Research On High Temperature Mechanical Properties Of PF-FRP Bars

Fiber Reinforced Polymer(FRP)has excellent properties such as light weight,high strength,and corrosion resistance.Therefore,it is gradually replacing steel materials and is widely used in the field of civil engineering.FRP tendons are also used for their excellent tensile properties and can replace steel bars.Become a hot research topic.FRP bars are mainly used as reinforcement bars for new structures or embedded reinforcement bars in concrete components.However,as an important material for the synthesis of FRP ribs,the resin matrix is very sensitive to high temperature.The commonly used resin matrix has a low glass transition temperature,which greatly reduces the mechanical properties of FRP ribs at high temperatures and restricts the promotion of FRP ribs.In order to fundamentally solve the problem of poor mechanical properties of FRP bars at high temperatures,a new type of high-temperature resistant phenolic resin basalt composite bar(BFRP)was prepared in this paper,and in order to make full use of the high temperature resistance of phenolic resin-based FRP reinforced bars,Tested the thermal insulation performance of alkali-activated cementitious materials,alumina cement cementitious materials,grouting materials,ECC-type cementitious materials,and several inorganic slot filling materials in which silica aerogel was added to the above-mentioned cementitious materials.,And applied it to the embedded reinforced FRP bar concrete unidirectional slab.Through experimental analysis,the fire resistance performance of the PF-FRP bar embedded reinforced mixed reinforced concrete unidirectional slab was studied.FRP reinforcement of the high temperature mechanical improvement of concrete structures is the key to solving the bottleneck problem of FRP reinforcement in civil engineering structures.The main work of this paper is as follows:1.Carry out the experimental research on the tensile strength of the new PF-BFRP bar in different high temperature conditions,and compare the tensile properties of the V-BFRP bar and the PF-GFRP bar at high temperature.The test results prove that phenolic resin and basalt fiber can work well together,and the mechanical properties of PF-BFRP tendons at high temperatures are the most superior.2.Carry out the experimental research on the compressive strength of six high-temperature resistant inorganic cementitious materials,alumina cement cementitious materials,alkali-activated cementitious materials,ECC cementitious materials,and inorganic cementitious materials added with silica aerogel.,By comparing the compressive strength and compression failure form,summarize the force characteristics of the cementitious materials used in the test,and provide a basis for subsequent research.3.Simulate the working conditions of embedded reinforced concrete with FRP bars,and use PF-BFRP bars with a cementitious material thickness of 25 mm as the standard production component,and develop the above six high temperature resistant inorganic cementitious materials coated PF-BFRP bar specimens The mechanical properties at high temperature are studied and compared with the specimens made of ordinary mortar,the specimens with a thickness of 5mm overlying cementitious material,and the specimens made of V-BFRP tendons.The test results prove that the high-temperature resistant cementitious material on the FRP tendon can greatly slow down the degradation of the mechanical properties of the FRP tendon at high temperature.The alumina cement cementitious material has the best thermal insulation effect,and the thermal insulation effect of aerogel is significant.The thickness of the coated cementitious material can delay the decrease of the mechanical properties of FRP ribs at high temperatures.4.Carry out PF-BFRP bar embedded reinforcement mixed reinforced concrete unidirectional slab bending test at room temperature,and compared with the commonly used V-BFRP bar reinforced mixed reinforced concrete unidirectional slab,in which the non-anchored areas of the reinforcement bars are used respectively Alkali-activated cementitious materials,alumina cement cementitious materials,grouting materials,ECC type cementitious materials,and alkali-activated cementitious materials added with silica aerogel are used for slot reinforcement.The normal temperature bending test results of the unidirectional slab show that the FRP embedded reinforced mixed reinforced concrete slab has low rigidity and high ductility.The FRP embedded reinforced mixed reinforced concrete slab has a three-stage bending process.PF-BFRP and V-BFRP There is little difference in the mechanical properties of embedded reinforced mixed reinforced slabs.PF-BFRP bars can replace the commonly used V-BFRP bars as new reinforcements or reinforcement bars for component stress.Several cementitious materials can be used as embedded The binder in the non-anchored area of the reinforcing bar is matched with the planting glue in the anchoring area,and works in coordination with the FRP reinforcing bar and the reinforcing plate.5.Carry out PF-BFRP bar embedded reinforced mixed reinforced concrete unidirectional slab fire resistance test,and compared with the commonly used V-BFRP bar embedded reinforced mixed reinforced concrete slab.The fire test results of the one-way slab found that the bottom reinforcement of the FRP embedded reinforced hybrid reinforced slab in the fire is higher than the upper reinforcement,and the PF-BFRP reinforcement and the reinforced slab have less mechanical performance loss under fire.The 25 mm thick high temperature resistant cementitious material can keep the BFRP ribs in the plate at a relatively low temperature field,thereby increasing the possibility of continuous holding force of the plate members in a fire.Using alumina cementing material as the slotting material to reinforce the concrete unidirectional slab can reduce the heat transfer rate.Using ECC type cementing material as the slotting material to reinforce the concrete unidirectional slab can increase the residual strength of the FRP ribs.Use aerogel-containing glue Condensing material or grouting material can improve the high temperature resistance of the board from the above two aspects.6.Based on ABAQUS software to carry out finite element analysis and research,consider the thermal properties of various materials,simulate the fire temperature field of the test board,and compare the calculation results with the test results,and find that the finite element simulation results are more consistent with the test results.