Vibration of a Simple beam under compression?

[lukeme]

Dear friends,

How can I determine the transverse natural frequencies of simply supported beam under an axial compressive loading?
When I apply the loading at supports, no changes in the freqeuncies occur beacuse, I guess, the beam does not feel it is under axial loading. Specifcally, how can I make the beam know that it is compressed while it s transversely vibrating?

Please help. Thank you..

Luke

 

[stressed]

When you say that you apply the load at supports, please make sure you are not restraining the frame on both ends in the direction of loading. Starting in version 9 (or was it 8?), SAP enables you to run a modal analysis on a stressed case. You will need to go to Define menu>analysis case and modify 1 or more of your load cases to be nonlinear. Then modify your Modal case from unstressed state to follow one of the nonlinear cases and that should work

 

[lukeme]

Thank you stressed..

I got it

Luke