Incremental Dynamic Analysis

Derya Deniz · Post by **Derya Deniz** » Fri Oct 02, 2009 11:58 pm

Hi,

I am trying to do Incremental Dynamic Analysis. As I understand, I only need to scale the gorund motion and do time history analysis each time.
I started with an example from the manual.

source Ex8.genericFrame3D.build.Wsec.tcl
source Ex8.genericFrame3D.analyze.Dynamic.EQ.Uniform.tcl

It seems this example is already using an inelastic section. I only changed the scale factor in the analysis part from the command below:
set GMfact 1; # ground-motion scaling factor
(The factors I used are 0.25, 0.5, 0.75, 1,... 8. After the scale factor of 8, it started to give convergence warnings.)

I was expecting a nonlinear IDA curve with a flatline (indicating instability-collapse) at the end, but I got a linear behaviour instead, without any indication of inelasticity and instability of the structure (no flatline at the end) like an elastic material.

Can you please help me to solve my problem?

Thanks,

Derya

silvia · Post by **silvia** » Sat Oct 03, 2009 7:18 am

an elastic analysis has no collapse.
you need to read-up on IDA.

Derya Deniz · Post by **Derya Deniz** » Sat Oct 03, 2009 11:37 am

I know that there is no collapse for an elastic analysis. I assumed the type of analysis you used in your example 8 was inleastic. Am I wrong? Is it an elastic analysis?

silvia · Post by **silvia** » Mon Oct 05, 2009 7:42 am

ops, i misread.
however, i think the models in example 8 don't have any strength degradataion, just stiffness.