odd behavior with gap element?

[jefferyr]

Hi,

It's been a long time since I've had a question.

I have a bridge model, on which I have abutments being simply modeled with gap elements and truss elements. I know that the zero length element should be used here, but I didn't know about it when I made the model. Anyway, I have checked the abutment node reactions to make sure that there is the proper amount of load being supplied by the gap element in the proper direction. It seems to be working properly. When I have the gap element fy being essentially zero, there is little load from the abutments, and I get reasonable results when applying earthquake records. I think they're reasonable result since they are "close" to numbers from a displacement spectrum I made for the EQ records used (2 EQs used per model). But when I give a slope and higher fy for the gap element, the displacements increase. I would expect that the displacements would decrease since there is a reaction pushing back through the gap element.

Do you have any thoughts on what could be 'amplifying' the horizontal displacements?

I can email some of the tcl code if you have time to look at it.

Thanks,

Jeff

[jefferyr]

Hello again,

I've remodeled using zeroLength elements with similar results. The results aren't "exact" but "close". Any ideas on why there would be any differences?

Jeff R

[LWxiake007]

Dear jefferyr:
I'm simulating the structural pounding of RC Frame.The same high building is my work.I used the truss element linked the same high node.I read your subject and knew you used the gap element and truss element simulate the between the two abutment.So can you provide me some suggestion about gap element?
Thank you!
LWxiake