Seismic Testing of Eccentrically Braced Dual Steel Systems

Abstract

Two six-story eccentrically braced dual steel systems (EBDSs) were tested as part of the U.S.-Japan Cooperative Earthquake Research Program. The first, a full-scale structure ( prototype) was pseudo-dynamically tested in the Large Size Structures Laboratory of the Building Research Institute in Tsukuba, Japan. The second, a similitude scaled replica of the first, was tested on the earthquake simulator at the University of California at Berkeley. The prototype was designed for the minimum earthquake forces specified by the 1981 Japanese Aseismic Code and satisfied the current earthquake-resistant design regulations in the U.S.A. (1985 UBC, 1984 ATC 3-06 and 1986 SEAOC). The performance of the EBDS (both prototype and model) was outstanding in terms of its elastic strength and stiffnesses during minor earthquake shaking and its ability to absorb and dissipate energy, without strength and stiffness degradation, during severe earthquake shaking. Substantial overstrengths of both EBDSs with respect to their nominal yielding strengths were observed during severe earthquake shaking. However, the response modification factors currently adopted by the ATC and SEAOC significantly overestimated the experimental values in both instances.