3D RC frame with the Capacity Design

[geoStru]

Hi everyone.
If I would like to study (with the analysis pushover) the beahviour and ductility of 3D RC frame with the teoric model of "Capacity Design", should I build the beam with "element beamWithHinges"?

In this type of element are Lpi and Lpj at the node i and j similar than nonlinearBeamColumn?
For the columns at floor 0, where there are the plastic hinges (during the earthquake) only at the base, could I use this element with Lpj = 0?

Or is it better to use 3 node for element (column at the base)? for example:
node 1 0. 0. 0.
node 2 0. 0. 1. #length of plastic hinge
node 3 0. 0. 3. #end of column
element nonlinearBeamColumn 1111 1 2 [...]
element elasticBeamColumn 1112 2 3 [...]

[mhscott]

You can build the model however you would like. Yes, you can set lpI and/or lpJ equal to zero. lpI and lpJ are integration weights.

nonlinearBeamColumn and beamWithHinges both use the same force-based formulation. There is no real difference.

Here are a couple obscure posts about it
https://wp.me/pbejzW-m
https://wp.me/pbejzW-8n

[selimgunay]

Because capacity design for strong colum/ weak beam is based on the equilibrium of a joint and based on satisfying sum(Mc)>1.2sum(Mb), depending on the redistribution of the forces around the joint and strain hardening effects, etc, you can have plastic hinge formation at the top of the column in later steps of the pushover. Therefore it is better to put the inelastic regions in all elements and let results of the pushover show you if there is a plastic hinge happening at the top of a bottom story column or not.

[geoStru]

Yes, I know the proc for valuate the behavior of 3D RC frame with the capacity design.
But, probabily, my professor would like to study the teoric "L" behavior of 3D RC frame and the reduction of ductility of columns with different eartquake angles.

First I used nonlinearBeamColumn for the diffuse plasticity of by beams and columns.
Now I should consider the diffuse plasticity only in the regions where that should be the plastic hinges (base of the columns and ends of the beams).
I read the paper and I think "element beamWithHinges " could works. It could be right?

[mhscott]

Try it. See what happens. Most of nonlinear analysis is trying different things and seeing why the results change.

[selimgunay]

It doesn't hurt to put plastic hinges at all locations. If they remain elastic, the analysis results will show you. If you assign the inelasticity to only the intended locations, that is not a correct approach as the behavior may not be exactly as intended.