Experimental Study On Seismic Behavior Of Masonry Window Wall Substructure Strengthened With Steel Mesh Surface

Masonry structure in China has a long history of development,especially in rural areas where it is the primary construction method.However,with the development of our economy,masonry structures have gradually been replaced by other methods such as reinforced concrete.According to relevant statistics,houses built in the 1970 s and 1980 s are now considered ’aging’.Due to imbalanced economic development,most masonry houses in rural areas and small towns cannot be completely demolished.Therefore,reinforcing and renovating masonry structures is an urgent task.Previous research results have shown that effectively reinforcing masonry structures under rational damage modes can significantly improve their seismic resistance.However,there is currently a lack of theoretical analysis on calculating the seismic resistance of reinforced window sill walls under damaged conditions.Based on the rational damage mode of masonry structure window sill walls,this study analyzes the seismic performance of unreinforced and reinforced window sill wall substructures before and after reinforcement using pseudostatic tests and OpenSees finite element simulations considering different influencing factors.This provides a basis for calculating the seismic bearing capacity of damaged and re-reinforced window sill walls:(1)Design and manufacture the spandrel-substructure and carry out lowcycle reciprocating quasi-static test research,strengthen the damaged substructure with steel wire mesh surface mortar method and carry out quasi-static test,and carry out the seismic performance research of the strengthened spandrel-substructure.The test results show that the recovery degree of bearing capacity,deformation performance and energy consumption of each specimen have been improved to some extent after strengthening,and the seismic performance is good.After reinforcement,the failure mode of each specimen is changed from "failure mode between windows" to "failure mode under windows",which is more reasonable.(2)The finite element analysis software OpenSees is used to simulate the spandrelsubstructure before and after reinforcement,and the correctness and rationality of the finite element model are verified by comparing the simulation results with the experimental results.Aiming at the reinforced spandrel-substructure,the influence of different influencing factors on the seismic performance of the damaged and reinforced spandrel-substructure is analyzed by finite element software.The simulation results show that when the stiffness ratio is reduced or the span-height ratio is increased,the shear bearing capacity of the structure increases gradually,which has little effect on the displacement and ductility of the structure in each stage.When the axial force is increased,the shear bearing capacity of the structure increases slightly,but the displacement and ductility have no effect,which shows that the constraint ability provided by the axial force is limited.When the strength of mortar is increased or the density of steel mesh is configured,the shear bearing capacity of the structure increases obviously.However,increasing the mortar strength makes the limit and failure displacement decrease,and the ductility of the structure becomes worse,while increasing the density of steel mesh makes the ductility of the structure better.(3)According to the results of seismic performance test and numerical simulation analysis of the spandrel-substructure before and after reinforcement,the bearing capacity composition of the spandrel-substructure after reinforcement is analyzed,and the factors affecting its shear bearing capacity are taken into account,and a simplified calculation model of shear bearing capacity of the spandrel-substructure after reinforcement is put forward;Establish a formula for shear bearing capacity of that spandrel-substructure after reinforcement;The calculated value,experimental value and simulated value of shear bearing capacity of strengthened specimens are compared and analyzed.The results show that the error between the calculated bearing capacity of the spandrel-substructure under strengthened and the experimental and simulated values is within a reasonable range.The formula for calculating the shear bearing capacity of the spandrel-substructure after reinforcement is reliable.