Report - PEER - University of California, Berkeley

2. HYBRID FRAME BUILDINGSTwo precast hybrid frame buildings were chosen for the analytical investigationreported in this paper. Developed from the prototype building shown in Figure 2,these hybrid frame buildings represented the prototype building at 60 percent scale.Furthermore, only two of the four bays in the prototype seismic frames were modeledin the hybrid frame buildings. These modifications were consistent with theprocedures used to create the PRESSS test building that was subjected to rigorousseismic testing (Nakaki et al. 1999; Priestley et al. 1999; Sritharan 2002). Includingthe hybrid details in the lower three floors of a seismic frame, the PRESSS buildingwas designed with four different precast frame connections.A typical floor plan and an elevation view of a typical seismic frame in thehybrid frame buildings are shown in Figure 3. As seen in the plan view, thesebuildings consisted of two identical seismic frames in one direction and a precast wallsystem in the orthogonal direction as the primary lateral load resisting systems. Theanalytical investigation was performed for these buildings in the frame direction ofresponse.4-bay seismic framePrecast wallFigure 2. Plan view of the precast concrete prototype building.The first hybrid frame building, referred to as HFB1, was dimensioned anddetailed using a direct-displacement based design (DBD) method that was adopted inthe design of the PRESSS building (Priestley 2002). As a result, the dimensions of theprecast beams and columns and the hybrid frame connection details in the lower threefloors in HFB1 were identical to those used in the PRESSS test building. The secondbuilding, referred to as HFB2, was established using a force-based design method(FBD) in accordance with UBC 97 (1997). The design base shear of HFB1 was 132kips, which was 40 percent lower than the base shear of 220 kips obtained for HFB2.Hence, HFB1 and HFB2 were considered as two contrasting solutions for the designof the prototype building shown in Figure 1. Table 1 and Table 2 summarize themember dimensions and connection details derived for the hybrid frame buildings as447