Study On The Influence Of Erosion Environment On The Bonding Properties Of FRP Sheet Reinforced Blocks

Due to the low cost of masonry and the convenience of materials,masonry materials are widely used in the houses of villages and towns in China,including some masonry buildings with historical value.These old buildings after many years of use,bearing capacity and seismic capacity are greatly reduced,in order to safety needs,the masonry structure repair and reinforcement has been impatient.In recent years,fiber reinforced composite(FRP)has emerged at home and abroad to provide a new direction for masonry structure reinforcement with its advantages of light weight,high strength,good durability,convenient construction and so on.Scholars at home and abroad of FRP strengthened masonry structure interface bond properties are a lot of research results,but FRP and masonry structure of the durability of the bonding interface under erosion environment and the degradation mechanism of very few,so for the research of FRP reinforced masonry structure interface bond properties,has important theoretical significance and engineering significance.The interface adhesion between FRP and masonry block under the action of temperature,freeze-thaw cycle and immersion in water was studied by single shear test.Temperature including room temperature(25 ℃ or so)test and high and low temperature(20℃ and 40℃ and 60℃ environment conditions respectively placed 7days,15 days)test,has completed the seven batch test;The freeze-thaw cycle test was designed for 15 times and 30 times,and two batches of tests were completed.The immersion test was designed to last for 30 days,60 days,90 days and 365 days respectively.Three batches of tests were completed,among which the samples placed in the water for 365 days were still in the erosion environment,and the test was not taken out until the specified planned time was reached..The main research contents and conclusions are as follows:1.The failure modes and bonding properties of the specimens at different temperatures were compared.At room temperature,the damage position of the specimen was all on the fiber sheet,and the fiber sheet was torn and damaged.40℃environment conditions have less effect on the specimen failure modes;60 ℃environment conditions on the carbon fiber reinforced clay brick and the destruction of the carbon fiber sheet reinforcing shale brick specimens form most affected,change the failure position of part of the specimen in the bonding interface,place the longer,the more interface failure of specimen;-20℃ destroy of environment conditions onthe interface is bigger also,some specimen damage location in the bonding interface.Room temperature environment under the condition of limit load of the specimens,compared to 20 ℃ condition limit load of the specimens to reduce the most,next60℃,40℃ minimal impact,with the increase of placing time,the greater the extent of the ultimate load,the specimens reduce 20.63% at most.2.The failure modes and bonding properties of samples under freeze-thaw cycle were compared.After 15 times of freeze-thaw cycle and 30 times of freeze-thaw cycle,there were two interface failures in each specimen.After 30 times of freeze-thaw cycle,the clay bricks of the two specimens were damaged,and the rest of the specimens were damaged on the fiber sheet.Compared with the ultimate load of specimens at room temperature,with the increase of the number of freeze-thaw cycles,the ultimate load of specimens decreases by 53.89% at most.3.The failure modes and bonding properties of the specimens under immersion condition were compared.The failure forms of specimens soaked in water for 30 days,60 days and 90 days were all fiber sheet tearing failure without interface failure.Compared with the ultimate load of the specimen at room temperature,with the increase in the number of days of immersion,the degree of reduction is greater,and the maximum reduction is 46%.4.Through ABAQUS simulation,the bond performance of FRP sheet reinforced block is analyzed,and the interface of reinforced specimen is simulated with spring element SPRING2.The simulated finite element results of ultimate load,force-slip curve,maximum strain and stress distribution are in good agreement with the test data.The effects of bond length,bond width of FRP sheet and block strength on the bond strength of the specimens were also analyzed.