| The research showed that the damage to the reinforced concrete structure or structure after fire can not be recovered due to the deterioration of the reinforced concrete material.If the structure of the building after the fire was slightly or moderately damaged need to be properly used,it must be properly repaired and reinforced.At present,the use of fiber reinforced plastic polymer(FRP)has been widely adopted due to its advantages of high strength and high efficiency,without increasing the weight of the structure,and construction convenience.Studies have shown that peeling failure due to insufficient bond strength between FRP and concrete was a common failure mode of FRP reinforced concrete.Hybrid bonding FRP(HB-FRP)using mechanical anchoring method can significantly improve the bonding performance between FRP and concrete,and improve the utilization of FRP.After the concrete was strengthened with HB-FRP,the interfacial bond properties and mechanism of FRP and concrete were studied:First of all,the concrete specimen was heated to a certain temperature.After being naturally cooled,FRP was adhered to the surface and mechanically anchored,and then the FRP-concrete bond slip test was performed.The parameters studied include: concrete exposure to fire(room temperature,100?,200?,300?,400? and500?),number of FRP adhesive layers(1,2 and 3),number of mechanical anchors(1,2and 3).The specific conclusions are as follows:1.The failure modes of concrete specimens reinforced with a-type HB-FRP(double-screw,gasket size 110mm×30mm×4mm)are FRP breaking,FRP peeling and bolt shearing.The failure modes of concrete specimens reinforced with b-type HB-FRP(single screw,gasket size 30mm×30mm×2mm)have tearing peeling of FRP,FRP pull off.When FRP is attached to one layer,with the increase in the number of mechanical anchorage,the ultimate bond load of a-type reinforced specimens is 1.19 times,1.61 times,and 1.23 times higher than that of b-type.2.The ultimate bond load of HB-FRP reinforced concrete specimens is 1.35-2.87 times larger than that of EB-FRP,and the strain value of each FRP measurement point is significantly greater than that of EB-FRP.For instance,the strain value of the specimenHB-H3N3C1 at the loading end is 2.86 times that of the specimen EB-H3C1,indicating that the HB-FRP reinforcement technology can more effectively improve the utilization of FRP.3.With EB-FRP reinforced specimens,the ultimate bond load increases with the increase of the number of FRP adhesive layers: The ultimate bond load of two-layer FRP bonded to concrete at room temperature,100?,200?,300?,400?,and 500? is 1.35 times,1.35 times,1.33 times,1.35 times,1.06 times and 1.35 times higher than that of pasting one layer of FRP,the ultimate bond load of three-layer FRP bonded to concrete is1.16 times,1.36 times,1.19 times,1.25 times,1.46 times,and 1.12 times higher than that of the two-layer FRP bonded to concrete.With HB-FRP reinforced specimens,the ultimate bond load increases with the increase of the number of FRP adhesive layers.However,with the increase of temperature of concrete exposed to fire,the ultimate bond load decreases slightly with the increase in the number of FRP adhesive layers at individual temperatures:the ultimate bond load of two-layer FRP bonded to concrete at room temperature,100?,200?,300?,and 400? is increased by 1.23,1.15,0.98,1.60,and 1.08 times,respectively,compared with the adhesion of one-layer FRP.The ultimate bond load of the three-layer FRP paste is about 1.23,1.20,1.43,0.98,1.16 times higher than that of the two-layer FRP,respectively.4.With HB-FRP reinforced specimens,the ultimate bond load increases with the number of mechanical anchors.However,with the increase in the temperature of concrete exposed to fire and the number of FRP adhesive layers,the ultimate bond load of individual specimens decreases slightly with the increase in the number of mechanical anchors:When FRP is attached to one layer,the concrete is at room temperature,100??200??300??400?,the ultimate bond load with two mechanical anchorages is increased by 1.08,1.10,1.09,1.04,and 1.27 times,respectively,compared with the use of a mechanical anchor.When the concrete is at room temperature,100??200??300?,the ultimate bond load with three mechanical anchorages is increased by 1.26,1.17,1.15,and 1.39 times,respectively,compared with the use of two mechanical anchorages.When FRP is attached to two layers,the concrete is at room temperature,100? ?200??300??400?,the ultimate bond load with two mechanical anchorages is increased by 1.04,1.07,1.12,1.29,and 1.38 times,respectively,compared with the use of a mechanical anchor.When the concrete is at room temperature,100??200??300?,the ultimate bond load with three mechanical anchorages is increased by 1.19,1.10,0.98,and0.89 times,respectively,compared with the use of two mechanical anchorages.5.With the specimens reinforced with EB-FRP,compared with concrete specimens at room temperature,as the temperature of the concrete increases,the ultimate bond load of the specimens increases.When the concrete is subjected to a fire temperature of 400°C,thelargest increase.For specimens with HB-FRP reinforcement technology,when the temperature of the concrete exposed to fire is less than 400?,the ultimate bond load fluctuates up and down with an increase in the temperature of the fire,and the variation range is small.The ultimate bond load when the concrete is subjected to a fire temperature of 400?is significantly higher than at room temperature:When installing two mechanical anchors,sticking one layer of FRP,and when the concrete is subjected to fire at temperatures of 100?,200?,300?,and 400?,the ultimate bond load is increased by 1.02 times,1.06 times,0.88 times,and 1.34 times respectively than at room temperature.When sticking two layers of FRP,and when the concrete is subjected to fire at temperatures of 100?,200?,300?,and 400?,the ultimate bond load is increased by 0.96 times,0.84 times,1.15 times,and 1.18 times respectively than at room temperature.When sticking three layers of FRP,and when the concrete is subjected to fire at temperatures of 100?,200?,300?,and 400?,the ultimate bond load is increased by0.93 times,0.99 times,0.92 times,and 1.11 times respectively than at room temperature. |
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