displacement time history results

[kishor]

Hello Everyone

I am wondering with my displacement time history results using OpenSees. Some times, I am getting funny displacement time history results and it goes far out of the centre. For example, Please take a look the figure in link:

http://www.imgplace.com/viewimg688/149/ ... timehi.jpg

I am getting a good match with the test results in figure A. When I slightly changed the stiffness of diaphragm to look what it does, I got flying displacement at the end of analysis. how can I control this? Please help me. If I change only time steps from 0.01 to 0.001 Sec as compared to figure B again, It shows in figure C that I might get better results. But this is still not conviencing. Help needed please!

[kishor]

Just bit more about my model. I used pattern UniformExcitation command to give acceleration input in the short direction of diaphragm only. I have used Pinching4 material for nonlinear response. Hope some one will give hint why I am getting the unusal displacement time history.