The Design of Modern Steel Bridges - TEDI

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176 The Design of Modern Steel Bridges where E cI c is the flexural rigidity of the transverse stiffener between the main girder webs, E fI f is the flexural rigidity of the stiffened flange per unit width between the main girder webs, B is the span of the transverse stiffener between the main girder webs, L is the spacing of the transverse stiffener, and Y is a buckling coefficient depending on the various dimensions of the stiffened panel between the main girder webs and the cantilever portion. Y is 24 for a stiffened panel between main girder webs without any cantilever overhangs. With a cantilever overhang on one or both sides the value of Y depends on the following two ratios: (1) I cc/I c, where I cc is the second moment of area of the cantilever portion of the transverse stiffener and I c that of the portion between the main girder webs (2) B c/B, where B c is the width of the cantilever and B is the width between the main girder webs. Values of Y for different values of the above ratios are given in Table 6.1; the first set of figures applies to the case of the cantilever on one side only, and the figures in brackets apply to the case of the cantilever on both sides of an intermediate panel (see Fig. 6.7). A continuous edge stiffening member may increase the critical buckling load of the stiffened panel because of the former’s flexural stiffness, but the compressive force in it acting furthest from the support line of the panel also enhances the latter’s buckling tendency. The transition takes place if the radius of gyration of the edge member is about 1.65 times that of the stiffened flange. A more comprehensive expression for the critical buckling load of stiffened flanges outside the limitations stated above is given in Reference [3]. If sa is the applied longitudinal stress on the stiffened flange and Af is its area per unit width, then a safety factor of 3 against elastic critical buckling Table 6.1 Coefficients for overall buckling of stiffened flange with cantilever(s) B c/B I cc/I c 0.2 0.4 0.6 0.8 0.2 22.9 22.9 22.9 22.9 (21.9) (21.9) (21.9) (21.9) 0.4 10.8 13.3 14.3 14.8 (8.6) (10.5) (11.2) (11.5) 0.6 2.7 4.2 5.1 5.6 (2.3) (3.3) (3.9) (4.2) 0.8 0.9 1.5 1.9 2.2 (0.8) (1.2) (1.5) (1.7) Note: first figures apply to stiffened panels with cantilever on one side and figures in brackets apply to stiffened panels with cantilevers on both sides.
Stiffened Compression Flanges of Box and Plate Girders 177 Figure 6.7 Geometry of stiffened compression flange. involving deflection of transverse members will require the following minimum value for the transverse members Minimum Ic ¼ 9 16Y s2 aA2 4 f LB EcEfIf 6.10 Stiffened compression flange without transverse stiffeners Construction of a narrow box girder of moderate size may be considerably simplified if only one or two longitudinal stiffeners are provided on the compression flange, without any other form of stiffening. In such a design the buckling of the compression flange will be completely governed by the orthotropic behaviour of the stiffened flange panel. From Section 6.5 the critical buckling stress is given by scro ¼ p 2 B 2 t þ Asx B Dx f 2 þ Dyf 2 þ 2H where all the notation is as given in that section. If the contribution of H is ignored, the expression for s cro can be reduced to scro ¼ 2p 2 B 2 t þ Asx B Dx f 2 ¼ 2p2EIx l2b0te ð6:16Þ
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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
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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
Page 137 and 138: Rolled Beam and Plate Girder Design
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 and 164: pffiffiffiffiffiffiffiffiffiffiffif
Page 165 and 166: een derived as a condition for trea
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 187: Stiffened Compression Flanges of Bo
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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The Design of Modern Steel Bridges - TEDI

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