Study On The Effect Of High Temperature On The Mechanical Properties Of Grouted Sleeve Connection

Prefabricated concrete(PC)structure is one of the main structural styles in the process of building industrialization,and become more and more common in our country.However,the frequency of fire increases year by year,which will reduce structural performance and even cause structure collapse.The grouted sleeve connection(GSC)is one of the reliable and widely used reinforcement connections in prefabricated concrete structure,the connection’s performance will directly affect performance of the PC structure,so it is necessary to study the high temperature performance of GSC.At present,the high temperature performance of GSC is mainly studied based on uniaxial tension.However,GSC affected by high temperature may encounter cyclic loading,and the performance of GSC at this time may be different from that of uniaxial tension.Meanwhile,there are few mathematical models to predict the mechanical properties of GSC affected by high temperature under uniaxial tension,and even less considering cyclic loading.In order to provide reference for fire resistance design and post fire safety evaluation of PC structure,it is necessary to study GSC affected by high temperature under cycle loading,and establish mathematical models with some reliability on the basis of this test and existing tests,which can predict the mechanical properties of GSC affected by high temperature under uniaxial tension and cyclic load.In view of this,18 full grouted sleeve connections were made and were water cooled after high temperature,and then subjected to cycle loading at large strain.Based on the experimental results,there are several findings as follows: The GSCs occur rebar tension fracture after the temperature lower than 400°C and bond failure after the temperature higher than 400°C;There are two failure modes when the temperature is 400°C,but the main failure mode is bond failure;Cycle loading will promote the occurrence of bond failure on the basis of high temperature;As the number of cycles increases,the high temperature performance of GSC decreases,and this phenomenon becomes more obvious with the increase of temperature;After1000°C,the maximum load at the cycle stage may be higher than that at the end of the cycle.Based on this test and the previous tests,the mathematical models were established,which can predict the high temperature performance of GSCs under uniaxial tension and cycle loading.There are several findings as follows: The stress-strain curve of GSC affected by high temperature under uniaxial tension and cycle loading can be simplified as a two line model.The test parameters of each article are different,and some parameters will have a non-ignorable influence on the high temperature performance of GSC,so the differences of these parameters should be simply reflected in the corresponding mathematical models.The mathematical formulas for calculating the strength of GSC affected by high temperature under uniaxial tension and cycle loading with 50% and 95% guarantee rates were established,and the mathematical formulas for calculating the average value of elastic modulus and ultimate strain were established;The mechanical properties of GSC affected by high temperature under cycle loading are worse than those under uniaxial tension.