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 fa ctor are based on engineering judgment and have little sound technical basi s. Any improvement in the reliability of modern earthquake-resistant buildi ngs in the United States will require the systematic evaluation of the buil ding response characteristics that most affect the values assigned to the f actor. To this end, a draft formulation that represents the response modifi cation factor as the product of factors related to reserve strength, ductil ity, and redundancy is presented in the paper. Pertinent data from various analytical and experimental studies on reserve strength and ductility are a lso presented.