Experimental Research On Connection Performance Of Restraint Grouting-anchoring Overlap-joint Of Steel Bar In High Temperature

The structure form of prefabricated buildings has been developed rapidly and vigorously promoted in our country with its advantages of high efficiency,convenience,energy-saving and environmental protection.The safety and integrity of precast concrete structures are guaranteed by reliable connections between the components,and restraint grouting-anchoring overlap-joint of steel bar method is one of the key technologies of rebar connection in precast concrete structures.Nowadays,the study on the mechanical properties of the restraint grouting-anchoring overlap-joint of steel bar is almost concentrated in the normal temperature environment,while the experimental researches of the connection at high temperature have not been conducted.In this paper,the experimental study on the mechanical properties of restraint grouting-anchoring overlap-joint of steel bar at high temperatures was carried out,and the ultimate bearing capacity,anchoring performance and failure mode of the specimens were analyzed.On the basis of experimental research,considering the interaction between various components,finite element software ABAQUS was used to simulate the unidirectional tensile of specimens under high temperature,and the influence law of different temperatures and rebar diameter on the connection performance was obtained.The specific work carried out is as follows:(1)The unidirectional tensile of specimens with two diameters of rebar and 1.0 times of basic anchorage length under high temperature which includes from room temperature to 600 degree centigrade,a total of 6 temperatures,was carried out.There are 3 parallel specimens in each group,with a total of 36 specimens.(2)The failure mode and the load-displacement curve of the specimens were obtained in the experimental process.On the basis of primary data,the ultimate bearing capacity,anchoring performance and bond strength in the elastic phase are further analyzed.(3)In combination with the failure phenomena and failure modes of the specimens at each temperature,the conclusions were drawn: finally,the steel bar of the specimens almost snapped off.In the range of room temperature to moderate temperature,the ultimate bearing capacity of specimens decreased less,while at high temperatures,the carrying capacity of specimens reduced greatly,it could be reduced to 40% of the ultimate bearing capacity at normal temperature.At the same temperature,the influence of different diameters of steel bar on the failure mode of specimens tended to be consistent.(4)ABAQUS finite element analysis software was used to simulate the unidirectional tensile of specimens in high temperature,and the bonding effect was realized by nonlinear spring.By comparison,the simulation results were in good agreement with the test results,which can provide references for further analysis of connection performance at high temperature.