Topic: Steel frame with masonry infill

Hello,

we have been modeling steel frame with masonry infill in order to simulate realistic situation obtained from experimental testing. We have some difficulties with modeling in ATENA and I will be very grateful if somebody would find time and help us.
First, there are two questions regarding steel behavior modeling, because we first want to check behavior of the bare steel frame and compare obtained results with other software calculation results as well as with our performed experimental results.
It seems that the only material model applicable for steel is bilinear model (with or without hardening effect)? If it is so, how one could limit the strain level on acceptable (realistic) values in order to avoid unrealistic situations and unnecessary too long calculation? 

The other question is related to calculation results  - as it can be noticed  from attachment, we defined ideal elastic-plastic model (without hardening effect) but obtained displacements show permanently growing? Also,  there is a noticeable difference between results from ATENA and the other software (ROBOT, Seismostruct)...

I have tried to include attachment with model data and pictures with results comparison, but I don't know how...

Thank you in advance...

MD

Re: Steel frame with masonry infill

Hello,
yes, for volume elements, the current ATENA version only offers bilinear steel material. The simplest way is to check the strain limit in postprocessing. You can also define a monitor for max. strain.

You can send your model to our general email (which can be found, among other places, at the Company page of our web). Include a description of what you are modelling and your ATENA User ID (WR) and what you do not like about the obtained results.

Just a guess without seeing your model: for steel frames, buckling of a beam or just its flange, frequently determines the max. load. Are you sure your mesh is good for bending in regions where buckling can develop? If you are using volume elements, this means min. 4 finite elements per thickness for qualitative-only results. Alternatively, you can use Shell elements.

Re: Steel frame with masonry infill

Thank you very much for your prompt answer. I will soon send our model and other data on the mail you recommended. The dimensions of steel frame are chosen to avoid local buckling problems, and we didn't notice such a problems during our tests on real models, so that I think it wouldn't be a problem, but we will appreciate if you could check...
Best regards,

M.D.
Croatia