Pushover curve and Hinge results

[RK Sriwastav]

I have been doing pushover analysis of a distributed mass 3D model with rigid floor diaphragm.
The model is 6 storied, 4x4 bay with 5mx5m bay width, 3.5m storey height OMRF building

My questions are

Is it possible to get negative base shear in pushover analysis ?

And why are the hinge results so random for M2 and M3 hinges ?

How pushover curves (Base shear vs Roof Displacement) are related to hinge backbone curve ?




Ravi K

 

[RK Sriwastav]

Please have a look into this pushover curve. It is giving negetive base shear at the end regions.

Ravi K

 

[dik]

I would guess that the negative shear is possible due to residual stresses in pushover.

Your data does not make any sense to me because I don't know the terminology the program uses.

I would not design a 6 storey building using plastic analysis, in particular, having 'rigid' floor diaphragms. Rigid gives me the impression of being very (infinite?) stiff. If all your members are sized on plastic capacity, the entire structure can become a mechanism at once. You may want to step back and have another 'look'.

Just because you can do something, doesn't mean you should.

Dik

 

[RK Sriwastav]

When I removed the initial static load due to the self weight of the structure before carrying out pushover. The resulting pushover analysis is not showing any negative base shear.

The model must be having some mistake because of which it is showing negative Base shear. Still i have few questions:

And why are the hinge results so random for M2 and M3 hinges ?

How pushover curves (Base shear vs Roof Displacement) are related to hinge backbone curve ?

Please look in the attachment.

Ravi K