Abnormal acceleration response of the SDOF model

[wsadwsad]

Dear STKO team:

I built a simple single-degree-of-freedom (SDOF) model in STKO to perform time history analysis. The model includes two nodes and one zeroLength element. The zeroLength element was assigned with Steel01 material. The yield strength was 10 times ite weigth (Fy = 10mg). I adopted "MultiSupport" to input ground motion so that I can obtain the absolute acceleration response directly. But the obtained acceleration is abnormal. Since the SDOF system is relatively rigid, the acceleration response is expected to equal the input ground motion. But the calculated acceleration response is very confusing, and I don't know what caused it.

[STKO Team]

It's the amplification due to yielding. try with an elastic material and there should be (almost) no amplification

[wsadwsad]

Your answer is much appreciated. However, actually the problem stems from a part of inelastic response spectrum analysis. So time response analysis of short-period, i.e. very stiff, nonlinear materials is a necessary process. I am wondering if there are other means to get reasonable acceleration results without changing the material parameters?

[kesavapraba]

You may try other uniaxial material models without changing the material properties. Also, explore different analysis settings, particularly with different transient solvers.