| In recent years,under the influence of environment,disaster and function change,the reinforcement and maintenance of infrastructure has become a research hotspot in the structure field of civil engineering.As a new type of structural reinforcement material,Fibre Reinforced Polymer(FRP)has attracted much attention due to its lighter quality,high strength,high corrosion resistance and ease for construction,FRP strengthening technology is also widely used in engineering practice.A specific form of FRP used for flexural reinforcement of concrete structures is cutting grooves along the length of the beam in the concrete layer,and then embedding the FRP strip into the grooves with adhesive(Near-Surface Mounted,NSM),The foundation and key of this reinforcement method is the bond behavior of FRP and concrete,however,the method of embedding the strip is still immature and has some shortcomings.The anchorage with reliable performance is designed in this paper,the bond and anchorage behavior of specimens of Near-Surface Mounted CFRP with adhesive,specimens of Near-Surface Mounted CFRP with anchorage and specimens of Near-Surface Mounted CFRP with both adhesive and anchorage were investigated by single shear test.The test variables include concrete strength anchor diameter,anchor number,and anchor spacing et al,The main contents include:(1)The pressure test for the designed anchor is complete and the relation between torque and stress is established;the pull-out force test for single anchor is complete,the calculation formula of ultimate load of CFRP strip and concrete is established.(2)The influence of concrete strength on the bond behavior of NSM CFRP strip embedded with adhesive and concrete with was studied,it is found that the ultimate load and stiffness of specimens will be increased with the increase of concrete strength.At the same time,the failure mode changed from debonding failure in adhesive-strip interface to the rupture of the strip,after analysis strain distribution and bond slip relationship,it is found that the local bond stress reaches the limit and debond,and then continue to transfer to the free end,until all strip debond or reach the tensile strength of the CFRP strip,the bond-slip model is established.(3)The anchorage behavior of NSM CFRP strip embedded with anchor and concrete is studied,it is found that the main failure mode are the relative slip failure of anchor sawtooth and CFRP strip and the rupture of the strip,anchorage behavior is not affected by concrete strength and anchorage spacing,The anchorage behavior is better when increasing the bolttorque within the acceptable torque range,using more anchorages and larger anchorage.Based on the test results,the anchorage ultimate load formula is put forward,the anchor stress slip model is established.(4)Predict the ultimate load of the single shear test of NSM CFRP strip embedded with both adhesive and anchor specimens and complete the test,it is found that the ultimate load can be increased with the increase of concrete strength and anchor size,the main failure mode is the rupture of CFRP strip,after analysis strain distribution and bond slip relationship,it is found that the adhesive debond and the anchorage slip from the loaded end to the free end,the bond-slip model is established.(5)Three kinds of concrete reinforcement methods with NSM CFRP strip are compared,a nd the ultimate load,stress slip model and construction difficulty are compared,it is found that the performance of the anchor is reliable,The stress-slip model of specimen which using strip embedded with anchor is simple and accurate,and it’s construction and designed difficulty is、、are less difficult. |
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