Allowable stress and deflection on multiple-span supports
Allowable stress and deflection on multiple-span supports
(OP)
Does anyone knows the formula for allowable stress and deflection of a three or more span continous beam loaded with a distributed load.
Thank you
Thank you






RE: Allowable stress and deflection on multiple-span supports
For 3 Spans, Beam/Deflection Diagram #36, page 2-308
For 4 Spans, Beam/Deflection Diagram #39, page 2-309
RE: Allowable stress and deflection on multiple-span supports
If you have the ninth edition of the ASD Manual for Steel Construction [Green Book], Deflection in a continuous beam with three equal spans is shown on page 2-308.
The allowable bending stress in the beam will depend on the beam section properties and laterally unbraced length. See Chapter F, Section F1 (page 5-45) of the same manual for the applicable formula. Allowable shear stress is shown in the same chapter in Section F4 (Page 5-49).
Hope this helps.
JS.
RE: Allowable stress and deflection on multiple-span supports
I don't have the book and i search on the internet and the book is too expensive. The problem that I want to resolve is for three spans or more with equal length. Can you say to me what's the general formula? For the 3 spans I solve the values of the reactions but i don't have enough knowledge to go much far.
RE: Allowable stress and deflection on multiple-span supports
For any beam with moments Ml and Mr, use the following expressions:
E*I*Dx = ( p*L^3/24 + L/3 ( Ml + Mr/2 )) X – mx
Where:
Dx = Deflection at a distance X from the left support
p = T/m (force/length)
mx = X^3/6 ( Rl –p*X/4 ) + Ml*X^2/2
Rl = p*L/2 – (Ml-Mr)/L
Ml ( Mr ) = Moments at the left (right) supports, positives causing traction at the lower part of the beam.
If Ml = Mr = 0 (simply supported),
E*I*Dx = p*X*L^3/24 ( 1 – 2* N^2 + N^3),
With N = X/L
I hope it helps.
RE: Allowable stress and deflection on multiple-span supports
http://www.kmitl.ac.th/engineer/civil/ci...