Non-Linear Pushover Analysis

[thewhitehair]

Hi,

Can someone please clarify some things for me. I am new to sap0000 and trying to figure out how to work with non linear analysis. For a simple introduction I just made a cantilever beam with a load at the tip. I defined a time-history function with a load that should start in the elastic range and end in the plastic range for the section and material I used.

I defined a frame hinge in at the base of the beam in order to get the plastic deformation in the right place.

My question is about what load case I should use. When I watch the CSI tutorials on youtube they use an acceleration in a non linear static analysis but the results I get for that dont make any sense. So I used the time history function I defined and got results that make some sense, the beam yields but not at the Fy=50 ksi (I used A992 steel).

Basically I just want someone to tell me how to get a cantilevered beam to behave non-linearly in the way calculate it should.

Thank you

 

[kostast88]

Could you please clarify,where is this video and what accelaeration are you talking about?

If you refer to "Accel" as a load type, in nonlinear load case window, then this is defined to tell the program that the lateral load will be incremental at say, 'UX' direction with a scale factor of either 1 or -1 (so that it will result to positive or negative displacements).

 

[thewhitehair]

Here is the link to the video,

http://www.youtube.com/watch?v=CzqZVDse-eI

When setting up the load case, they use accel like you mentioned. Is this is only way to do this?

 

[kostast88]

Yes this is how you do it for the lateral load.It is just what I wrote before.Not a "true aceleration".

What exactly doesn't make sense in the results you mentioned in the first post? Because I believe there is some confusion of static nonlinear with transient nonlinear analysis.

 

[thewhitehair]

Thank you for getting back to me. I will attach my model file on Monday and maybe you can explain to me what I am doing wrong.

 

[thewhitehair]

Here is the file. Like I stated before I used a cantilever beam and now I have applied the accel load in the load case window. The reason I dont think the results make sense is that a hinge is not formed and the deflection of the tip is linear. It should be non linear to reflect the beam yielding.

 

[kostast88]

Are you sure this is the right file?
-There are no frame hinges in this one (define->section properties->hinge properties...)
-One of your materials has a stress-strain curve to behave as tottaly elastic
-There is no nonlinear static analysis case but a direct integration one.The accel is the "Load Type" in a "Static Nonlinear" analysis,not in transient analysis.Pushover is a static analysis.

The video example is very clear on that.I suggest you perform it step by step,and then attempt to do pushover on your file.