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[GEN/Pushover]Can Response Modification Factor Be Determined Using Pushover Analysis?

Question

I have a question about how to determine the response modification factor using Pushover analysis.

We are conducting a stability assessment for an existing building. The existing building is a typical moment frame with a response modification factor (R) of 3.0, and the additional part being added to it is a shear wall structure.

When a general analysis is performed on the existing building with a response modification factor of 4.5, the bottom shear force is approximately 4200 kN, and when a response modification factor of 3.0 is applied, the bottom shear force is approximately 6300 kN.

When we performed Pushover analysis on this building, the bottom shear force at the performance point was 3670 kN. In this case, can we select a retrofit element by applying R=4.5 based on the fact that the bottom shear force obtained from Pushover analysis is close to the bottom shear force obtained when R=4.5 is applied? When R=3.0 is applied to a typical moment frame, there is concern that too many seismic retrofit elements will be required.

 

Answer

Simply put, you cannot determine the response modification factor based solely on the bottom shear force at the performance point.

In Pushover analysis, assuming that the Capacity Curve is well-defined, you can evaluate the building's elastic performance based on the ratio of dmax (the displacement at the point of failure) to dy (the yield point displacement) and this ratio (dmax/dy) can be used to assess the building's ductility.

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