SAP2000: Nonlinear Time-History analysis and plastic hinges

[wirty91]

Hello,

I have been trying to solve with SAP2000 failure mode of planar steel frame under El Centro 1940 earthquake. Static live load on the frame is 2,5kN/m^2.

My problem is this, that when I run nonlinear analysis, I'm not able to produce any plastic hinges. Even I scale El Centro earthquake with 1000 I still don't manage to produce plastic hinges which is actually little bit strange... My task is to find failure mode of this moment frame and of course I want the hinge to be formed to the beam. I have assigned hinges to columns and beams (relative distance 0 and 1).

I have attached few pictures about my project. I'm really stuck and I don't know anymore what I should do to get this to work. Do you know what I'm doing wrong?

Frame information:

http://files.engineering.com/getfile.aspx?folder=9399382a-59f4-4f66-8a25-bb942d4f6997&file=Frame.JPG

Time History function:

http://files.engineering.com/getfile.aspx?folder=0b71c8c0-51a5-42ae-be27-8758c0b9991b&file=TH.JPG

Gravity:

http://files.engineering.com/getfil...-269f-4be6-be39-9c351fc68ed8&file=Gravity.JPG

Time History in X-direction:

http://files.engineering.com/getfil...56a-81ba-c23261d4c807&file=TH_X_Nonlinear.JPG

 

[sponton]

is the result of the gravity loads analysis makes sense? the modal analysis? do you have your mass source defined? it's a shot in the dark here since you're not providing a file or results that can be used to verify.

 

[akalyoncu]

Are you sure that you assigned hinge properties correct? also nonlinear material properties(if auto or something like that)?

Also, 0.5 sec output time step seems crucible.. what do you want to do with that results.

 

[kostast88]

Check simple things first. Assign mass as masses, not from loads and try again. Check internal forces in gravity analysis and check everything is ok. If not, vheck the hinge properties you assigned, especially yield. Even units could be wrong by confusion. Also check your accelerogram uits, some are in cm/s and the scale factor for Dynamic analysis should be 98,1 instead. All these little things