question on example 2

yuejun · Post by **yuejun** » Fri Jun 26, 2009 12:34 pm

Example2b.Canti2D.InelasticSection.Push
When I ploted restoring force vs. displacement at node 2, I found the stiffness decreased around 302 kip because of yield. However, it decreased for a 2nd time around 364 kip, corresponding to a displacement of 18 in.
In this example, steel01 is used to model the moment-curvature behavior. And it is defined as a bilinear material. So how does the 2nd stiffness decrease come?
By the way, 18 in displacement is a 4% drift that is not a small one and might cause plastic hinge. But this behavior is not defined in the model. How can it come?
Thanks.

silvia · Post by **silvia** » Fri Jun 26, 2009 8:54 pm

look at the section response.
it might be the concrete....

yuejun · Post by **yuejun** » Mon Jun 29, 2009 7:12 am

It might be because of the way how the model is defined. In this example, the steel01 is defined by moment and curvature relationship. So I checked these two variables at section 1 (node i), as shown in:
[img]http://picasaweb.google.com/lh/photo/mH ... directlink[/img]
It is exactly the steel01 model.
This is a figure of lateral displacement vs. restoring force at node j.
[img]http://picasaweb.google.com/yjyincj/Ope ... directlink[/img]

silvia · Post by **silvia** » Mon Jun 29, 2009 8:31 am

yes, i was just trying to do a simple example, not a realistic one.