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Title |
Analysis of Displacement-based Collapse Resistance for Vertical Irregular Buildings according to Column-end Rotation Constraints
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Authors |
정기혁(GiHyuk Jung) ; 최인섭(Insub Choi) ; 김준희(JunHee Kim) |
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DOI |
https://doi.org/10.4334/JKCI.2023.35.5.487 |
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Keywords |
수직비정형 건축물; 변위기반 붕괴저항성; 층간변위비; 회전제약; 부재력 vertical irregular structure; displacement-based collapse resistance; interstory drift ratio; rotation constraint; member force |
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Abstract |
The term “collapse resistance” refers to a structure’s ability to withstand external forces until it collapses. During the Pohang earthquake, seismic damage predominantly occurred at the columns of vertical irregular buildings (i.e., piloti-type structures), specifically those with a soft story. Piloti-type structures often exhibit smaller displacement-based limit states (i.e., interstory drift ratio [IDR]) compared to single lateral load-resisting systems, since displacement and force tend to be concentrated at the soft first-story during earthquake excitation. However, a quantitative assessment of displacement and member forces concerning collapse levels in piloti-type structures has not been conducted. In this study, the collapse resistance of piloti-type structures was analyzed, focusing on member forces and displacements. The member forces and displacements were analyzed using an idealized frame model, where the flexural stiffness of the horizontal member connected to the columns is replaced by the rotational stiffness of the column ends. The collapse resistance of the piloti-type structures was analyzed based on the IDR limit state, employing nonlinear static analysis for 2D numerical models. For the first-story columns, the shear forces in piloti-type structures were calculated to be up to 1.93 times greater than those in moment frames. Consequently, the displacement-based collapse resistance of piloti-type structures was determined to be 47 % lower than that of shear-dominant RC shear wall systems conforming to current seismic performance evaluation guidelines. Therefore, to prevent overestimating the seismic performance of piloti-type structures, the displacement-based limit states for piloti-type structures should be set lower than those of the shear-dominant RC shear wall systems.
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