcing bars in the ballast wall if the thickness of the ballast wall or the horizontal reinforcing bars of the ballast wall is smaller than that of the wing wall.

Bridge Design For JKR Specification

7.5

Ballast Wall

The ballast wall must be designed so that it is safe against the impact of wheel load, wheel load and earth pressure acting on the back of abutment. Moreover, unforeseen external forces such as forward slide of abutment, displacement of beams etc., may act on the ballast wall. Therefore the ballast wall must be sufficiently reinforced.

7.6

Piers (Columns)

7.6.1 Introduction Piers are normally designed as columns or reinforced concrete wall. A reinforced concrete column is a compression

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member whose greater lateral dimension is less than or equal to four times its lesser lateral dimension, and in which the reinforcement is taken into account when considering its strength. A column should be considered as short if the ratio 1,1h in each plane of buckling is less than 12, where le :

the effective height in the plane of buckling under consideration

h

the depth of the cross section in the plane of buckling under consideration

:

A reinforced wall is a vertical load bearing concrete member whose greater lateral dimension is more than four times its lesser lateral dimension, and in which the reinforcement is taken account when considering its strength.

Vehicle Collision Loads on Highway Bridge Supports and Superstructures (Volume 1 Section 3 Part 5 BD 60/94) Vehicle collision loads on supports and superstructures shall be considered for the design of bridges and other highway structures as secondary live loads, as defined in BD 37 (DMRB 1.3), and shall be applied in Load Combination 4. No other live load shall be considered as coexistent. Where bridges over carriageways have supports of which any part is located within 4.5m of the edge of a carriageway, these shall be designed to withstand the vehicle collision loads given in Table 10.3. However, where foot/cycle track bridge ramps and stairs are structurally independent of the main highway spanning structure, their support may be designed to the loads classified in Clause 6.8 of BD 37/88, as shall all foot/cycle track bridge supports with a carriageway clearance equal to or greater than 4.5m. In the case of multi level carriageways, such as those encountered in

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Bridge Design For JKR Specification

motorway, trunk or principal road interchanges, the collision loads are to be considered for each level of carriageway separately. Vehicle collision on abutments need not normally be considered as they are assumed to have sufficient mass to withstand the collision loads for global purposes. Where bridges over carriageway have a headroom clearance less than 5.7metres, the vehicle loads on superstructures shall be considered. Load normal to the carriageway below

Load parallel Point of application to the on bridge support carriageway below

KN

KN

500

1000

250

500

Main load component

Residual load component

At the most severe point between 0.75m and 1.5m above carriageway level At the most severe point between 1 m and 3m above carriageway level

Table 10.1 - Nominal Collision Loads on Supports of Bridges over Highways

Nominal Loads on Supports The nominal loads are given in Table 10.1 together with their direction and height of applications and shall be considered as acting horizontally on bridge supports. Supports shall be capable of resisting the main and residual load components acting simultaneously. Loads normal to the carriageway shall be considered separately from loads parallel to the carriageway. Nominal Loads on Superstructures The nominal loads are given in Table 10.2 together with their direction of application. The load normal to the carriageway shall be considered separately from the load parallel to the carriageway. The load shall be considered to act as point loads on the bridge superstructure in any direction between the horizontal and vertical. The load shall be applied to the bridge soffit, thus precluding a

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downward vertical application. Given that the plane of the soffit may follow a super-elevated or non-planar (curved) form, the load normal to the carriageway may be applicable in either sideways direction. Load normal to the carriageway below

Load parallel to the carriageway below

kN

kN

250

500

Point of application on bridge superstructure

On the soffit in any inclination between the horizontal and the (upward) vertical

General Principles The intention behind the requirements is that the overall structural integrity of the bridge should be maintained following the impact but that local damage to a part of the bridge deck can be accepted. Design Checks - Supports and Superstructures of Bridges Design checks shall be carried out in two stages as described below: Stage 1 - At the moment of impact A check is to be made at ULS only, using the nominal impact loads with partial factors ya. appropriate to Load Combination 4. No other live load is to be included in this check. Local damage is to be ignored. It is assumed that full transfer of the collision forces from the point of impact takes place.

have effected the transfer to the next element(s) in the load-path, but it must be neglected in carrying out the Stage 2 check. Each element in the load-path shall be considered on the same basis. It should be noted that in adequacy at this stage is not a cause for concern, since such inadequacy generally helps to absorb the impact force. In order to prevent the whole structure being bodily displaced by the impact, its bearings or supports shall be designed to be fully adequate to resist the impact loads. Stage 2 - Immediately after the impact Immediately after the event, the bridge has to be able to stand up whilst still carrying traffic which may be crossing. Since the check is one of survival and the likely traffic is of an everyday intensity, it shall be carried out at ULS only using the partial load factors normally appropriate to SLS. Load Combination 1 shall be used. The partial factor ym and yea should take their usual UL S values. HA loading and/or a maximum of 30 units of HB loading shall L.: applied for bridges carrying public highways. For this check, judgement has to be made what local damage might reasonably have occurred and must ignore elements which were assumed or found to be inadequate in Stage 1. If the structure does not satisfy the Stage 2 check, ten Stage 1 will have to be repeated with different assumptions about the adequacy of some elements in the load-path. To justify such amended assumptions, elements may need to be redesigned to ensure their adequacy. Elastomeric Bearings

For the bridge, as in design for all other load cases, it has to determined a likely and reasonable load-path to transfer the impact loads to the bearings, supports and foundations (in the case of superstructures strikes) or to foundations, bearings or other supports (in the case of support strikes). Each structural element in the load-path is to be considered, starting with the element which sustains the immediate impact. If it is assumed or found to be inadequate, it may nevertheless be assumed to Cawangan Jalan, Ibu Pejabat JKR, K.L

For elastomeric bearings, the effects due to vehicle collision loads on supports and on superstructures should only be considered at the serviceability limit state. The yfL to be applied to the nominal loads shall have a value of 1.0.

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Foundations Foundations shall be designed to resist the impact forces transmitted from the collision using BD 30 (DMRB 2.1) and/or BD 32 (DMRB 2.1), as appropriate, with the following qualifications: (i). Only ULS checks are required, both for structural elements and soil-structure interaction. (ii). When checking against sliding of the base and bearing capacity, even for piled foundations, the collision loads shall be reduced by 50% but full loading shall be considered for checking against overturning.

7.7

Pile Caps

Bridge Design For JKR Specification section can be obtained at that section, and the total amount of reinforcement at the section determined from simple bending theory. Such a design method is not correct because a pile cap acts as a deep, rather than a shallow, beam; however, the method has been shown by tests to result in adequate designs. This is probably because most pile caps fail in shear and the method of design of the main reinforcement is, largely, irrelevant. The total amount of reinforcement calculated at a section should be uniformly distributed across the section. Shear The design shear is the algebraic sum of all ultimate vertical loads acting on one side of or outside the periphery of the critical section. The shear strength of pile caps is governed by the more severe of the following two conditions.

Pile caps may be designed either by bending theory (as beams) or by truss analogy

(i)Shear along any vertical section extended across the full width of the cap.

7.7.1 Truss Analogy

(ii) Punching shear around the loaded areas.

The truss analogy assumes a strut and tie system within the cap,- and is in the spirit of - a lower bound method of design. The strut and tie system for a four-pile cap is shown in Figure 10.2. The pile caps are designed by taking the apex of the truss at the centre of the loaded area and the corners of the base of the truss at the intersections of the centre lines of the piles with the tensile reinforcement. It can be seen from Figure 10.2 that, because of the assumed structural action, the reinforcement, calculated from the tie forces, should be concentrated in strips over the piles. However, since it is considered good practice to have some reinforcement throughout the cap, BS 5400 requires 80% of the reinforcement to be concentrated in strips joining the piles and the remainder to be uniformly distributed throughout the cap.

(i). Shear along any vertical section extended across the full width of the cap. BS 5400 requires flexural shear to be checked across the full width of a cap at a section at the face of the column, as shown in Figure 10.3. It should be noted that the critical section is not intended to coincide with the actual failure plane, but is chosen merely because it is convenient for design purposes. The enhancement factor (2dla,,) where d is the effective depth and a,, is the shear span which , in the present context, is taken as the distance between the face of the column and the nearer edge of the piles, viewed in elevation, plus 20% of the pile diameter. (ii) Punching Shear

7.7.2 Bending Theory When applying the bending theory, the pile cap is considered to act as a wide beam in each direction. The total bending moment at any Cawangan Jalan, Ibu Pejabat JKR, K.L

Clarke suggests that punching shear of the column through the pile cap need only be considered if the spacing exceeds four times the pile diameter, which is unlikely; thus BS Page 87

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5400 only requires punching of a pile through the pile cap to be considered. BS 5400 does not state what value of allowable design shear stress should be used with the critical section. In view of this, it would be suggested using value from the Table which is appropriate to the average of the two areas of reinforcement which pass over the pile. This suggestion is not

Cawangan Jalan, Ibu Pejabat JKR, K.L

Bridge Design For JKR Specification based upon considerations of the BS 5400 section of figure (b) but of the section which would actually occur as shown in figure (c). The basic shear stress, obtained from Table should then be enhanced by (2dla,,), where should be taken as the distance from the pile to the critical section (i.e. d/2).

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Bridge Design For JKR Specification design loads which should be considered for a

WORKED EXAMPLES 1. WORKED EXAMPLE NO.1 It is required to calculate the nominal and

Cawangan Jalan, Ibu Pejabat JKR, K.L

highway bridge having the longitudinal and cross sections of Figure 1, zero skew and spans of 25 meter. Design to BD 3 7/88 and to BS 5400.

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