## Simulation Mechanical and Multiphysics

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# RC Column Simulation convergence problem.

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Hi,

I would like to simulate the behaviour of 750x750mm concrete column with 160mm hole in the middle and 12 vertical rebar struts of 25mm diameter subjected to a compressive force of 2000KN and moment of 750 KNm. I have modelled the column in Inventor but I am having problems with the convergence in Simulation 360. I have tried both static stress with linear materials and MES but had no success. Mesh is from brick elements, nodes of the concrete match with nodes from the rebar and all surfaces are completely bonded.

# Re: RC Column Simulation convergence problem.

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Hi javorpanev,

When you say that you are having "convergence" problems, specifically what is not converging? Here are the different things that come to my mind:

- Do you have surface contact in your model, and the iterations to determine which nodes are in contact and which ones are not is failing to find ("converge" to) the solution?
- Is the analysis using the iterative solver, which uses iterations and tolerances to converge to the solution of the matrix of equations {F} = [K]{displ}?
- Are you doing a mesh study (running the model with smaller and smaller mesh size) but the results are not converging?
- Something else?

I am not that familiar with Sim 360, so perhaps the convergence is somehow related to that?

Mechanical Engineer

Pittsburgh, PA

Simulation Mechanical user since Dec 1997

# Re: RC Column Simulation convergence problem.

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Thanks I succeded in simulating this when both the concrete and the reinforcement are behaving linear-elastically. Now, however I struggle to simulate a situation where the concrete is behaving non-linearly.

I made the whole column from reinforced concrete material and used the material wizard to upload the true stress-strain curve and Youngs Modulus of Concrete C30/37 according to Eurocode 2. I uploaded the rebar as a volume fraction in the rebar tab as described in the online help. The geometry is a simple prism 750x750x1800mm with 150mm hole in the middle.

The solver keeps reducing the time step and after reaching L value of 19 it returns "reached autotm limit". The type of solver is automatic.