Seismosoft | Earthquake Engineering Solutions

In adaptive pushover analysis of a 3D building model should i apply the displacement in perimeter nodes of each direction, in all nodes of the structure, or i can assign just one displacement in a centre node?

In my model (1 storey building with lamped mass at columns) in the X-direction i got the same results either with placing the displacement in one node at the centre or at all perimeter nodes. However in the Y-direction when i applied the displacement in perimeter nodes i got a base shear of 10000kN where when i applied the displacement in the centre node i got a base shear of 20000kN. Can you please explain me the reason for this huge difference? Which of the two is correct? Thank you.

any suggestion from the seismosoft support?

Hi,

The nodes that you select to apply the displacements my have indeed some influence in the analysis results. Especially if you have significant variation in the stiffness of the vertical elements, and/or in-plan stiff slab.

In my opinion the best way is to apply the loads in all nodes of the storeys.
Note however that you might have some analysis incompatibility if you run an adaptive pushover with in-plan rigid slab.

Cheers,
Romain

Kallanis,

As hinted by Romain, your results seem to indicate a significant role played by plan irregularities in the y-direction, and/or torsional effects.

In order to try to understand which loading configuration may the more correct one, you may wish to pay a careful look into the deformed shape of your structure under the two different loading conditions, to appreciate which seems more realistic or feasible (e.g. one of the load distribution options may be implying unrealistic slab deformations).

Another option, of course, would be to run nonlinear dynamic analysis and compare the results with its pushover counterparts.

Seismosoft Support