I made a model of a fixed-free steel column. I defined the elasto-plastic stress-strain curve of the material and applied a very large lateral force to the top of the column. Then i ran the analysis, but i didn't notice any indication of failure happened as if the stress-strain curve of the material is linear.
Dear Abdelrahman,
SAP2000 provided martial non-linearity as follows:
1- Bending and axial non-linearity for hinges in static pushover analysis
2- axial non-linearity for links in static and dynamic analysis
3- bending non-linearity for multi-layer composite shells in static analysis
regards
I really appreciate your help, Dr. Mitesh and Dr. Ahmed. Thanks a lot.
Dear Abdelrahman,
please find me answer below
https://www.researchgate.net/post/How_to_define_plastic_hinge_for_cold_formed_steel_in_SAP_2000
I've read in "CSI reference manual" that i can use the automatic properties provided by the program which are calculated according to "FEMA 356" or "Caltrans". Iam working on a space truss, so I chose table 5-6 concerning steel members subject to only axial force.
As with every "automatic" option for anything in our world, you should be very cautious with FEMA-356 or Caltrans Hinges. You should see for your element what is the expected hinge behaviour according to FEMA 356 and compare it with what you get actually. Also in general the sudden strength drop in FEMA-type hinges is omitted in SAP2000. In the software the negative slope is taken as 10% of the elastic slope, which could be far different for non-conforming (low dissipative) structural members.
You're right. But, fortunately, there's an alternative for the sudden strength drop. The following quotation from "CSI reference manual" clarifies this point :
(To help with convergence, the program automatically limits the negative slope of a hinge to be no stiffer than 10% of the elastic stiffness of the Frame element containing the hinge. If you need steeper slopes, you can assign a hinge overwrite that automatically meshes the frame element around the hinge. By reducing the size of the meshed element, you can increase the steepness of the drop-off).
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