Comparative Seismic Performance of Four Structural Systems and Assessment of Recent AISC BRB Test Requirements

October 30, 2005
Publication: Eleventh US-Japan Workshop on Improvement of Structural Design and Construction Practices, Kobe Japan
Author(s): Ronald Mayes Craig Goings Naguib, Wassim I. Stephen Harris

Abstract: This paper provides a comparison of the maximum inter-story drifts and floor response spectra of both a three and nine story building each with four different steel structural systems – moment frame, buckling restrained braced frame, viscously damped frame, and a base isolated braced frame. Each of the building models were analyzed as fully non-linear structures and subjected to a total of 10 time histories each. One set of five time histories was representative of a 50% in 50 year earthquake, while the other set was representative of a 10% in 50 year earthquake. Both sets were developed for the Los Angeles area. The results of each set of five were averaged and reported separately.|The results of the non-linear time history analyses on the buckling restrained braced frame and those performed by others are used to assess the most recently recommended AISC test requirements for buckling restrained braced frames. The AISC provisions requires that the braces have adequate performance, as demonstrated by tests, for deformations corresponding to 2.0 times the design drift. This requirement needs to be increased to 3.0 times the design drift or a drift of 3% (0.03 times story height) because the drifts that result from the non-linear response of these frames for the design earthquake (especially for buildings less than approximately 6 stories high) may have significant non-linear deformations concentrated in one story height. This concentration of deformation can lead to much higher ductility demands in selected braces.