Experimental Study On Seismic Behavior Of Masonry Walls With Low Strength Openings Strengthened By MRPC

Masonry structure has a long history of application in China,and still occupies an important proportion in the building structure.However,due to the long history of traditional masonry structure construction,nonstandard seismic structure design and the brittleness of masonry structure itself,the overall collapse of structure occurred in many earthquake disasters,resulting in serious economic losses and casualties.Therefore,it is of great significance to strengthen the old masonry structure and study its seismic performance.In this paper,the low-strength masonry wall with window openings is taken as the research object.Through quasi-static test and finite element software ABAQUS,the low-strength masonry wall specimens with openings under different reinforcement methods of modified reactive powder concrete(MRPC)surface are studied and analyzed,and the positive effect of MRPC surface on the seismic performance of masonry wall specimens is quantitatively studied.The main contents and conclusions are as follows.(1)The influences of water binder ratio,binder sand ratio,steel fiber content,water reducer content and mass ratio of silica fume and fly ash on fluidity,compressive strength and tensile strength of MRPC were determined by orthogonal test,and the influence order of established test factors was determined by range analysis.The results show that the water binder ratio and the binder sand ratio have great influence on the mechanical properties of MRPC under low temperature curing,and the water binder ratio plays a controlling role.According to the results of range analysis and the actual situation of test,the optimal mix proportion of MRPC with moderate strength,good plasticity and suitable for masonry wall plastering is prepared and applied to masonry wall reinforcement.(2)The masonry mortar with strength grade of M2.0 is used to simulate the old multi-storey masonry structure residence.Through the low cycle repeated tests of unreinforced masonry wall,MRPC single-sided reinforced masonry wall and MRPC double-sided reinforced masonry wall,the test phenomenon and the collected data are studied and analyzed.The test results show that: the MRPC surface layer has a significant positive effect on the seismic performance of masonry walls,the ultimate bearing capacity and displacement ductility coefficient of the single and double reinforced walls are increased by 86.07%,153.77%,8.91% and 133.46% respectively compared with the unreinforced walls,and the cumulative energy consumption of the single and double reinforced walls in failure state is increased by 342.11% and 643.34% respectively compared with the unreinforced walls The stiffness degradation rate of solid wall is the slowest.(3)By analyzing the data of steel strain and MRPC surface strain,it is found that MRPC surface can not only bear the vertical load and horizontal load,but also effectively restrain the occurrence and development of inclined cracks in the wall,and significantly improve the bearing capacity of masonry wall.(4)Based on ABAQUS,the nonlinear simulation analysis of the above three masonry walls is carried out.Through the equivalent plastic strain(PEEQ)nephogram and skeleton curve,it can be seen that the integral model can better reflect the crack distribution location,range and development trend of the specimen;due to the idealization of material constitutive,the limitation of finite element software itself and the construction quality in the test process,the model is not suitable There is still a difference between the simulation results and the test results,but the difference is within the acceptable range.