The Design of Modern Steel Bridges - TEDI

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18 The Design of Modern Steel Bridges Figure 1.15 George Washington Bridge, New York (1931). Figure 1.16 Golden Gate Bridge, San Francisco (1937).
and supported on 8 ft (2.4 m) deep plate girders rather than a lattice structure. From the opening, very substantial horizontal and vertical movements of the deck in wave forms were noticeable even in moderate wind and light traffic, and earned for the bridge a nickname ‘Galloping Gertie’. Before its construction, tests in a wind tunnel had shown it to be capable of resisting gale forces of up to 120 mile/h (193 km/h). On 7 November 1940, a storm that raged for several hours and reached a speed of 42 mile/h (68 km/h) drove the bridge into an uncontrollable torsional oscillation, culminating in its collapse into the water. After the great success of long-span bridges in the previous 60 years, this disaster shook the very foundations of bridge building. The following official enquiry by three great engineering experts, von Karman, Ammann and Glen Woodruff, blamed no individuals and pointed out no mistakes; it attributed the failure to a lack of proper understanding and knowledge of the whole profession. The deck was too narrow for the span and thus its torsional rigidity was inadequate, and the plate girders not only provided insufficient flexural rigidity, but their bluff elevation caused wind vortices above and underneath the deck even in moderate and steady wind speeds. Figure 1.17 Tamar Suspension Bridge, England (Brunel’s bridge can also be seen). Figure 1.18 Mackinac Bridge, Michigan (1957). Types and History of Steel Bridges 19
Page 1: The Design of Modern Steel Bridges
Page 5 and 6: The Design of Modern Steel Bridges
Page 7 and 8: Contents Preface vii Acknowledgemen
Page 9 and 10: Preface Bridges are great symbols o
Page 11: Acknowledgements The figures in Cha
Page 14 and 15: 2 The Design of Modern Steel Bridge
Page 22 and 23: 10 The Design of Modern Steel Bridg
Page 58 and 59: Table 2.1 Properties of some commer
Page 63 and 64: Chapter 3 Loads on Bridges 3.1 Dead
Page 65 and 66: 3.3 Design live loads in different
Page 67 and 68: interstate highways are designed fo
Page 69 and 70: a coefficient that depends on the n
Page 71 and 72: Loads on Bridges 59 In Germany, a n
Page 73 and 74: Table 3.6 Typical values of U and P
Page 75 and 76: 3.5 Longitudinal forces on bridges
Page 77 and 78: wind loading on the traffic. An upl
Page 79 and 80: where r is the air density ¼ 1.226
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Loads on Bridges 69 minimum and max
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3.8 Other loads on bridges There ar
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References Loads on Bridges 73 wher
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Chapter 4 Aims of Design 4.1 Limit
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critical components of the structur
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But this is an attempt to achieve u
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If the basic variables R and S are
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educed variables defined by oi ¼ x
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will have a probability of failure
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Aims of Design 87 g m ¼ g m1 g m2
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Table 4.2 Failure probabilities of
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Chapter 5 Rolled Beam and Plate Gir
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as possible. But deep and thin webs
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eam, with an effective area equal t
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and stresses caused by lateral defl
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Figure 5.3 Beam cross-section. In t
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Rolled Beam and Plate Girder Design
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Table 5.2 Effective length factors
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stress is equal to p 2 E/(Le/r) 2 )
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equation (5.16) has been adopted fo
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The strain energy of the elastic re
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Figure 5.6 Buckling of plates in co
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Figure 5.8 Buckling of plate under
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techniques. It may be noted that th
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5.4.3 Effect of residual stresses R
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Aw ¼ 40 mm 2 , allowing for a smal
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Basler and Thurlimann were the firs
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Ostapenko/Chern gave the following
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where m ¼ Mp b 2 twsyw ty ¼ syw p
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the case of equal flanges, the tota
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emains flat until an elastic critic
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longitudinal compression is given b
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where Peq ¼ s1tB PE Ps Pcro Peq1
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Figure 5.27 Tension-field forces in
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5.5.6 Design of longitudinal web st
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when Le is the effective length for
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pffiffiffiffiffiffiffiffiffiffiffif
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een derived as a condition for trea
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For interaction of various stress c
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must be at least i.e. 1 IsxbB 4 2 a
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Chapter 6 Stiffened Compression Fla
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Stiffened Compression Flanges of Bo
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cross-section in which the secant s
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longitudinal compression of the lon
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webs of main girders is denoted by
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wherefrom Ms ¼ 2 3 PE P The net be
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Chapter 7 Cable-stayed Bridges 7.1
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Cable-stayed Bridges 185 cables con
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The following is a list of cable-st
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(a) Fan system (b) Harp system (c)
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7.3.2 Ropes causing lateral compres
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The spiral winding of wires around
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polyethylene or even steel tube. Or
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See Fig. 7.7. Imagine a cable-stay
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It may be noted that: Et is higher
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Reference Cable-stayed Bridges 201
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204 The Design of Modern Steel Brid
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206 The Design of Modern Steel Brid
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