Help with nonlinear hinge in pushover analysis

[ivanuccio84]

I defined a non linear hinge. In the pushover curve the moment features are OK, but I really can't understand the displacement features. The elastic part ends at the attended moment and displacement (point B), but the other point (C,D,E)? Defining the nonlinear hinge I set


moment/SF rotation/SF
point A 0 0
point B 1 0
point C 1 5
point D 0.2 5
point E 0.2 10

in the pushover curve the reaction force is ok, it's equal to moment/(column height) for all the points (A,B,C,D,E). But I don't understand the displacement, the only one that is correct is the point B. In this point the displacement is equal to the linear elastic displacement at yield limit. But the other ones?
Could you please help me?
Thanks

 

[canersoydas]

I think, you want to define a perfectly elastic-perfectly plastic nonlineer hinge. If you use steel section, yo can select "use yield rotation" in etabs, or you can define the yield rotation angle. other deformation or rotation values ,that you asked, are the times of rotation angle. you can find these values in appropriate standarts. I sent you a link, there is a FEMA 356 approach for steel beams. I think you should use a new one.

I hope it will help you.

 

[ivanuccio84]

Dear canersoydas,

I knew it. But in a pushover of e vertical cantilever beam, with a plastic hinge (previous characteristics), the pushover curve it isn't like I expected:

A 0 0 ---> correct
B 0.0261 49.19 ---> correct (yield point)
C 0.0892 49.19 ---> incorrect, I expected 6 times the deformation of the point B.
D 0.0892 9.84 ---> correct, the same deformation of C, but 0.2 of the force.

To obtain the correct result I have to use an imposed yield rotation: for a cantilever beam I used delta/H (0.0261/3).

Imposing the correct value of the yield rotation the pushover curve is:


A 0 0 ---> correct
B 0.0261 49.19 ---> correct
C 0.1566 49.19 ---> correct (0.0261*6=0.1566)
D 0.1566 9.84 ---> correct
E 0.2662 9.84 ---> correct (0.0261*10.2=0.2662)

But how Etabs find the incorrect value of the yeld rotation??