Ce 313-lecture-2(concepts In Structural Steel Design )

‫بسم هللا الرحمن الرحيم‬

STEEL STRUCTURES (I) (CE 313) 1

LECTURE #2

Concepts in Structural Steel Design By

CE 313 STEEL STRUCTURES (I)

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STRUCTURAL DESIGN

Introduction 2

Structural design may be defined as a mixture of art and science, combining the experienced engineer’s intuitive feeling for the behavior of a structure with a sound knowledge of principles of statics, dynamics, strength of materials and structural analysis, produce a safe economical structure which will serve its intended purpose. At the same time it is necessary to be sensitive to preserve environment and natural materials in structural design. So structural design should be safe, economic, aesthetic and sustainable.

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Design concept & rationale

Introduction

ensure strength, stability and stiffness 3

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Design concept & rationale

Introduction 4

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Type of Structural Steel Sections 5

Steel Structural Sections

CE 313 STEEL STRUCTURES (I)

Hot-Rolled Sections. • Cold Formed Sections. • Built-Up Sections. •

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Type of Structural Steel Sections 6

•

Hot-Rolled Sections.

C S W (a) Wide-flange (b) American (c) American Standard Standard Shape Channel Beam

(h) Bars

(i) Plates

CE 313 STEEL STRUCTURES (I)

L (d) Angle

WT or ST (e) Structural Tee

(f) Pipe Section

(g) Structural Tubing

a – Wide-flange : W 18  97 b – Standard (I) : S 12  35 c – Channel : C 9  20 d – Angles : L 64½ e – Structural Tee : WT, MT or ST e.g. ST 8  76 f & g – Hollow Structural Sections HSS : 9 or 8  8 ALGHRAFY 2016

Type of Structural Steel Sections 7

• Cold Formed Sections

(a) Channels

(d) Angles CE 313 STEEL STRUCTURES (I)

(b) Zees

(c) I-shaped double channels

(e) Hat sections ALGHRAFY 2016

Type of Structural Steel Sections 8

• Built-Up Sections. Built-up (W) shapes.

Built-up (C) Channels.

Built-up (L) Angles.

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Type of Structural Steel Sections 9

• Tension Members.

(a) Round and rectangular (b) Cables composed bars, including eye bars of many small wires. and upset bars.

(c) Single and double angles.

Perforated plates

(d) Rolled W – and S – sections. CE 313 STEEL STRUCTURES (I)

(e) Structural tee.

(f) Build-up box sections. ALGHRAFY 2016

Type of Structural Steel Sections 10

• Compression Members.

(a) Rolled W-and S- (b) Double sections. angles.

(c) Structural (d) Structural tee. tubing

(e) Pipe section

(f) Built-up section CE 313 STEEL STRUCTURES (I)

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Type of Structural Steel Sections 11

• Bending Members.

(a) Rolled W-and other I-shaped sections.

(d) Angle

(b) Build-up Sections.

(e) Channel

CE 313 STEEL STRUCTURES (I)

(c) open web joist.

(f) Built-up members

(g) Composite steel-Concrete ALGHRAFY 2016

Tables of Structural Shapes 12

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Tables of Structural Shapes 13

CE 313 STEEL STRUCTURES (I)

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Tables of Structural Shapes 14

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Tables of Structural Shapes 15

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Tables of Structural Shapes 16

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LOADS 17 Dead Loads: Also known as gravity loads, includes the weight of the structure and all fixed and permanent attachments. Live Loads: Also belong to gravity loads, but their intensity and location may vary (non- permanent loads). Highways / Rail Live Loads: AASHTO, AREA Impact Loads: Associated with Live Loads. Snow Load 20 to 40 psf (  1000 to 2000 Pa )

Thermal Loads: For Indeterminate Structures. 9 – Other Loads: e.g. - Rain Loads -Ponding-Hydrostatic Loads - Blast Loads.

Wind Loads: Exerts pressure or suction on the exterior surfaces and it has a transient nature.

Earthquake Load: Latitude Load on structure.

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Philosophies of Design: 18

 Adequate safety no matter what design philosophy is used.  Provision must be made for both overload and understrength.  The fundamental requirement is:

Required strength ≤ Available strength A. Working Stress Design (Allowable Stress Design), widely known as (ASD) – used for over 100 years. Maximum applied stress ≤ Allowable stress Required strength ≤ Allowable strength Allowable strength = Nominal strength / Safety factor A. Limited States Design (Load & Resistance Factor Design), also known as (LRFD) – first introduced in 1986. Load factors are applied to service loads and theoretical strength of the member is reduced by a resistance factor. Σ(Loads x Load factors) ≤ Resistance x Resistance factor CE 313 STEEL STRUCTURES (I)

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Safety factors and load combinations for ASD 19

Safety factors Ra ≤ Rn/ Ω=Rd

Ra= Required strength Rn= Nominal strength (Calculated theoretical strength with no safety factors or resistance factors.) Ω = Safety factor (>1)

Rd= Rn/ Ω = Allowable strength Yielding, flexure or buckling Ω=1.67 Rupture Ω=2.00 Fillet and Weld Ω=2.00

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Safety factors and load combinations for ASD 20

load combinations D D+L D+(Lr or S or R) D+0.75(L)+0.75(Lr or S or R) D+(0.6Wor0.7E) D+0.75(0.6W)+0.75L+0.75(Lr or S or R) D+0.75(0.7E)+0.75L+0.75(S) 0.6D±(0.6W or 0.7E) D=Dead load E=Earthquake load L=Live load Lr=Roof live load R=Rain load S=Snow load W=Wind load CE 313 STEEL STRUCTURES (I)

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Safety factors and load combinations for LRFD 21

Safety factors

ΣγiQi ≤ ΦRn

Qi = A load effect γi =A load factor Rn =Nominal resistance or strength Φ= Resistance factor (<1) ΦRn=Design strength Ru≤ ΦRn Ru=Required strength

1.4D 1.2D+1.6L+0.5 (Lr or S or R) 1.2D+1.6 (Lr or S or R)+(0.5L or0.5W) 1.2D+1.0W+0.5L+0.5(Lr or S or R) 1.2D±1.0E+0.5L+0.2S 0.9D±(1.0W or 1.0E) CE 313 STEEL STRUCTURES (I)

In generalΩ= Φ/ 1.5

D=Dead load E=Earthquake load L=Live load Lr=Roof live load R=Rain load S=Snow load W=Wind load ALGHRAFY 2016

Type of Steel Used 22

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Thank You 23

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2016