Experimental Research On Seismic Behavior Of Diagonally Reinforced Concrete Coupling Beams

Coupling beam connects shear walls and consumes energy,as the key member of the coupled shear wall,which has important influence on seismic performance of the shear wall system.Reinforced concrete diagonal reinforced coupling beams are commonly used in small span-depth ratio to solve the problem of premature brittle failure in traditional coupling beams.Diagonal reinforced coupling beams can be reinforced by confinement of individual diagonals or full confinement of diagonally reinforced.Because existing research results are relatively few and have some problems,the equivalence of two reinforcement arrangements of diagonal reinforced coupling beams lacks systematic and reliable experimental data support.Chinese code(GB 50010-2010)and American code(ACI 318-19)have made provisions for reinforcement arrangements of full confinement of diagonally reinforced,but some national codes do not explicitly accept this reinforcement arrangements.In addition,many test devices do not constraint the axial restraint.and there is no exact conclusion about force mechanism and deformation capacity of diagonal reinforced coupling beam.Therefore,on basis of existing research results,this paper adopts the form of single-storey coupled shear wall to designed and completed six reinforced concrete diagonal reinforced coupling beams test with cyclic loading.Span-depth ratio(1.0,1.75,2.5)and reinforcement arrangement(confinement of individual diagonals or full confinement of diagonally reinforced)were major test variables.This paper mainly studies primary factors affecting bearing capacity and deformation capacity of diagonal reinforced coupling beams,verifies the equivalence of two reinforcement arrangements in conditions of large shear-compression ration,and evaluates the rationality of the allowable value of shear capacity in Chinese code.The results show that two reinforcement arrangements of diagonal reinforced coupling beams have little difference in bearing capacity and deformation capacity under the same span-depth ratio,and the two reinforcement arrangements are equivalent.The span-depth ratio significantly affect the failure mode and deformation capacity of diagonal reinforced coupling beams.The Coupling beam’s failure mode in large span-depth ratio is bending failure,which ductility is good.In small span-depth ratio,the failure mode of coupling beam is shear failure,and the ductility of coupling beam is difficult to achieve the fourth or fifth performance standards specified in code of JGJ 3-2010.The critical span-depth ratio of the two failure modes can be 1.75.In addition,this paper proposes corresponding shear capacity models for whether coupling beams have axial restraint.The shear capacity model is verified by this test and the collected test data at home and abroad.The verification results show that the calculation model can well reflect the characteristic of shear capacity of diagonal reinforced coupling beams.Axial constraints makes the shear capacity of coupling beams increase by about 50% average.On this basis,this paper proposes a recommended formula for shear capacity of diagonal reinforced coupling beams.Compared with the standard formula,the recommended formula can better reflect the real mechanism of diagonally reinforced coupling beams,and the fitting degree is greater and safer.The main factors affecting stress performance and deformation performance of diagonal reinforced coupling beams are analyzed.The results show that span-depth ratio and shear compression ration will affect the deformation capacity of diagonal reinforced coupling beams.Span-to-depth ratio positively influence specimen’s rotation,and shear compression negatively influence specimen’s rotation.