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

The opening masonry wall structure has a single force transmission path and poor integrity.Compared with the frame structure and the shear wall structure,it lacks multiple seismic defense lines and has been seriously damaged in previous earthquake disasters.Due to the poor seismic performance of masonry structure,with the development of China’s construction industry,masonry structure is no longer used as the main structural form in high-rise buildings.However,due to historical reasons,there are still a large number of masonry structures in small and medium-sized cities and towns in China.Demolition and reconstruction is not in line with reality and will waste a lot of human and material resources.Based on the detailed introduction of the earthquake damage mechanism and common failure modes of open masonry walls,this article aims at constructing multiple anti-seismic defense lines and improving energy dissipation capacity,starting from the perspective of improving the horizontal bearing capacity and deformation capacity of open masonry walls,Respectively proposed the double-sided Modified Reactive Powder Concrete(MRPC)surface reinforcement and the MRPC surface reinforcement of the window wall..Through the quasi-static test and Simulation of the wall with the height width ratio of three sides of 1:1 and the mortar strength of M2.0,the failure mode,bearing capacity,stiffness,energy consumption and other seismic indexes of the wall under different reinforcement forms are analyzed(1)Based on the concept of RPC and ultrafine particle dense system,the role of each matrix material and the best mixing ratio are introduced.According to the different elastic modulus and mechanical properties of steel fiber and polypropylene fiber,considering the fiber hybrid effect,the strengthening and toughening mechanism and appropriate mixing amount of two kinds of fiber materials at different stages and levels of crack development are analyzed The results show that the adhesive free layer has good fluidity,good adhesive strength,and good fluidity.(2)The results show that the bonding strength between MRPC and the wall is good.The double-sided MRPC surface layer reinforcement and the window wall MRPC surface layer reinforcement of masonry wall with openings can effectively inhibit the development of cracks,improve the bearing capacity and energy consumption of the wall,and significantly improve the seismic performance of the wall.(3)The double-sided MRPC surface layer reinforcement of the open masonry wall has a significant effect on cracks in the small deformation stage,significantly improves the integrity of the open masonry wall,and greatly improves the bearing capacity,rigidity and energy consumption of the wall.Compared with the reinforced masonry wall with openings,the peak bearing capacity of the double-sided MRPC surface layer reinforced specimens is increased by about 159%,the ductility coefficient is increased by about 242%,the ultimate displacement angle is increased by about 8%,and the cumulative energy consumption is increased by about 615%.The seismic capacity of the wall is improved,and the limit displacement angle is increased to a small extent.Combined with the analysis of experimental phenomena,the double-sided MRPC reinforcement method does not significantly improve the deformation capacity of the wall,and it still has certain brittle failure characteristics in the form of failure.(4)The MRPC surface layer reinforcement form of the wall between the windows does not significantly suppress the cracks in the small deformation stage of the lower wall of the open masonry wall.Compared with the unreinforced specimens,the peak bearing capacity is increased by about 95%,the ductility coefficient is increased by about 71%,and the ultimate displacement angle It is increased by about 91%,and the cumulative energy consumption is increased by about579%,which greatly improves the deformation capacity and energy consumption capacity of the wall.Combined with the analysis of the test phenomenon,the wall between the windows did not appear obvious damage during the test,and the typical X-shear oblique cracks appeared in the wall under the windows,which changed the failure mode of the open masonry wall under pseudo-static force,and changed from brittle failure to brittle failure.For ductile failure,multiple seismic defense lines are constructed through reinforcement,which meets the three-level seismic fortification target proposed by my country.(5)Through the finite element software OPENSEES,the whole continuity model in the refined model is selected,and the fiber element method is used to simulate the three walls respectively.The simulation results are in good agreement with the experimental bearing capacity,unloading stiffness and displacement,which proves the feasibility of OPENSEES to simulate the seismic performance of masonry structures.