Report - PEER - University of California, Berkeley

tests of its type ever conducted. The frame was tested using the pseudo-dynamic testprocedures applying input ground motions obtained from the 1999 Chi-Chi and 1989Loma Prieta earthquakes, scaled to represent 50%, 10%, and 2% in 50 years seismichazard levels. Following the pseudo-dynamic tests, since none of the brace wasfractured, quasi static loads were applied to cyclically push the frame to large interstorydrifts up to the failure of the braces. Being the largest and most realisticcomposite CFT/BRB frame ever tested in a laboratory, the tests have provided aunique data set to verify both computer simulation models and seismic performanceof CFT/BRB frames. This experiment also provides great opportunities to exploreinternational collaboration and data archiving envisioned for the NetworkedEarthquake Engineering Simulation (NEES) program and the Internet-basedSimulations for Earthquake Engineering (ISEE) (Wang et al. 2004) launched recentlyin USA and Taiwan, respectively. This paper describes the analytical predictions andthe experimental results, and evaluates the seismic performance of the framespecimen. Inelastic static and dynamic time history analyses were conducted usingPISA3D (Lin and Tsai 2003) and OpenSees (Open System for EarthquakeEngineering Simulation), developed at National Taiwan University and PacificEarthquake Engineering Research Center (PEER), respectively.2. A FULL SCALE CFT/BRB COMPOSITE FRAMEThe 3-story CFT/BRB frame shown in Fig. 1 is employed in this experimentalresearch. The prototype three-story building consists of 6-bay by 4-bay in plane. Inthe two identical prototype CFT/BRB frames, only the two exterior beam-to-columnjoints (Fig. 1) in each floor are moment connections, all other beam-to-columnconnections are assumed not to transfer any bending moment. The BRBs are installedin the center bay. Square CFT columns are chosen for the two exterior columns whilethe center two columns are circular CFTs. Story seismic mass is 31.83 ton for the 1stand 2nd floors, 25.03 ton for the 3rd floor for each CFT/BRB frame (half of thebuilding). The material is A572 Gr.50 for all the steel beams and columns, while thecompression strength fc’ of the infill concrete in CFT columns is 35MPa. In all theanalyses, the material’s strength for steel and concrete is based on the actual strengthobtained from the material tests. The supporting beams above the BRBs satisfy thecapacity design principle considering the strained hardened BRBs and an unbalancedvertical load resulted from the difference of the peak BRB compressive and tensilestrengths. The fundamental vibration period is about 0.68 second. Three differenttypes of moment connections, namely through beam, external diaphragm and boltedend plate types, varying from the first floor to the third floor were fabricated for theexterior beam-to-column connections. Three types of BRBs, including the singlecore,double-cored and the all-metal BRBs, were adopted in the three different floors.In particular, two single-cored unbonded braces (UBs), each consisting of a steel flatplate in the core, were donated by Nippon Steel Company and installed in the secondfloor. Each UB end to gusset connection uses 8 splice plates and 16-24mmφ F10T246