Seismic Test Study On Short-span Coupling Beams With Synthetical Diagonal Reinforcement And Design Advise

Coupling beams combining two coupled walls of RC high-rise structures not only influence the lateral stiffness of the coupled walls, the moment to axial force ratio and the moment to shear ratio of the single wall by span-to-depth ratio, but also are the primarily energy dissipating elements in the coupled walls under severe earthquake. Coupling beams play a key role in improving seismic resistance behavior. According to the practical structure, small-span-to-depth-ratio coupling beams are adopted in the design. It is proved by the test outcome in home and abroad that the shear failure happening early cannot be avoided and the ductility cannot be satisfied if the coupling beams are designed with the conventional method of frame beams. In recent years, the effective design method that small-span-to-depth-ratio coupling beams in coupled walls improve seismic resistance behavior is discussed in home and abroad. the advice on new reinforcement scheme of small-span-to-depth-ratio coupling beams, i.e. adding diagonal bars and rhombic inclined bars on the basis of traditional reinforcement(synthetical diagonal reinforcement coupling beam), have been given. By the experiment of 20 specimens with span-to-depth ratio of 0.8~2.5,well seismic resistance behavior and project applicability of new reinforcement scheme have been proved, In order to perfecting this research, the main study work of this thesis is as following :â‘ Because of the specimens with the span-to-depth ratio beyond 2.0 are few. so complete 3 tests of synthetical diagonal reinforcement coupling beams with span-to-depth ratio of 2.0~2.5 under low-cyclic repeated loads in order to research:1) Seismic resistance behavior of coupling beams with new reinforcement scheme.2) Research proper proportion between diagonal reinforcement (including rhombic reinforcement) and stirrups.â‘¡Complete a conventional reinforcement scheme of coupling beams with span-to-depth ratio of 3.0 under low-cyclic repeated loads,the test objective is to research the seismic resistance behavior of conventional reinforcement scheme of coupling beams with relative higher shear-compression ratio.â‘¢Because the author of the dissertation engaged in the work of the full set of design suggestion about seismic resistance small-span-to-depth-ratio coupling beams in coupled walls which submitted to recension group of Code for design of concrete structures generalized by Pro.Fu JianPing and Dr.Pi TianXiang ,so in the conclusion chapter simply introduce the core contents of the design suggestion, in the giving scope of application of small-span-to-depth-ratio coupling beams according to the shear-compression ratio from high to low use the syntheses diagonal reinforcement coupling beams,diagonal reinforcement coupling beams and conventional reinforcement coupling beams relatively.On the basis of the research completed, it is proved that:â‘ Synthetical diagonal reinforcement coupling beams with span-to-depth ratio of 2.0~2.5 still acquire well seismic resistance behavior (displacement ductility stably achieve 4.0~6.0) and project applicability.â‘¡The test of conventional reinforcement scheme of coupling beams with span-to-depth ratio of 3.0 and with shear-compression ratio of 2.0 perform well seismic resistance behavior, the displacement ductility is 3.8.â‘¢The full set of design suggestion about seismic resistance small-span-to-depth-ratio coupling beams in coupled walls can be referenced in the next recension of Code for design of concrete structures.