12.07.2015 Views

Report - PEER - University of California, Berkeley

Report - PEER - University of California, Berkeley

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PERFORMANCE-BASED SEISMIC ASSESSMENT OF TWOPRECAST CONCRETE HYBRID FRAME BUILDINGSSri SRITHARAN 1 and Ataur RAHMAN 2ABSTRACTThe application <strong>of</strong> precast concrete hybrid frames has gained popularity in high seismic regionsdue to their unique features, which include minimum structural damage when subjected toearthquake loading and the re-centering capability. The hybrid frame that utilizes acombination <strong>of</strong> mild steel reinforcement and unbonded prestressing to connect precast beamsand columns has been implemented in a few structures in high seismic regions <strong>of</strong> the UnitedStates. This frame was also one <strong>of</strong> the four jointed frames included in a large-scale five-storybuilding test conducted as part <strong>of</strong> the PRESSS (PREcast Seismic Structural System) program.The use <strong>of</strong> mild steel and prestressing steel at the connections reduces the hysteresis energydissipating ability <strong>of</strong> the frame when compared to an equivalent monolithic concrete frame.Utilizing the test results obtained from the PRESSS building to validate the analytical modelsand defining acceptance criteria based on transient and residual inter-story frame drifts, thispaper presents a multiple-level performance-based assessment <strong>of</strong> two five-story precast hybridframe buildings. Based on the prototype building from the PRESSS program, the analyticalinvestigation was conducted at a 60 percent scale so that a direct comparison between theanalytical results and PRESSS test data would be possible.Keywords: Precast; Concrete; Hybrid frame; Performance-based; Seismic; Assessment.1.1 Framing Concept1. INTRODUCTIONThe hybrid framing concept is used to establish moment-resisting frames from singlebayprecast concrete beams and multi-story high precast concrete columns. Figure 1shows typical details <strong>of</strong> a hybrid frame, in which the beams and column are connectedusing unbonded post-tensioning tendons and mild steel reinforcement across theprecast interfaces at the mid-height and closer to the top and bottom surfaces <strong>of</strong> thebeams, respectively. Prior to post-tensioning, the interfaces and ducts housing the1 Assistant Pr<strong>of</strong>essor, Department <strong>of</strong> Civil, Construction and Environmental Engineering, Iowa State<strong>University</strong>, Ames, IA 50011, USA2 Graduate Research Assistant, Department <strong>of</strong> Civil, Construction and Environmental Engineering, IowaState <strong>University</strong>, Ames, IA 50011, USA445

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