How to setup rigid outriggers

[cannibalflea]

Hi all,

I'm new to using SAP2000. I have experience with other (mostly in-house) FE software. I now need to model a really long steel beam (56 meters) which is being lifted at each end. A big concern is lateral torsional buckling. Normally this would not be a problem and analytical/empirical solutions in articles would cover this situation, but I am not quite sure if any particular situation in literature addresses this. So we have decided to use and FE model for this. I have modelled the beam using shell elements as well as the lifting brackets on each end using frame elements. I've included the cable elements as well. The problem I am having is how to model the rigid links between the beam and the end brackets and the end bracket and the cables (see pictures attached). I have attached my SAP model for review. I have tried constraints and link elements, but for some reason I am getting huge deformations in these elements. I have even tried to use dummy elements but no matter how rigid I make it, it seems to make no difference.

Any help is greatly appreciated.
Al

 

[IJR]

Why would you do nonlinear analysis for lateral torsional buckling. What are you expecting from your model.

Longer beams have been designed for LTB using standard code equations.

I think you should try Ansys if you are really into buckling analysis. SAP2000 is fine with elastic critical buckling of frame elements, but I am not sure it will catch LTB.

hope this helps