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How is the response factor calculated?

Answer: ETABS and SAP2000 calculate response factor (RF) using the following equation:

  • RF = [2.31 – 0.41 log (100 (Case + Link damping, express in ratio))] / [2.31 – 0.41 log (100 (Function damping, express in ratio))]  [1],[2]


  1. Newmark, Nathan M.; Hall, William J. Engineering monographs on earthquake criteria, structural design, and strong motion records. Berkeley, CA: Earthquake Engineering Research Institute, 1982. Print.

  2. Comartin, Craig D.; Niewiarowski, Richard W. ATC-40, Seismic Evaluation and Retrofit of Concrete Buildings, Volume I. Redwood City, CA: Applied Technology Council, 1996. Print.