Seismic Behavior And Design Method Of Concrete Shear Wall With CFRP Grids

Traditional reinforced concrete（RC）shear walls will be crushed and spalled under the effect of medium and large earthquakes and the reinforcement will suffer buckling under pressure,resulting in large residual deformation of the shear walls.It will make the postearthquake repair and reinforcement of shear walls difficult and costly.Carbon fiber composite（CFRP）grid has the characteristics of light weight,high strength,and linear elasticity,while the grid form has bi-directional force capacity,good integrity,and anchorage.To improve the mechanical performance of concrete shear wall,CFRP grid is applied in the key position of the wall instead of steel bars.In this paper,a systematic study on the seismic performance and design methods of configured CFRP grid reinforced concrete shear walls is carried out through a combination of experimental studies,numerical simulations,and theoretical analysis.The main contents and results are as follows:（1）13 pieces of concrete shear walls with CFRP grids and steel bars were tested until failure under cyclic loading.Through analyzing the failure characteristics of specimens,the seismic performance of concrete shear walls under different shear span ratios and reinforcement configurations is studied.The load transferring mechanism and failure mechanism of specimen under different failure modes are revealed.As for the specimens with different shear span ratios,CFRP grid can effectively limit the crack width and make the crack distribution more uniform and denser.Moreover,horizontalil laid CFRP grid can significantly confine concrete and enhance its compressive strength and ultimate deformation capacity in the core area.Therefore,compared with RC specimens,specimens with CFRP grids have higher ultimate loading capacity and greater lateral deformation.Due to the linear elasticity and lower elastic modulus of CFRP grid,the residual deformation of shear walls with CFRP grids is lower than that of RC specimens,which has better self-reset performance.Moreover,the stiffness degradation rate of such specimens is lower,and secondary stiffness is reflected for specimens with large shear spans.（2）When the shear span ratio of concrete shear wall with CFRP grids is no more than 1.5,the shear effect is significant during loading.The SFI-MVLEM model considering the flexureshear coupling can better reflect the mechanical properties of the specimen.The peak load and its corresponding displacement are more accurate.When the shear span ratio of the shear wall with CFRP grids is greater than 1.5,the flexure effect is dominant during loading,and the shear effect is not significant.The MVLEM model can be used to simulate the hysteresis curve,initial stiffness,loading capacity and residual deformation of the specimen.Moreover,when the axial compression ratio increases within a certain radius,the loading capacity of the concrete shear wall can be effectively improved.However,when the axial compression ratio exceeds the range,the loading capacity of the specimens shows a downward trend,which is not conducive to the improvement of the mechanical properties.The variation of the axial compression ratio has a greater effect on the specimens with relatively small shear spans.（3）Based on the truss-arch model,the mechanical model of concrete shear wall with CFRP grids has a clear concept,which can accurately calculate the shear loading capacity of the shear wall under the consideration of axial compression.The coefficient of variation is 0.1861.Based on the section analysis method,the mechanical model of concrete shear wall with CFRP grids is established.The mechanical characteristics of the specimens are considered.The theoretical value of flexural bearing capacity is in good agreement with the experimental results,and the coefficient of variation is 0.1536.Based on the USFM model,a method for calculating the deformation of concrete shear walls with CFRP grids is established.Considering the deformation characteristics of the shear walls under the complex axial,flexural and shear stress,the deformation of the shear walls is divided into flexural shear deformation and slip deformation.The skeleton curve obtained by theoretical calculation is slightly larger than the experimental result,and the overall trend is in good agreement with the experimental result.Thus,the load-displacement curve of shear wall can be calculated more accurately.