Seismic response modification factors

The response modification factor plays a key role in the seismic design of new buildings in the United States. To date, the values assigned to this factor are based on engineering judgment and have little sound technical basis. Any improvement in the reliability of modern earthquake-resistant buildings in the United States will require the systematic evaluation of the building response characteristics that most affect the values assigned to the factor. To this end, a draft formulation that represents the response modification factor as the product of factors related to reserve strength, ductility, and redundancy is presented in the paper. Pertinent data from various analytical and experimental studies on reserve strength and ductility are also presented.