Simple beam but large displacements
Simple beam but large displacements
(OP)
I have a simply supported W27x281, 10ft long, 100kip/ft. Basic beam equations give a displacement of 0.065in.
I model the beam in STAAD (single element), and get 0.065in. However, once I model the beam as ten 1ft long elements, I get a deflection of 0.109in.
Anyone else have this sort of problem? Or suggestions on how to fix the issue?
I model the beam in STAAD (single element), and get 0.065in. However, once I model the beam as ten 1ft long elements, I get a deflection of 0.109in.
Anyone else have this sort of problem? Or suggestions on how to fix the issue?





RE: Simple beam but large displacements
When you subdivide the beam the program is calculating deflections at the beam ends including shear deflections. You should get the same result with just two beams, with a node at mid-span. Because you have a short span (in relation to the beam depth) and a high load the shear deflections are significant.
If you switch off shear deflections (assuming STAAD allows you to do that) you should find the result agrees exactly with the basic bending formula.
Of course in this case the calculation including the shear deflection is more correct (assuming the support at one end allows lateral movement).
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Simple beam but large displacements
RE: Simple beam but large displacements
For my final calculation, I will have to account for the shear deflection. Thanks again.
RE: Simple beam but large displacements
we get paid for them (in a later life, that is).
RE: Simple beam but large displacements
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask