Design And Development Of Overhead Monorail Structure For Material Handling

Design and Development of Overhead Monorail Structure for Material Handling Shashi Sagar1, Ronak R Patel 2, Shashank P Joshi3 1 Assistant professor,SOCET, Ahmedabad , Gujarat,India 2 Assistant professor, 3Associate professor, Birla Vishvakarma Mahavidyalaya, Anand, Gujarat, India Abstract—Overhead Monorail crane structure is generally used to handle medium and large sized object in manufacturing or processing industry. The major challenges in design of overhead monorail structures are, design of curved runway beam and the effect of moving loads. Even though, every structure is designed on the criterion of strength and rigidity, the loading characteristics of application make every design unique. In the present paper, design approach for an overhead monorail structure to transport 6 ton on straight and curved path is discussed. The design is required for material handling in shot blasting. The aim is to build a basic approach based on structural strength and rigidity using appropriate standards i.e. CMAA 74 and IS standard with all the possible loading conditions like trolley loads, loading due to movement of trolley. Bottom flange bending, local capacity check, fatigue check and deflection check is carried out for monorail runway beam design and determining span length. The design of straight and curved runway beam is done with simply supported conditions to avoid failure of entire system. Additional lateral loads and axial loads due to motion of trolley are considered. Bending stress due to both in-plane and on-plane bending moment along with torsion are estimated for interaction ratio of monorail beam. For curved monorail runway beam, the torsional effect, warping effect and lateral torsional buckling is taken in consider since it affects the strength and rigidity of curved beam significantly. The validation of design calculation is done by software STAAD Pro V8i. This paper presents complete approach of monorail beam design procedure including its supporting structures.

condition and design criterion are similar to that for any structural application. The present work is an attempt to design an overhead monorail crane structure for lifting and transporting the maximum load of 6 ton through the given path as shown in fig. 1 at a speed of 1m/min for shot blasting purpose. The design must comply the appropriate standards, at the same time the design must ensure the strength and rigidity and must withstand the application specific design criteria.

Keywords— Monorail structure, Curved runway beam, STAAD Pro, Bottom flange bending, CMAA 74, Warping stress Fig 1. Schematic diagram of monorail system

I.

INTRODUCTION

Overhead monorail cranes are used for lifting and transporting objects to the destination point or station for intended application e.g. shot blasting and return from the station to the unloading point. Each overhead monorail crane is designed and. manufactured according to these requirements i.e. the load, path of travel, number of trolleys, space availability, speed of trolley and frequency etc. Hence, every monorail crane design is a customized design; however general loading

The design specifications for monorail crane runway beam are according to CMAA 74: Specifications for top running and under running single girder electric overhead crane under running trolley hoists. The design of structural support must follow IS 800: Code for general construction in steel. II. DESIGN APPROACH For designing, following steps has been followed: • Classification of monorail system according to CMAA 74. • Selection of trolley based on maximum load to be conveyed.

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• Design of runway beam a) Selection of standard I beam for runway beam from IS 808 suitable to trolley wheel. b) Compute the different loads like self-weight of beam, trolley load and wheel load with load factors according to CMAA 74. The lateral load factor and axial load factor is selected from IS 875 part 2. c) Design of monorail runway beam for maximum design loads and lateral loads. d) Find the appropriate support positions (span length) for runway beam. • Design of supporting structure a) Compute the maximum hanger load (MHL) for designing the supporting beam. b) Design the supporting beam and column. • Develop the layout for monorail system. III. RUNWAY BEAM DESIGN In order to determine the rated capacity, the capacity of monorail section is first calculated using three different criteria, each of which imposes a maximum load limit, and the minimum of the following three calculated values. 1. The maximum allowable tensile stress 2. The maximum allowable compression stress 3. The maximum allowable deflection In practice, the actual load is usually suspended from one or more monorail trolleys and is therefore transmitted to the supporting monorail, at two or more points. Therefore, it is necessary to convert the actual distributed load into an equivalent center load, ECL [1]. A. Determination of Equivalent center load The first step in determining the ECL is to calculate the total design load, P imposed on monorail by the loaded trolley. Total design load is determined with load factors according to CMAA74 .Calculation of ECL is grouped into three categories. a) Equal wheel loading , Four wheel Trolley b) Equal wheel loading , Eight wheel Trolley c) Unequal wheel loading, general solution Here, first two conditions are discussed. Case a: Equal wheel loading, Four wheels Trolley

In fig. 2 the four wheel trolley is shown in the position that will produce the maximum bending moment in the runway beam. P = Maximum design load L= Rail span between supports A = wheel base of trolley To determine the ECL, the design load P is multiplied by the coefficient C, so that …….(1) In which C = coefficient due to load distribution. When the wheelbase is relatively short with respect to the span, i.e. a ≤ L/4, then the approximate value of C may be calculated by the use of a very simple equation. Although the result is an approximation, the error is on the order of 2% or less, and because of its simplicity the following equation is widely used within the monorail industry[1]. ……(2) When greater accuracy is necessary, or desired, then the exact value of C may be determined by the following: …….(3) The above equation applies for all values of „a’ up to and including a = 0.586 L. For values of a greater than 0.586 L, C = 0.50. Case b: Equal wheel loading, Eight wheels Trolley: In fig. 3 the eight wheel trolley is shown in the position that will produce the bending moment in runway beam.

Fig 3. Maximum bending moment with eight wheel trolley

P = maximum design load (equally distributed) L = rail span between supports a = principal wheel base of trolley t = wheel base of auxiliary four wheel trolleys As in case 1, C may be calculated by use of, When a ≤ L/4, and t ≤ a/4. After which

Fig 2. Maximum bending moments with four wheel trolley

This takes into account the fact that when t ≤ a/4, the influence of the spread of auxiliary trolley wheels is minimal, and for ease of calculation each pair of auxiliary trolley loads, may be assumed to be acting at a single point.

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However, when t ≥ a/4, or where greater accuracy is required, the exact value of C may be determined by the equation: .(4) When a is greater than 0.586 L, the auxiliary four wheel trolley is next positioned as to produce the maximum bending moment in the span being analyzed, as in case 1 and the calculation may then proceed in the same manner as in the case of a four wheel trolley.

Comparative bending moment diagram under both cases shown in fig. 5, In second case for design, if one span failed by some reason it may cause failure of full system. So we prefer to design by considering the single span as simply supported to avoid the collapse of structure.

B. Calculation of Hanger Loads After having determined the ECL, a rail of the proper depth and weight may be selected to suit the span and specified deflection limits. It then becomes necessary to calculate the maximum hanger loads will, in turn, provide the loading data necessary for designing or checking the design of, the overhead supporting structure. The term Maximum Hanger Load (MHL) is defined as the maximum reaction occurring at the hanger being analyzed due to the maximum live load P imposed by the trolley or end truck, plus the weight of runway beam.

Fig 5. Comparative bending moment diagram IV.

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Fig 4: Maximum hanger load, eight - wheel trolley

In order to determine the MHL, the trolley is first centered under the hanger being analyzed (H2) as shown in fig. 4. The load at hanger H2, or the MHL, may be determined by the use of simple equation: MHL= KP + rail weight ……..(5) Where: P= total design load K= distribution factor ……..(6) The factor K is applicable to either four wheel or eight wheel trolleys so long as all of the stipulated conditions have been met [1]. C. Support Conditions The two ends of the runway beam are assumed to be simply supported, in the sense that the flexural displacements and twisting rotation of the beam are restrained at the supports. Consider two cases of support, 1. Single span is designed considering simply supported. 2. Simply supported continuous beam

SUMMARY OF DESIGN CALCULATIONS

The desired overhead monorail system is classified as Class B according to CMAA 74 [4]. Two trolleys with four wheels each are selected with capacity of 3 ton from the company catalogue. ISMB beam is selected for runway beam in accordance with trolley Loads are calculated with different load factors [4,6] summarized below: Self-weight of runway beam (W): 402.5 N/m Maximum load of each trolley on runway beam, Ptrolley= 34856.103 N Axial load, Paxial = 1742.80 N (Axial load factor = 0.05) Lateral load, Plateral = 3485.60 N (Lateral load factor = 0.1) Wheel load, Pwheel = 8714.026 N

A. Results of Straight Runway Beam Straight runway beam is checked for stresses, deflection and local bending of bottom flange according to CMAA 74. The summary of results is shown in table 1. B. Results of Curved Runway Beam While designing the support positions for curved runway beam, we have to consider both torsional and bending effect. The torsional effect causes additional bending stress and warping stress.so, the effect of torsional moment is considered by evaluating the value of warping stress and minor axis bending stress due to torsion. To find the angle of curvature for curved beam is trial and error process. The curved beam is analyzed for 45˚, 36˚ and 30˚. The vertical load is same as calculated in case of design of straight runway beam. The centrifugal force is added to the lateral load. Centrifugal force = 0.28 N

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Total lateral load = Plat + 0.28 = 3485.88 N The summary of results is shown in table 2. TABLE 1 SUMMARY OF STRAIGHT RUNWAY BEAM DESIGN

The supporting structure is designed with three column support and results are analyzed with help of STAAD Pro and checked with IS 800The modeled frame of supporting structure is shown in fig. 7 .

Beam ISMB 250 Span Length 3 meter Permissible Tensile stress 150 MPa Permissible Compressive stress 165 MPa Major Axis Actual bending stress (T) Minor Axis

61.85MPa 62.25 MPa At point At point 0 At point 1 2 Local bending stress of bottom flange (C) 145.57 162.77 82.2 MPa MPa MPa Support reactions (MHL) 41.65 kN Deflection 1.94 mm < (L/450) Interaction Ratio 0.833 < 1

Fig 7. Modelled frame of supporting structure

The results from STAAD Pro is summarized below:

TABLE 2: SUMMARY OF CURVED RUNWAY BEAM DESIGN

Beam Angle of Curvature Span length Actual bending stress (T) Warping stress Bending stress due to torsion Shear stress Interaction ratio Local bending stress of bottom flange (C) Deflection

ISMB 250 30˚ 1.57 meter Major 16.005MPa Axis Minor 26.174 MPa Axis 81.753 <150 MPa 

11.74 MPa 66.5 MPa < 93.33 MPa 0.90 < 1 At point At point 0 1 79.01 95.8 MPa MPa 0.34 mm < (L/450)

V. CONCLUSIONS

At point 2 27.28 MPa

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From the calculated results, it is concluded that tapered flange is better than parallel flange in case of designing runway beam. For curved beam design warping is having significant effect so the torsional effect must be considered in design.

C. Results of supporting structure The support structure is designed for withstand maximum load.Considering three column supports for supporting beam with 2 m clearance from runway beam and supporting beam connection. At a moment, only one side of system is in loading condition as shown in fig. 6. .

Fig 8. General layout of full monorail structure

 Fig 6. Schematic diagram of supporting beam with 3 column support

Local bending of bottom flange because of wheel load should be considered in design of runway beam.

International Conference on “Research and Innovations in Science, Engineering & Technology” ICRISET-2017

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For making safe our design, bottom flange bending is checked which is iterative process. We checked for span length 3.5 m, 3.4 m, 3.3 m, 3.2 m, 3.1 m and 3.0 m and found to be safe with 3.0 m span length. Deciding the support positions for curved beam is trial and error process. So start the curved beam design with equivalent angle of curvature of straight runway beam and determine optimum angle of curvature for support position. The developed layout of structure is shown in fig. 8 ACKNOWLEDGEMENT

I wish to express my sincere appreciation to my project supervisor for their guidance, advices and motivation. I am also thankful to Nesco Ltd. for providing me this opportunity. REFERENCES [1] Raymond a. kulweic, Material Handling Handbook, 2nd Edition John Wiley & Sons Publication [2] Warren C. Young, Richard G. Budynas, Roark‟s Formulas for Stress and Strain ,Seventh Edition McGraw-Hill [3]

Tomas H Orihuela,"Design of Monorail Systems", Integrity Crane

System. [4] Crane Manufacturers Association of America, Inc. (CMAA) Specification No. 74, Revised 2000, Specifications for Top Running and Under Running Single Girder Electric Overhead Cranes Utilizing Under Running Trolley Hoists. [5] IS 800:2007. General construction in. Steel - code of practice. (Third revision). [6] IS 875 part 2 Code of practice for design loads. (Second revision). [7] IS 808 Dimensions for hot rolled steel beam, column, channel and angle sections. (Third revision). .

International Conference on “Research and Innovations in Science, Engineering & Technology” ICRISET-2017