The Design of Modern Steel Bridges - TEDI

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56 The Design of Modern Steel Bridges The loading on the principal lane is multiplied by an impact factor k varying from 1.0 to 1.4 and given by k ¼ 1.4 0.008L, but not less than 1, where L is the span length of the member in metres. In France[7], bridges are classified according to the carriageway widths: class I – bridge with carriageway width equal to or greater than 7 m class II – bridge with carriageway width between 5.5 and 7 m class III – bridge with carriageway width equal to or less than 5.5 m. The carriageway width is divided into an integer number of traffic lanes of width not less than 3 m, except that carriageways with widths between 5 and 6 m are considered to have two lanes. Two different and independent types of loading are considered – a uniformly distributed load A and a vehicle or axle load B. A is given by A ¼ 2:3 þ 360 L þ 12 kN=m2 where L is the loaded length in metres. A is multiplied by coefficient a 1, which depends on the bridge class and number of lanes to be loaded, as shown in Table 3.4. There is another multiplying factor a 2 ¼ V o/V, where V is the width of the lane being considered and Vo ¼ 3.5 m for class I, 3.0 m for class II and 2.75 m for class III. The load (a 1 a 2 A) is placed uniformly over the total widths of the traffic lanes considered. The vehicle or axle load B for each bridge member consists of three independent loading systems: (1) B c consists of two vehicles of 300 kN on each lane, with axle spacings as shown in Fig. 3.2. The value of the vehicle load is multiplied by Table 3.4 Coefficients a1 Bridge class Number of loaded lanes 1 2 3 4 5 I 1 1 0.9 0.75 0.7 II 1 0.9 – – – III 0.9 0.8 – – – Figure 3.2 Axle loading for French loading.
a coefficient that depends on the number of loaded lanes and bridge class shown in Table 3.5. The possibility of the vehicles in two adjacent lanes being very close to each other is allowed for by considering the disposition shown in Fig. 3.3. (2) B r consists of an isolated wheel load of 100 kN with contact area 0.3 m along the direction of travel and 0.6 m across. (3) B t consists of a pair of two axles, each 160 kN, on each lane. The spacing between the two axles is 1.35 m and the transverse distance between the wheels is 2.0 m; the possibility of the axles in adjacent lanes being very close to each other is allowed for by taking the minimum space between the wheels of the two axles as 1.0 m. This loading is multiplied by 0.9 for bridge class II and is not considered for bridge class III. Certain classified routes are designated for the passage of heavy military vehicles weighing up to 1100 kN or exceptional heavy transport represented by two carriers each weighing up to 2000 kN. The impact factor is already included in the loading system A; for the loading system B, the impact factor K is given by K ¼ 1 þ 0:4 1 þ 0:2L þ 0:6 1 þ 4P=S where P is the permanent load, S is the live load B, and L the length of bridge member in metres. A study group set up by the Organisation of Economic Co-operation and Development (OECD) has produced[1] a comparative analysis of the bridge loading standards in the member countries, i.e. the bridge design loading in Belgium, Finland, France, Germany, Holland, Italy, Japan, Norway and Sweden, Spain, the UK and the USA are compared. In some of these countries Table 3.5 Coefficients multiplying B Bridge class Number of loaded lanes 1 2 3 4 5 I 1.20 1.20 0.95 0.80 0.7 II 1.0 1.0 – – – III 1.0 0.8 – – – Figure 3.3 Lateral vehicle disposition for French loading. Loads on Bridges 57
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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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4 The Design of Modern Steel Bridge
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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: interstate highways are designed fo
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
Page 81 and 82: Loads on Bridges 69 minimum and max
Page 83 and 84: 3.8 Other loads on bridges There ar
Page 85 and 86: References Loads on Bridges 73 wher
Page 87 and 88: Chapter 4 Aims of Design 4.1 Limit
Page 89 and 90: critical components of the structur
Page 91 and 92: But this is an attempt to achieve u
Page 93 and 94: If the basic variables R and S are
Page 95 and 96: educed variables defined by oi ¼ x
Page 97 and 98: will have a probability of failure
Page 99 and 100: Aims of Design 87 g m ¼ g m1 g m2
Page 101 and 102: Table 4.2 Failure probabilities of
Page 103 and 104: Chapter 5 Rolled Beam and Plate Gir
Page 105 and 106: as possible. But deep and thin webs
Page 107 and 108: eam, with an effective area equal t
Page 109 and 110: and stresses caused by lateral defl
Page 111 and 112: 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 )
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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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Rolled Beam and Plate Girder Design
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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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The Design of Modern Steel Bridges - TEDI

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