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©2012 Civil-Comp Ltd |
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M. Valente
Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Milan, Italy
Keywords: dissipative bracing system, reinforced concrete frame, seismic retrofitting, displacement-based design procedure.
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reference
The study presented in this paper includes the results of numerical investigations carried out on a new dissipative bracing system for seismic retrofitting of reinforced concrete (RC) frames. The proposed system, called the braced ductile shear panel (BDSP) system, is composed of a ductile shear panel and concentric braces. Previous numerical investigations [1,2] show that the BDSP system provides high stiffness and presents excellent energy absorption capacity and stable hysteresis characteristics. It can be used as a primary lateral load resisting system for new or existing steel frames. The study investigates the likelihood of the application of the proposed dissipative bracing system to the case of non-ductile RC frames subjected to seismic excitation. A displacement-based design procedure was applied with the aim of enhancing the seismic performance of a non-ductile five-storey RC frame using braced ductile shear panels. The geometric dimensions of the BDSP system were taken as the primary design variables. The proper size of the BDSP system was determined in order to satisfy the desired displacement limit state of the frame. The size of the BDSP system in each storey was determined considering a distribution pattern proportional to storey shear. The storey-wise BDSP distribution pattern resulted in a fundamental design parameter in the procedure because it affected the values of the characteristics of the BDSP system throughout the frame. The procedure was able to satisfactorily achieve the target displacement and was validated with the results of nonlinear dynamic analyses. The favourable effects of the application of the dissipative bracing system on the seismic response of the multi-storey RC frame were assessed. The results of the numerical investigations showed that the proposed bracing system can protect the main structural elements of the frame preventing them from damage under severe seismic actions. A more uniform distribution of inter-storey drifts was registered for the retrofitted frame compared to the bare counterpart, avoiding the development of a soft-storey mechanism at the second level. The addition of the BDSP system reduced the energy dissipated by the primary structural elements of the frame, giving a significant contribution to the energy dissipation capacity of the whole system for severe seismic actions. The energy dissipation mostly concentrated in the dissipative steel panels, decreasing the maximum displacements of the retrofitted frame and the plastic demand on the structural elements.
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- 1
- M. Valente, D. Giannuzzi, R. Ballarini, A. Hucklebridge, "Braced ductile shear panel: a new seismic resistant framing system", Structural Engineer World Congress, Italy, 2011.
- 2
- M. Valente, D. Giannuzzi, R. Ballarini, A. Hucklebridge, "Numerical investigation on a new dissipative bracing system for steel structures", Eurosteel, Budapest, Hungary, 2011.
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