Study On Optimization Design For A Wedge Anchor Of FRP Tendon Based On Homologous Materials And Its Performance

Steel corrosion is a common phenomenon in traditional reinforced concrete structures.The use of corrosion-resistant fiber reinforced composites(FRP)is an effective method to solve the above problems.At present,a lot of FRP tension/cable demonstration projects have been built at home and abroad.However,CFRP can not work together well.due to the high price,small ductility,and large the thermal expansion coefficient with concrete,The corrosion resistance of glass fiber reinforced composite(GFRP)bars is poor,and the relaxation rate of aramid fiber reinforced composite(AFRP)bars is too large.These factors limit its widespread use in prestressed structures.With the development of new materials,in recent years,basalt fiber reinforced composite(BFRP)has become a hope for replacing prestressed steel bars for use in engineering structures due to its superior mechanical properties,high cost performance,corrosion resistance,and fatigue resistance.However,due to the material characteristics of the Anisotropy of the BFRP tendon,its transverse compressive strength and shear resistance are low,so that it can not be anchored by traditional anchoring methods.This is also one of the key factors that can not be widely used at present.Therefore,the key of BFRP tendons used as prestressed tendons is to develop a safe and reliable special Anchorage and design a new type of Anchorage system for anchoring BFRP tendons.In this paper,the optimization design and performance of BFRP tendons homologous material wedge anchorages are studied from three levels: finite element analysis,BFRP tendons and different forms of anchorages.The static,fatigue and creep properties of the whole Anchorage system of BFRP tendons were studied.The research provides a basis for the application of BFRP Anchorage system in engineering.The main research contents and results are as follows :(1)Finite element simulation analysis of BFRP tendon Anchorage system.Through the study on the Anchorage length,inner cone angle,varying stiffness of load transfer medium,different Anchorage forms,etc.of BFRP tendon homologous composite material were analyzed.The influence trend of the parameters on the Anchorage system of BFRP tendon was obtained.The optimal design strength control value of Anchorage system is determined by testing the basic mechanical properties of BFRP tendons and the compressive strength of load transfer medium.The three-stage variable stiffness Anchorage is finally determined.(2)Experimental study on the static properties of the wedge Anchorage system of homologous composite material of BFRP tendon.The Anchorage performance of the whole system can be determined based on the ultimate load and failure modes of Anchorage system under staticload,the relationship of load-slip between single tendons and Anchorage in Anchorage area,and the stress distribution.The static Anchorage efficiency of the new BFRP Anchorage system is 88.5%,and the BFRP Anchorage efficiency coefficient is 80%.Although both are less than the specified values,the new BFRP Anchorage system is optimized for this load transfer medium splint because of the traditional steel Anchorage.At the same time,the stress distribution of BFRP bar surface in Anchorage area was obtainedby the finite element model.A new model is provided for the finite element simulation of BFRP tendons Anchorage system.(3)Experimental study on fatigue performance of BFRP tendon homologous composite wedge Anchorage system.The fatigue life and damage evolution of the BFRP tendon composite wedge Anchorage system under different fatigue load conditions(stress amplitude,stress ratio,frequency,etc.)are studied,and the S-N curve of the BFRP tendon composite wedge Anchorage system is given.A model for predicting fatigue strength is established.The prestress loss mechanism can be evaluated according to the following up of the clamp and the slip of the BFRP tendons,which can provide a solution for the long-term performance of the BFRP tendons Anchorage system.(4)Experimental study on creep properties of BFRP tendon homologous composite wedge Anchorage system.By testing the following up of BFRP tendon slip and clamp in Anchorage area,the prestress loss mechanism can be evaluated,and the solution for the long-term performance of BFRP tendons Anchorage system can be provided.Three groups of different stress level creep tests,through the strain time curve,demonstrated the two stages before creep,analyzed the creep damage of the BFRP tendon composite wedge anchor system,measured the creep residual strength,and passed the BFRP bond anchor system.The residual strength was improved.Further research on creep properties of the new BFRP tendon Anchorage system is provided.