Seismosoft | Earthquake Engineering Solutions

Hi.
I have modeled a two-dimensional reinforced concrete frame in SeismoStruct and performed a pushover analysis on it. In the Loading Phases tab, I need to enter a value for the step. When I use different step values, the capacity curve of the frame changes and the ultimate displacement also varies.

However, since the frame model is the same, I expect the capacity curve to remain unchanged.

How can I determine the optimal step value and the correct ultimate displacement for the analysis?

In the Loading Phases module the maximum pushover displacement or the maximum load factor, and the number of loading steps is specified by the user. Usually the maximum displacement should be at least 150% of the target displacement, and preferably beyond the yield of the structure.
Seismosoft Support

Thank you very much for your response. It seems that I was not able to explain my problem clearly. I am aware of the points you mentioned. However, my question is this:

When a specific value is assigned as the ultimate applied displacement in the pushover analysis of the specimen, changing the number of loading steps results in a different maximum displacement capacity of the specimen.

What is the reason for this behavior, and how can it be resolved?

If I try to solve a nonlinear problem with a target displacement of 10 inches, I will expect different results if I try to solve the problem two ways: once with a step size of 2 inches (5 steps, 20% of the target) and a second time with a step size of 0.02 inches (500 steps, 0.2% of the target). The second solution with a much larger number of steps would invariably (it would seem) be more precise and more accurate. Of course, if everything stays linear, the two solutions would be virtually identical. The nonlinearity is the issue requiring a large number of steps, a small step size.

Indeed, the response in nonlinear analysis depends on the loading history (contrary to linear analysis).
Seismosoft Support