Earthquake Simulator Testing of Concentric Braced Dual System

Abstract

A six-story concentrically chevron–braced dual-steel system is subjected to 20 earthquake ground motions with effective peak accelerations of up to 0.40 g on the earthquake simulator at the University of California at Berkeley. The design of the structure has been reviewed in accordance with the 1979 Uniform Building Code. The construction, dynamic characteristics, and experimental behavior of this test model are discussed. The structural strength is reached after severe buckling and ruptures of the concentric braces. The reduction of elastic strength demand due to developed ductility is on the order of 1.5. A substantial overstrength on the order of 2.4 with respect to the nominal yielding strength of the structure is observed and its importance is discussed in terms of the values of the response modification factor adopted by the Applied Technology Council (ATC). Based upon the test results, the role of the ductile moment-resisting space frame in the dual system is discussed. Conclusions are drawn regarding the suitability of the response modification factors recommended by ATC. To prevent and/or to delay severe buckling and rupture of the braces, improvement in their proportioning for this type of system is suggested.