| The coupling beams in reinforced concrete coupled shear wall and wall frame are key components to assure seismic behavior of commonly used structural system in tall building. The small span-to-depth ratio coupling beams usually used in engineer are required have high shear to compress ratio and high ductility ratio. However, to the present day an effective design scheme easily implemented in engineer for this type member haven't been found over the world. On base of seismic behavior analysis and compound force response analysis under shear-bending moment cyclic loads in reinforced concrete members, the small span-to-depth ratio synthetically reinforced coupling beams in which diagonal reinforcement and rhombic reinforcement are taken as main shear resistance reinforcement was put forward by the paper. Series of experiments including 29 specimens confirmed that this scheme coupling beam can get no less than 4.0 and 4.5 chord rotation ductility and a good energy dissipation capacity at condition of 0.25~0.30 shear to compress ratio.The main diagonal strut-tie model, rhombic reinforcement truss model and stirrup truss model which working together in shear-bending moment resistance mechanism are also presented based on research of the experiment specimen's behavior. And cooperative working analysis method of these models is founded after the coupling beam's shear-bending moment integral deformation compatibility equation was successfully met. Verification shows that the analysis model is in good agreement with experiment at aspects of predicting reinforcement and concrete stress state when non-elastic cyclic deformation happened after the specimen yield. Lateral deformation and axial direction deformation of the coupling beams are also predicted accurately. The research adds a successful explorative achievement for application of strut-tie model on the statically indeterminate and low cyclic loading condition in which field academic circles has just begun to study over the world.According to the fact that analysis basis was insufficient when the seismic measures for high seismic rate RC coupled shear wall structure were worked out, the paper designed multi-stories(20~25 stories) frame shear wall typical structures accordance with Chinese code strictly for the first time. And the member as coupling beam type's chord rotation ductility demand level under the rare seismic was preliminary got by nonlinear dynamic response analysis at input of multi-seismic waves. After exploration for the coupling beam's ductility ability and demand ratio which is different from frame beam, on premise of regardless of coupling beam's stiffness and force adjustment, taking 3.5~4.0 chord rotation ductility demand as goal, regarding span to depth L/h≤3.5 as scope of small span to depth ratio coupling beam's definition, based on a series of seismic behavior experiment results of 29 synthetically reinforced coupling beams, 8 diagonally crossing reinforced coupling beams and 6 conventionally reinforced coupling beams, and using the other experiment results of above mentioned the later two kinds reinforcement scheme coupling beams, a full set of high ductility small span-to-depth ratio coupling beam's design suggestions which be applied correspondingly in the former 3 reinforced scheme at condition of shear to compression less than 0.30,0.20 and 0.12 were brought forward. It provides reference for revising of Chinese Code for Seismic Design of Building and Technical Specification for Concrete Structures of Tall Building.
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