Composite Beam Design
Composite Beam Design
(OP)
On page 5-57 of ASD Manual, for composite beam design, the calculation of transformed section properties for stress check is always based on normal weight concrete, but for deflection checks we are asked to take into account whether the concrete is normal weight or light weight. Why is it so?





RE: Composite Beam Design
Why not use LRFD composite design? The difference in results are extreme and it's also really easy to understand, unlike Allowable Stress Dinosaur's composite design, as illustrated by this thread. ;)
14159
RE: Composite Beam Design
RE: Composite Beam Design
The modulus of elasticity (E) for normal weight and light weight concrete is different. If you check out ACI - you'll see that for concrete - Ec = wc^1.5 x 33 x sqrt(f'c); where wc is the unit weight of concrete.
Thus, E is affected by density of the concrete. So to get accurate deflections, you must use an accurate E which is based on the unit weight.