a question about static pushover analysis

yuxiang-1124 · Post by **yuxiang-1124** » Thu Jul 12, 2007 6:44 pm

i just built a simple one degree freedom cantilever column which use fiber section,the column is 20m high.then i perform a static analysis.at the end when the pushover curve which is relationship of base shear and control piont displacement is ploted,i find the curve without degressive segment,so i can not judge which piont is the ultimate state of the stucture.but the pushover curve got from sap2000 has degressive segment. so i wanna know is there any method in opensees to get pushover curve with degressive segment? thanks!

pejman_opensees · Post by **pejman_opensees** » Sat Jul 14, 2007 6:48 am

I think you mean descending branch. In order to have descending branch, plastic hinge should be created in combination with consideration of geometric nonlinearity. This is just a simle energy relationship which is Energy=force * deformation. So if deformation increases significantly, in order to have constant energy variation to satisfy equilibrium, foces should decrease. Therefore you need to change Transformation command to corotational and use fiber plastic section to account for both material and geometric nonlinearity then you will definitly have descending branch if you set the analysis parameters suitably.

yuxiang-1124 · Post by **yuxiang-1124** » Thu Jul 19, 2007 4:50 am

thanks your detailed explanation ,i will try your method.