Pushover analysis

kartheek · Post by **kartheek** » Sat Mar 05, 2005 10:29 pm

I am working to carry out a pushover analysis of a 3-d structure in opensees. Due to the graphical interface I took up Opensees Navigator. But due to the errors in 3-d model I am first working with a 2-d model. I have performed the gravity analysis and now I have to carry over the Pushover imposing lateral loads. But the calculation of lateral loads is done using base shear, which I am not able to find out. And usually in a eathquake analysis we define hinges near the nodes of a non-linear beamcolumn element. So I would like to ask :

1. How to carry out a 3-d model analysis in OpenSees Navigator ?

2. How to calculate base shear from the outputs of gravity load analysis ?

3. How to define plastic hinges near the nodes of beamcolumn elements ?

berktaftali · Post by **berktaftali** » Sun Mar 06, 2005 11:47 am

I don't know much about OpenSees Navigator, but here are my thoughts on questions 2 & 3:

2. How to calculate base shear from the outputs of gravity load analysis ?

When you are applying the lateral load pattern, make sure that the sum of the lateral loads is 1.0. Then, use -time switch in the node recorder to get the pseudo time, which is the factor multiplying the lateral loads on a displacement controlled pushover analysis. That lateral load will be resisted as shear at the base, hence the pseudo time recorded is the base shear you are looking for.

3. How to define plastic hinges near the nodes of beamcolumn elements ?

Use a distributed plasticity element (e.g. nonlinearBeamColumn) and you don't have to. If you insist on using concentrated plasticity, you can use beamWithHinges element that can form plastic hinges at the element ends.

Hope it helps...

erol kalkan · Post by **erol kalkan** » Fri Mar 11, 2005 3:47 pm

My suggestion for question 2 is that:

Record all the forces at the bottom of the first story columns in the direction of loading, sum them up at each time step of the pushover analysis. That wil give you the total base shear for each time step.

aggelos · Post by **aggelos** » Tue Apr 15, 2008 3:15 am

I am a new user of OpenSees and i have questions in basic subjects...
I have a difficulty to find and download an example of pushover analysis of a reinforced concrete column.
I would appreciate if someone could give me a link or, even better, copy-paste such an example here.
Thank you.

silvia · Post by **silvia** » Tue Apr 15, 2008 5:16 am

1. use the reaction recorder for the nodes at the base to get the base shear.

2. here is the examples manuaL:
http://opensees.berkeley.edu/OpenSees/m ... index.html