| Ultra-high Performance Concrete(UHPC),which has excellent physical and mechanical properties and durability,is used as the bonding medium of the bonding anchorage system.It can effectively anch or Carbon fiber reinforced polymer(CFRP)cables with significant anisotropy.For this reason,this paper relies on the National Natural Science Foundation of China "Research on the fire resistance of carbon fiber prestressed cable-bonded anchorage system infused with activated powder concrete(51908206)",and the fire resistance and fire resistance of CFRP single-strand cable-bonded anchorage system are investigated.The experimental research and theoretical analysis of the residual anchoring performance a fter high temperature provide a theoretical basis for the compilation of the fire resistance design specification and the fire identification standard of the CFRP cable and its anchoring system.The main research contents and conclusions of this paper are as follows:(1)The experimental study on the axial tensile performance of UHPC at high temperature was carried out,and the influence of treatment temperature,volume dosage of steel fiber and other parameters on the axial tensile performance and rupture performance of UHPC at high temperature was revealed.The axial tensile constitutive model suitable for UHPC at high temperature was established.The results show that the addition of steel fiber can improve the high temperature burst resistance of UHPC.The axial tension property of UHPC decreased rapidly with the increase of treatment temperature and increases with the increase of steel fiber volume content.The UHPC high temperature axial tension constitutive model established in this paper has high precision.(2)The pull-out test with and without initial tension and fire resistance test of CFRP single tendon cable bonded anchorage system at high temperature were carried out,the influence rules of initial tension ratio and bonding length on the high temperature anchorage performance,fire resistance limit and failure temperature of CFRP single tendon cable bonded anchorage system were revealed,and the influence mechanism of temperature load path on the anchorage performance of bonded anchorage system was clarified.The practical calculation formulas of interfacial bonding strength,critical anchorage length and fire resistance limit of bonded anchorage system at high temperature were established.The results show that when the treatment temperature increases fro m 25℃ to 400℃,the interfacial bonding strength of CFRP reinforcement UHPC decreased approximately linearly at first and then decreased slowly.The fire resistance limit and failure temperature of bonded anchorage system decreased with the increase of init ial tension ratio.The existence of initial tension leaded to greater attenuation of anchorage performance of bonded anchorage system at high temperature.The above practical calculation formula has high accuracy.(3)In order to study the relaxation and creep properties of CFRP single-bar cable bonded anchorage system at high temperature,the relaxation and creep tests of 24 groups of anchorage performance specimens were carried out under constant temperature rise and constant load.Based on the test results,the influence laws of key parameters on the anchoring force loss and interface slip of bonded anchorage system at high temperature were clarified,the change laws of residual anchorage performance of bonded anchorage system after high temperature relaxatio n and high temperature creep were revealed,and the high temperature relaxation and creep model suitable for CFRP single tendon cable bonded anchorage system was established.A model suitable for characterizing the relationship between anchorage stress los s rate and interface slip rate of bonded anchorage system in steady state was established.(4)In order to study the residual anchorage performance of CFRP single tendon cable bonded anchorage system after high temperature,the pull-out tests of 8 groups of anchorage performance specimens undergoing heating and cooling process under dead load were carried out.Based on the test results,the effects of treatment temperature,initial tension ratio and bonding length on the residual anchorage performance of bonded anchorage system were revealed,and a practical calculation method suitable for the interface bonding strength of bonded anchorage system of CFRP single tendon cable after high temperature was established.Combined with the research results of anchorage performance of bonded anchorage system under high temperature,a characterization model suitable for the recovery law of anchorage performance after high temperature was established. |
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