Report - PEER - University of California, Berkeley

DISPLACEMENT BASED SEISMIC DESIGN AND PERFORMANCEEVALUATION TESTS OF A FULL-SCALE BRB COMPOSITE FRAMEK.C. Tsai 1 , Y.T. Weng 2 , M.L. Lin 3 , C.H. Chen 3 and P.C. Hsiao 4ABSTRACTThis paper introduces a full-scale 3-story 3-bay CFT buckling restrained braced (CFT/BRB)frame specimen tested recently in the Taiwan National Center for Research on EarthquakeEngineering using pseudo dynamic test procedures and internet testing techniques. The testframe was loaded to simulate the responses under ground motions corresponding to earthquakehazards for a highly seismic location with 50%, 10%, and 2% chance of exceedance in 50years. The frame specimen was designed by displacement-based seismic design (DSD)procedures considering a target inter-story drift limit of 0.025 radian for the 2% in 50 yearshazard level. This paper summarizes the analytical studies made before and after the tests andevaluates the frame performance. CFT/BRBF performed extremely well after the application ofsix earthquake load effects. Very minor changes on stiffness and damping were observed asevidenced from the free vibration tests conducted after each earthquake pseudo dynamic test.The peak story drift reached 0.023 radian at the first story after applying the 2/50 designearthquake on the specimen. Tests confirmed that the DSD procedure adopted in the design ofthe specimen is effective in limiting the ultimate story drift. Tests also confirmed that theresponse of the CFT/BRB frame can be satisfactorily predicted by using either OpenSees orPISA3D.Keywords: Concrete filled tube (CFT); Buckling restrained brace (BRB); Passive control;Displacement-based seismic design; Networked pseudo dynamic test; Nonlinear analysis.1. INTRODUCTIONIn October 2003, a full-scale 3-story 3-bay CFT column with the buckling restrainedbraced composite frame (CFT/BRBF) specimen (Fig. 1) was tested in a Taiwan-US-Japan Cooperative Research Program (Tsai et al. 2004, Chen et al. 2004, Lin et al.2004). The 3-story prototype structure is designed for a highly seismic location eitherin Taiwan or United States. The typical bay width is 7m and typical story height is4m. The total height of the frame, including the footing, is about 13m. The 2.15meters wide concrete slab is adopted to develop the composite action of the beams.Measuring 12 meters tall and 21 meters long, the specimen is among the largest frame1 Director (kctsai@ncree.gov.tw),2 Postdoctoral Researcher,3 Associate Research Fellow,4 Graduatestudent, National Center for Research on Earthquake Engineering, 200, Sec.3, Xinhai Rd. Taipei, Taiwan245