Experimental Study On Seismic Behavior Of Solid Brick Masonry Walls Strengthened With Mortar Replacement

In the existing historical buildings,there are many phenomena that the strength of mortar decreases while the brick still has high strength,resulting in the bearing capacity of masonry wall not meeting the requirements.Based on the principle of "minimum intervention" in historical buildings,the research group puts forward a new method of masonry reinforcement.By replacing part of the old mortar with high-performance mortar,the masonry strength can be improved and the structural safety can be further improved.Based on the previous research,this paper designed 15 groups of quasi-static tests to study the influence of mortar replacement on the seismic performance of solid brick masonry wall.The wall test is divided into five series,considering the reinforcement form,aspect ratios,vertical compressive stress,masonry method,whether to open windows or not.The test results show that the replacement mortar reinforcement method is suitable for masonry structures in different states,and can effectively improve the cracking load and ultimate bearing capacity of the wall replacement area.For 225mm thick masonry wall,the depth of replacement mortar is 40mm,and the full replacement is the best,the X-shaped replacement is the second,and the double vertical replacement is the least.The replacement of mortar improves the overall stiffness and strength of the wall,changes the path of crack development,changes the failure mode from cross crack failure to through joint failure at the bottom,and increases the bearing capacity by 13.59-15.76%.The additional steel plate net can not improve the bearing capacity,but can effectively improve the ductility.With the decrease of the aspect ratio,the failure along the horizontal through joint is less likely to occur,and the effect of mortar replacement is better.With the increase of vertical compressive stress,the form of wall cracks also changes with the increase of vertical compressive stress,so the bearing capacity shows a gradient rising trend,and the effect of mortar replacement is better.For the walls with different masonry methods,the replacement mortar can play a reinforcing role,and the bearing capacity can be increased by 10-20%.This method can strengthen the wall with window opening,but it should pay attention to the reinforcement of four corners of the opening.The nonlinear analysis of the wall before and after reinforcement is carried out by ANSYS software.It is proved that the constitutive relation of masonry changes and the internal stress concentration area changes after mortar replacement,so the horizontal crack through failure occurs,which is consistent with the test results.Based on the influence factors and theoretical discussion and analysis of the shear strength of masonry,for the masonry of clay mortar,the recommended formula(6.21)is used to calculate the compressive strength of clay mortar masonry and determine the value of μ,and then the shear strength is calculated in combination with the masonry code formula;for the test wall strengthened by replacement mortar,it is recommended to calculate the clay mortar and replacement cement separately.The shear strength of mortar masonry is calculated by superposition of replacement proportion.