Abstract
In current structural design codes, elastic vibration modes are used for seismic design. However, when a structure is subjected to strong earthquakes and inelastic response or even when collapse damage is observed, the damage state is always unevenly distributed along the height of the structure. Such a phenomenon implies the materials of stories with elastic response and slight damage are not fully utilized. In this paper, a new practical and effective method, which improves collapse resistant capacity by making full use of materials, is proposed for reinforcement concrete (RC) frame structures at a structural collapse state. In this method, incremental dynamic analysis (IDA) is used to evaluate the structural collapse capacity. Tangent_ratio (TR) is formulated based on the IDA curves, and the longitudinal reinforcement of columns is modified based on the TR to achieve uniform distribution of damage along the height of building. Fewer variables are optimized and constraints of the provisions in current codes are considered, which makes the proposed procedure more computationally efficient and practical. The proposed method is employed on a 5-story RC frame structure to illustrate its feasibility and practicality. Comparison work indicates that the refined seismic design method can significantly increase the collapse resistant capacity and decrease the maximum inter-story drift ratio response under strong ground motion in a few iterative steps without a cost increase.
Highlights
A force-based method is adopted in current seismic design codes
Comparison work indicates that the refined seismic design method can significantly increase the collapse resistant capacity and decrease the maximum inter-story drift ratio response under strong ground motion in a few iterative steps without a cost increase
The efficiency and implementation of the proposed method are demonstrated by optimizing a five-story reinforcement concrete (RC) frame structure design
Summary
A force-based method is adopted in current seismic design codes. It regards the earthquake loads as equivalent lateral inertia force consistent with the fundamental elastic vibration modes of structures [1,2,3,4]. Li [34] proposed an analytical formula of the lateral load pattern for multi-story buildings to increase the collapse resistant capacity It showed that the optimized lateral load pattern leads to lower collapse probability than that of the conventional seismic design method with the same construction cost. Various studies were conducted on the optimum seismic design by optimizing the cross section of the structural elements considering inelastic performance under severe earthquakes [35,36,37]. Though new lateral load pattern oriented research works can be nested in the seismic design procedure in current codes, the adopted lumped mass finite element model cannot accurately predict the strong nonlinear response under severe earthquake ground motion, and cannot catch the element damage without consideration of the constrained provisions in codes (e.g., minimum and maximum reinforcement ratio, strong column and weak beametc). The efficiency and implementation of the proposed method are demonstrated by optimizing a five-story RC frame structure design
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