Fiber section in pushover analysis

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LeandroC
Posts: 2
Joined: Wed Mar 02, 2016 7:38 am

Fiber section in pushover analysis

Post by LeandroC »

Dear all,

I have unsuccessfully tried to run a nonlinear static analysis with displacement control for a simple beam in a four point bending test configuration.
The model has 4 nonlinearbeamcolumn elements between five aligned nodes. The first and fifth nodes are the supports, while the second and fourth ones refer to the nodes of load application. The third node refers to the midspan point whose I wish to monitor displacement.
In such a scheme, I can obtain as an output, the total applied load vs midspan deflection curve and the moment vs curvature relationship which I will compare with the outcomes of an experimental campaign. Since I am considering FRC members, it shall be convenient to use Pinching4 model.
By the way I have really basic problems with the analysis.

Specifically, I can run the analysis if both supports are fixed to the ground. But this implies that the longitudinal deformation of the beam is constrained and therefore an axial load arises so that the resisting moment is affected as well. Therefore, I obtain a resisting moment that is much higher than the experimental one.
To avoid such a problem I tried to fix a single point in the horizontal direction (I prefer the central point), but suddenly something wrong occurs and the solver is early not able to find the solution.

I have tried different combinations of solver and convergence tests, as well as load application types (load control or displacement control) but nothing worked properly.
Is anybody around able to help me out with this issue?
I can share the code I am working on, if necessary.
bahramabdollahi
Posts: 7
Joined: Sat Mar 12, 2016 6:32 am
Location: Iran

Re: Fiber section in pushover analysis

Post by bahramabdollahi »

hi
i think
it's useful to increase the number of integration points in nonlinearbeamcolumn elements.
fmk
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Location: UC Berkeley
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Re: Fiber section in pushover analysis

Post by fmk »

might be more useful to use dispBeamColumn as opposed to the forceBeamCoulmn as you have already discretized the beam and the forceBeamColumn (nonlinearBamColumn) may not be provding additional benifits.
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