Research On Seismic Behavior And Shear Capacity Of Diagonally Reinforced Fiber-reinforced Concrete Coupling Beams With Small Span-to-Depth Ratio

Coupling beams with small span-to-depth ratio is the important component of shear wall structures of the tall building,the scholars at home and abroad have studied on the seismic performance of coupling beams with small span-to-depth ratio through changing reinforcement schemes,span-to-depth ratio and matrix materials.Our research group has conducted the experimental study on the seismic performance of diagonally reinforced fiber-reinforced concrete(FRC)coupling beams with small span-to-depth ratio.The results show that this kind of coupling beams has higher bearing capacity and deformation capacity.But it was found that deformation capacity of coupling beams decreased due to the yielding outward on compression of the diagonal reinforcement in the test.Based on above,this paper proposes an improvement scheme that adding lacing wire in diagonal bars,the research contents and results are as follows:(1)When the section size and reinforcements of the FRC coupling beams were basically the same,the lacing wire was added in the diagonal bars and three diagonally reinforced FRC coupling beam specimens with small span-to-depth ratio were designed and tested under reversed cyclic lateral loading.Then,the failure mechanism,hysteresis energy dissipation,deformation performance,stiffness and strength degradation of the coupling beams were analyzed.The results show that the lacing wire in diagonal bars can prevent the diagonal bars yielding outward on compression,which brings out the change in the failure type of coupling beams with small span-to-depth ratio from brittle shear failure to flexural shear failure.The hysteretic curves are fuller,the ductility and damage resistance have been improved obviously,and the strength and stiffness degradation are slow.(2)Based on the analysis of the experimental results,the shear mechanism and the calculation model of shear bearing capacity of coupling beams with small span-to-depth ratio,then the calculation formula of shear capacity was established,considering the contribution of FRC,diagonal bars and stirrups on the shear capacity of diagonally reinforced FRC coupling beams with small span-to-depth ratio.The results show that the calculating results of the shear capacity agree well with the experimental data.However,the reliability of the formula deserves further research because of the limited experimental data.