MVLEM model - Load command and gravity load increasing period significantly

[LiamPledger]

Hi All,

I've developed a simple wall structure using the MVLEM model in OpenSeesPy. I get a period of 0.378 sec before applying gravity load. (This matches well with the SAP2000 model and hand calcs done in MathCAD ~ 0.38 s). However, when I apply gravity load using the Load command and then get the period after gravity load analysis, the period is 0.93 sec. I know there is clearly something drastically wrong however I can't work out what exactly. I have checked units and that is not the problem. I have developed an RC frame model in opensees previously and period changes approx <1% when applying gravity load.

Even changing the direction of the load to +ve (upwards) which should reduce the period by increasing stiffness leads to the same period of 0.93 sec. I have also tried changing the transformation from Corotational to Linear and this doesn't do anything.

Any help would be greatly appreciated, Cheers, Liam

[mhscott]

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