hello,I'm a new opensees'user!
I' m executing a dinamic time history analysis with opensees program, and I compare the results of this with ruaumoko2D and SAP2000 programs.
The results of ruaumoko and sap analysis are very similar, whereas the opensees results are different(15-20%).
My model is a 2D frame(4 storeys, 2bays),the elements are elasticBeamColumns.
The mass and stiffnes are the same in the three analysis,the modal periods are the same(T1=0.60 s, T2= 0.19 s), same alghorithms,ecc
I think the differencies are in the damping formulation, I apply rayleigh command:
rayleigh 0.795 0.0 0.0023 0.0;
(this values are used in sap2000)
alpha and beta values are calculates by:
alpha= 4*PI*0.05/(T1+T2)
beta= 0.05*T1*T2/(PI*(T1+T2))
where 0.05 is the percent damping
what is my mistake?thanks!
different results
Moderators: silvia, selimgunay, Moderators