The Design of Modern Steel Bridges - TEDI

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152 The Design of Modern Steel Bridges or syfBT 2 f syb 2 t 1:25 5 p2 s2 sy For S 4 1.0, s2 is zero and hence any web panel adjacent to a flange and with slenderness ratio S 4 1.0 may be taken as restrained irrespective of the size of the girder flange. For web panels with S 5 3.6, s2 ¼ 0.5 sy, and hence such a panel adjacent to a flange can be considered restrained only if the following condition is satisfied for the size of the flange syfBT 2 f syb 2 t 50:0625 s 2 yf s 2 yf s 2 yf s 2 yf s2 f s2 f ! ! ð5:49Þ For a web panel adjacent to a flange and with slenderness ratio 1.0 < S < 3.6, the flange size has to satisfy the following condition for the panel to be considered restrained i.e. 5.7.2 Plates under shear syfBT 2 f syb 2 t 1:25 5 0:192ðS 1Þ p2 5 0:024ðS 1Þ s 2 yf s 2 yf s 2 yf s2 f s 2 yf ! s2 f ! ð5:50Þ In Section 5.4.5 the tension-field strength of a plate subjected to shear was shown to depend upon a flange stiffness parameter m given by m ¼ Mp b 2 tsy This parameter is one-quarter of the ratio of the plastic moduli of the flange plate and the web plate about their respective horizontal centroidal axes, which has been used in the section above for determining the flange stiffness required to achieve restrained plate capacity under compressive applied loading. The minimum values of m required to achieve in the tension field mechanism the levels of shear capacities represented by the restrained plate capacities in shear may be obtained from the expression for tension field strength for different aspect ratios of the plate. These minimum values should, however, be increased by a safety margin, since the tension field mechanism is attained with deformations in the plate, and in the flange member, of a much larger magnitude than is associated with the ultimate strength of orthogonally stiffened plates. By this method, the following stiffness requirement for the flange member has
een derived as a condition for treating the web panels adjacent to the flange to be restrained to remain straight under in-plane shear loading syfBT 2 f syb 2 t 5 0:075ðfÞ1:6 l l 200 l 0:3 , for l > l ð5:51Þ when l ¼ b rffiffiffiffiffiffiffi sy t 355 l ¼ 66 þ 28 f 2 f ¼ aspect ratio L b (All other notation as in preceding sections.) For l 4 l web panels may be deemed to be restrained, irrespective of the flexural stiffness of the flange. 5.8 Design example of a stiffened girder web Rolled Beam and Plate Girder Design 153 Web plate – 10 mm thick, grade 50 steel with sy ¼ 355 N/mm 2 . Applied longitudinal stresses due to factored dead and live loads are shown below. Applied shear stress ¼ 60 N/mm 2 . Further partial safety factors of gf3 ¼ 1.1 and g m ¼ 1.05 are to be allowed for. Figure 5.29 Details of a design example of a girder web.
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The Design of Modern Steel Bridges
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The Design of Modern Steel Bridges
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Contents Preface vii Acknowledgemen
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Preface Bridges are great symbols o
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Acknowledgements The figures in Cha
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2 The Design of Modern Steel Bridge
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10 The Design of Modern Steel Bridg
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Table 2.1 Properties of some commer
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Chapter 3 Loads on Bridges 3.1 Dead
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3.3 Design live loads in different
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interstate highways are designed fo
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a coefficient that depends on the n
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Loads on Bridges 59 In Germany, a n
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Table 3.6 Typical values of U and P
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3.5 Longitudinal forces on bridges
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wind loading on the traffic. An upl
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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
Page 113 and 114: Rolled Beam and Plate Girder Design
Page 115 and 116: Table 5.2 Effective length factors
Page 117 and 118: stress is equal to p 2 E/(Le/r) 2 )
Page 119 and 120: equation (5.16) has been adopted fo
Page 121 and 122: The strain energy of the elastic re
Page 123 and 124: Figure 5.6 Buckling of plates in co
Page 125 and 126: Figure 5.8 Buckling of plate under
Page 127 and 128: techniques. It may be noted that th
Page 133 and 134: 5.4.3 Effect of residual stresses R
Page 135 and 136: Aw ¼ 40 mm 2 , allowing for a smal
Page 141 and 142: Basler and Thurlimann were the firs
Page 143 and 144: Ostapenko/Chern gave the following
Page 145 and 146: where m ¼ Mp b 2 twsyw ty ¼ syw p
Page 147 and 148: the case of equal flanges, the tota
Page 149 and 150: emains flat until an elastic critic
Page 153 and 154: longitudinal compression is given b
Page 155 and 156: where Peq ¼ s1tB PE Ps Pcro Peq1
Page 157 and 158: Figure 5.27 Tension-field forces in
Page 159 and 160: 5.5.6 Design of longitudinal web st
Page 161 and 162: when Le is the effective length for
Page 163: pffiffiffiffiffiffiffiffiffiffiffif
Page 167 and 168: For interaction of various stress c
Page 169 and 170: must be at least i.e. 1 IsxbB 4 2 a
Page 171 and 172: Chapter 6 Stiffened Compression Fla
Page 173 and 174: Stiffened Compression Flanges of Bo
Page 175 and 176: cross-section in which the secant s
Page 177 and 178: longitudinal compression of the lon
Page 179 and 180: webs of main girders is denoted by
Page 183 and 184: wherefrom Ms ¼ 2 3 PE P The net be
Page 195 and 196: Chapter 7 Cable-stayed Bridges 7.1
Page 197 and 198: Cable-stayed Bridges 185 cables con
Page 199 and 200: The following is a list of cable-st
Page 201 and 202: (a) Fan system (b) Harp system (c)
Page 203 and 204: 7.3.2 Ropes causing lateral compres
Page 205 and 206: The spiral winding of wires around
Page 207 and 208: polyethylene or even steel tube. Or
Page 209 and 210: See Fig. 7.7. Imagine a cable-stay
Page 211 and 212: It may be noted that: Et is higher
Page 213: Reference Cable-stayed Bridges 201
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204 The Design of Modern Steel Brid
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