Experimental Research On Connection Performance Of Restraint Grouting-Anchoring Overlap-Joint Of Steel Bar Under Cyclic Loading After High Temperature

Prefabricated structures have the advantages of high industrialization and convenient construction,and have broad application prospects.The restraint grouting-anchoring overlap-joint of steel bar is one of the main forms of reinforced connection in prefabricated concrete structures.Its performance after high temperature plays a decisive role in the safety of such structures after fire,and it is also the basis for the evaluation and reinforcement of structures after fire.It has important engineering application value to study the lap joint performance of reinforced concrete anchor after high temperature.In this paper,the experimental study of restraint grouting-anchoring overlap-joint of steel bar after high temperature under uniaxial tension and cyclic load is carried out,and the numerical simulation analysis of restraint grouting-anchoring overlap-joint of steel bar after high temperature is carried out by using finite element software.The main work is as follows:(1)Uniaxial tensile and cyclic loading tests were carried out on 54 specimens with diameters of 12 mm,14mm and 16 mm,which were heated to 200℃,300℃,400 ℃,500 ℃ and 600 ℃,respectively.Among them,there are 18 groups of specimens in uniaxial tensile test,with 1 specimen in each group;There are 18 groups of specimens in cyclic loading test,with 2 parallel specimens in each group.(2)Through tensile test,the load-displacement curve and failure mode of restraint grouting-anchoring overlap-joint of steel bar specimens were obtained,and the yield load,ultimate load,anchorage performance,average bond strength and ultimate displacement of restraint grouting-anchoring overlap-joint of steel bar specimens after high temperature were further analyzed.The results show that the failure mode of steel bar tensile fracture occurs in most specimens after high temperature;The ultimate bearing capacity of the specimen after natural cooling increases at medium and low temperature,while the bearing capacity of the specimen decreases at high temperature,and the lowest is 70% of normal temperature.After the same high temperature,the larger the diameter of the specimen,the easier it is to have bond-slip failure.(3)By comparing and analyzing the results of uniaxial tensile test and cyclic loading test,the influence of cyclic loading on restraint grouting-anchoring overlap-joint of steel bar specimens after high temperature is analyzed.The results show that the bond-slip failure mode occurs more frequently in cyclic specimens than in single tensile specimens.(4)The finite element software ABAQUS is used to simulate the restraint grouting-anchoring overlap-joint of steel bar after high temperature,and the nonlinear spring is used to simulate the bond-slip effect between reinforced concrete and grouting material.The comparison between simulation results and test data shows that the model can reflect the failure process of restraint grouting-anchoring overlap-joint of steel bar after high temperature and has good accuracy.