Research On Analysis And Evaluation Method Of Seismic Performance Of Masonry Reinforced By PP-Bands

There are a large number of masonry buildings in rural areas of China.The building material of brick-concrete masonry structure is brittle,and its weak shear capacity and flexural capacity determine its vulnerability under the action of horizontal seismic forces.Given the generally poor seismic performance of the rural masonry structures,the cheap,effective and easy construction polypropylene band(PP-band)reinforcement method provides a new idea for reinforcing rural masonry buildings.At present,there is no in-depth research on the PP-band reinforcement method at home and abroad.Therefore,a series of quasi-static tests,bending tensile tests and numerical simulation analysis have been carried out in this paper to further explore the impact of the PP-band reinforcement on the shear behavior,flexural behavior,and seismic capacity of masonry structures.The specific research works are as follows:(1)We have carried out quasi-static tests for two PP-band reinforced masonry walls and two comparative masonry walls.We have mainly studied the influence of PP-band and the different compressive strength of plastering mortar on the failure pattern,ultimate bearing capacity,hysteresis curve,stiffness degradation,energy dissipation capacity of the masonry wall.The tests results show that the PP-band can effectively improve the ultimate bearing capacity and ultimate displacement of the masonry wall,the cracking phenomenon and stiffness degradation are also been delayed.The ultimate bearing capacity,energy dissipation capacity and displacement ductility of the PP-band reinforced wall are increased by 48%,47%and 226%.(2)Bending tensile tests were carried out on the masonry specimens,which include 108 straight joints specimens and 108 gear joints specimens.The influences of the PP-band,different strength of plastering mortar,different strength of masonry mortar and the effects of different mesh size of PP-band on the flexural behavior of the masonry structure are mainly studied.The tests results show that the strength of masonry mortar has the greatest influence on the flexural mechanical properties of masonry structures,but the strength of high-strength plaster mortar has no significant effect on the flexural strength of unreinforced specimens.For reinforcement of PP-band specimen,reinforcement of PP-band can improve the flexural bearing capacity of the specimens,the higher the strength of plaster mortar,the better the reinforcement effect.The main purpose of the PP-band is to constraint the specimen to prevent sudden breaks of the specimen due to brittle fracture.The smaller the PP-band mesh size,the better the reinforcement effect,and the ductility of the unreinforced specimen is increased by dozens of times.(3)Based on the bending tensile test results,the Abaqus finite element software was used to establish the separate finite element models.The numerical simulation results were compared with the test results to verify the reliability of the model.Finally,the parametric analysis was carried out to futher verify the effectiveness of the PP-band reinforcement to the bending resistance performance of the masonry structure.(4)Based on the Pushover method and the Abaqus finite element software,a simple and effective method is explored to evaluate the seismic performance of the masonry structure.Firstly,two masonry buildings with actual earthquake damage were used as research objects.Abaqus software was used to establish a three-dimensional finite element model and Pushover analysis was also performed.By comparing the actual seismic damage with dynamic time history analysis results,the feasibility of the Pushover method for evaluating the seismic performance of masonry structures was verified.Then,choosing a single-story masonry building as the object to further study the influence of the PP-band on the seismic performance of the masonry structure.The results show that under frequent earthquakes and fortified earthquakes with basic fortification intensity,the inter-layer displacement angle of the PP-band reinforced structure is reduced.PP-band plays a certain role but its enhancement effect is not obvious;however,under severe earthquakes,PP-band has played a significant role,and the seismic performance of the structure has been significantly enhanced.