Transcript Chapter 12

Chapter 12
Maximum Deflection in Bridges
The elastic deflections of girders due to L.L. (without dynamic
effect) shouldn’t exceed:Category
Max allowable
deflection
Railway bridges
L/800
Roadway bridges
L/600
Structural buildings
L/300
Crane track girders
L/800
To cancel the deflection due to dead load a cumber is done during
the construction of the beams or trusses, where the structure will
be have the required shape after erection.
In case of suspension bridges the cumber is done by adding both
the deflection due to D.L. and L.L. into consideration.
The minimum sections to be used in structural steel works shall
be as follows:-
Section
Equal angles
Railway
bridges
Roadway
bridges
Structural
buildings
75758
65657
45455
75508
65507
45305
S.I.B.
No20
No16
No12
Channels
No16
No12
No8
Plates
8mm
8mm
5mm
Gusset plates for main
truss
12mm
10mm
unequal angles
8mm