Bi-directional excitation and element force recording

[tugce]

I am performing nonlinear time history analysis on CBFs by applying bidirectional earthquake ground motions (horizontal and vertical). I have used the timeSeries command to define the two different GM records and applied them to the system by using the UniformExcitation pattern (with different directions 1 and 2). The code works very well; but, the differences b/w the results (e.g. member forces) that I obtained from the bidirectional and uni-axial analysis are negligibly small, regardless of the GM record and this led me to question my analysis and the way that I applied the excitation. I wonder whether I need to smt different to record the element forces or nodal displacements/reactions in bidirectional dynamic analysis to reflect the effect of vertical excitation on the response quantities ?

Thanks.

[fmk]

what is the model.

[shimasdz]

Dear Tugce,
I have the same problem. I have a 3D soil column which I wanted to apply x and y direction acceleration via uniform excitation pattern. but there is no difference btw bidirectional analysis and 1 direction (for example only x direction acc) analysis. I am wonder maybe I have problem to way I apply uniform excitation code and the way I record them. could you please help me?