Analytical Investigation on the Seismic Performance of Partially Prestressed Concrete Beam-column Joints
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Date
2021-05
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Addis Ababa University
Abstract
Prestressed concrete concept was initially established to develop the performance of concrete members under flexure. But nowadays researchers are pointing out its satisfactory performance under seismic action. In this study, the seismic performance of partially prestressed concrete (PPC) exterior and interior beam-column joint (BCJ) is evaluated. Joint specimens are taken from a published experimental research program executed in Kyoto and Chiba University, Japan. Both joint types are subjected to a reverse cyclic loading at the beam ends and are designed to fail in shear at the joints. A 2D finite element software program, VecTor2, is used to validate the non-linear response of the joints. A total of three interior joint specimens and one exterior joint specimen with variable prestress have been validated. The software sufficiently captured the response of the PPC interior BCJs. While in the exterior BCJ, the software’s capability in capturing the last cycle after peak response was questionable. Six PPC exterior BCJs with variable prestress levels and four PPC interior BCJs with variable column axial load ratio has been analyzed and assessed for further investigation of its performance. The hysteretic response of the PPC exterior BCJ specimens is evaluated based on the ultimate storey shear capacity, stiffness, ductility, strength degradation, energy absorption, and dissipation capacity. Furthermore, the premature failure, and pinching of the PPC interior BCJ specimens, subjected to high compressive stress from column axial load and prestressing force is studied. In the PPC exterior BCJs, Variation of prestressing force didn’t encounter a significant effect on the ultimate shear capacity of the joints. Stiffness, and ductility increased significantly with prestressing force level before remarkable shear crack formation and prestress loss at the joint. Strength degradation was severe with the prestressing level. This phenomenon undermined the inelastic energy dissipation capacity of the highly prestressed joints at the later cycles. Since the software’s capacity is questionable at the last loading cycles, further evaluation of results at this loading stages might be crucial to obtain a more reasonable value. The column axial load variation in the PPC interior BCJ resulted in a considerable effect on the pinching behavior. Premature failure due to concrete crushing at the joint was not observed in any of the specimens.
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Keywords
Partially prestressed concrete, Beam-column joint, Prestress level, Column axial load ratio, VecTor2, hysteretic response, Storey shear capacity, Stiffness, Ductility, Strength degradation, Pinching, Energy absorption, dissipation capacity