Gravity Load effect on Dynamic Load

[jonade]

I have a model that has a leaning column with loads applied on the nodes of the leaning column and a uniform line load on the beam of the frame itself. I am running a time history analysis to check the response of the structure. I was expecting the response of the structure (Drift, displacement ) to increase due to the added leaning column but to my amazement, it did the opposite. The Drift ratio and the displacement decreased after adding the leaning column. This made me wonder about the effect of Gravity load on dynamic analysis so I tried running the analysis with and without gravity load applied to the moment frame including the loads on the beam of the frame and again the response of the structure without gravity load is higher than the one without it. (Note that I didn't change the mass) . I thought I might have made a mistake somewhere so I tried to check if this was true or not for the models provided by opensees official website https://opensees.berkeley.edu/wiki/inde ... ment_Frame and I had the same result. When gravity loads are not analyzed first the dynamic analysis gives a higher response. I have provided the response of the example model that is on the opensees website below.
https://1drv.ms/u/s!AhtCW7DOTIr6mVvCrYj ... i?e=jaQA6u . This is a link to see the difference in displacement .
https://1drv.ms/u/s!AhtCW7DOTIr6mhCDL2D ... s?e=sKvW5N . This is a link for the two models. The only difference between the two is that for the model without Gravity load the Gravity loads are commented out. If anyone can explain to me this phenomenon it would be appreciated. The results are against my intuition.

[mohammmad]

Hello,
download the following PDF, maybe it can help you.
http://dl1.iarchitect.me/Standard/OpenS ... ct.me).pdf




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[jonade]

Thank you very much