Research On Fire Resistance Of Precast Reinforced Concrete Structures With Rebar Spliced By Grout-filled Coupling Sleeves

In recent years,prefabricated concrete structure has become a new field of building struc-ture in China.The prefabricated concrete structural components are produced in the factory and assembled at the construction site,so the construction speed is obviously improved.Compared to traditional construction way,its management system is more scientific and the cost of efforts and resources are greatly reduced.Prefabricated Concrete Structure has developed rapidly in China.Steel sleeve grouting connection is widely used in prefabricated concrete structures,as its convenient operation and reliable connection.Resesrchers have studied the static and dynamic properties of grouting sleeve at normal temperature extensively.But there is few studies on mechanical properties of grouting sleeves under fire condition.Therefore,this thesis is to study the mechanical properties of steel sleeve grouting connection joint and the reinforced concrete structure with grouting sleeve in fire,mainly include the following:(1)The tensile properties of steel sleeve grouting joints under fire are studied systematically by means of numerical simulation,and the relationship between the fire resistance time and load ratio under the condition of high temperature are obtained.Firstly,the finite element model of grouting sleeve is simulated under normal temperature,the tensile bearing capacity that 64mm diameter sleeve and 25mm diameter steel bar make up the grouting joint is determined.Compared to tests results to determine the reliability of numerical simulations under normal temperature.Then the numerical simulation of the fire is carried out,and the fire resistance time load ratio curve is fitted by the analysis results.(2)Analysis of other types of steel sleeves structures coupling thermal is made.In this thesis,modified the relationship between the fire resistance time and load ratio cure,which is 64mm diameter sleeve and 25mm diameter steel bar grouting joint for summering the general relationship of engineering design.The fire resistance time and load ratio curve is obtained,which provides the basis for selecting the sleeve according to the design load size and fire resistance time.(3)In this thesis,we study the drawing slip from between the sleeve and the steel bar caused by the large deformation of the structure,considering the effect of temperature stress under the high temperature of fire,presenting a fiber beam element to calculate the thermal structure coupling of a reinforced concrete frame structure with a sleeve.We use the MATLAB language to develop the fiber beam theory.Then high temperature stress analysis of fire is compared with the calculation results of solid45 and solid70 elements,which has been conducted by the fiber beam element.In this thesis,the fiber beam element calculation programs consider the drawing slip effect between steel bar and sleeve,shorten the time of the finite element analysis of the precast concrete frame structure,and ensure the accuracy of the calculation results at the same time.This thesis provides a reference for the study of the fire resistance of the steel sleeve grouting connection,and also provides a more convenient method for finite element calculation of the fire resistance design on the prefabricated concrete structure.