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Title |
Seismic Behavior of Moment Frame Retrofitted by External Buttress-Type Structure according to In-Plane Stiffness of Concrete Diaphragm
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Authors |
강혜령(Hye-Ryeong Kang) ; 노정태(Jung-Tae Noh) ; 이상현(Sang-Hyun Lee) |
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DOI |
https://doi.org/10.4334/JKCI.2020.32.6.533 |
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Keywords |
외부보강공법; 강체격막; 반강체격막; 비선형 정적해석 external reinforced method; rigid diaphragm; semi-rigid diaphragm; nonlinear static analysis |
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Abstract |
The seismic reinforcement method that involves attaching a frame with high stiffness to the outside of an existing building yields a structure that is hard to consider as a perfectly integrated one. The assumption of slabs as rigid diaphragms could be used to differently evaluate the actual behavior of seismic reinforced structures. Therefore, this paper proposes a diaphragm modeling method that properly evaluates seismic reinforcement effects by comparing characteristics of building behavior according to the diaphragm assumption. The behavior of frames is analyzed according to the diaphragm modeling method, which uses rigid and semi-rigid elements. As a result, a moment frame with relatively even stiffness shows similar performance curves and results. The semi-rigid diaphragm of the moment frame with shear walls at both ends shows brittle behavior due to the shear failure of the center column, unlike the case of the rigid diaphragm. To evaluate the diaphragm effects for an actual building, a non-seismically designed school building extended by a concrete wall structure is considered by performing pushover analysis. Results show similar behavior characteristics regardless of type of diaphragm in the longitudinal direction. However, the semi-rigid diaphragm model in the transverse direction shows brittle behavior because of shear failure of columns at the end sides of the existing building. This failure is caused by the mode shape, in which the deformation at both ends is relatively large compared to the center due to the in-plane deformation of the slab. Therefore, if a high stiffness member is installed or reinforced in a part of building, the semi-rigid diaphragm model can be used to accurately evaluate the response of building.
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