I have programmed an Euler-Bernoulli beam, supported on springs, using both SAP2000, and by using the stiffness matrix method in MATLAB.
The nodal (joint) displacements calculated due to an applied load agree closely between SAP2000 and the MATLAB model. The rotations sometimes disagree. Anyone know why this might be?
What solution procedure does SAP2000 use that might account for these differences?
Thank you.
You are sure that it is Bernoulli beam in SAP2000?
I believe it is Timoshenko beam in SAP2000. Try to set shear area to zero and then compare results.
Thank you! So it turns out SAP2000 uses a Bathe & Wilson formulation, similar to Timoshenko.
Hi,
As far as I know, the beam element in SAP2000 is defined taking into account the shear effect. Mass matrix is lumped mass type. My modal results are completely indentical to the ones obtained using SAP2000.
The stiffness matrix and mass matrix should be set completely identical between SAP2000 and your code.
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