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This paper presents the shake-table tests and numerical analysis of a self-centering prestressed concrete (SCPC) frame to evaluate its seismic performance. The SCPC frame uses unbonded post-tensioned (PT) beam-column and column-foundation connections to provide the re-centering capability. Web friction devices are used at the beam ends to provide the adjustable energy dissipation capacity. A 0.5-scale, one-by-two bay, two-story specimen frame was designed and tested on a shake table under various ground motions with increasing intensities. The test results indicate that the SCPC frame had satisfactory seismic performance, and a desirable re-centering capability was observed with little structural damage even under severe earthquakes. An analytical model of the SCPC frame was also developed using the Open System for Earthquake Engineering Simulation (OpenSees) to replicate the test results. Good correlation is observed between the analytical and test results, indicating that the proposed model can be used to study the behavior of such self-centering (SC) structures.
Keywords: concrete frame; numerical simulation; post-tensioning; seismic performance; self-centering; shake-table test.
INTRODUCTION
Current design philosophy for traditional monolithic reinforced concrete (RC) moment-resisting frames (MRFs) in high-seismic regions aims to ensure that the frames are ductile systems and should not collapse under major earthquakes. However, significant structural damage and residual drifts due to inelastic deformations developed in beams and columns may result in substantial costs associated with damage repair and loss of building occupancy or operation after earthquakes.1 As a consequence, research efforts have been aligned at developing structural systems in which structural damage is minimized or avoided while preservation of life safety is maintained. Self-centering (SC) systems2 have shown promise of fulfilling this dual objective.
During the past decades, SC RC frames have been developed as an alternative to traditional RC frames. Early versions of SC concrete frames were introduced based on "hybrid connections" under the PREcast Seismic Structural Systems (PRESSS) Research Program.3,4 In these jointed hybrid solutions, precast concrete beam and column were assembled through unbonded post-tensioning techniques, and mild steel bars were grouted in ducts across beam-tocolumn joints. The "hybrid system" combined the SC properties of unbonded post-tensioning along with energy dissipation characteristics provided by yielding of mild steel. Subsequent research in hybrid precast connections proposed other means of energy dissipaters, including tension-only mild steel devices,5 external mounted mild...