Effects Of Horizontal Grouting Defects On The Mechanical Properties Of Grouted Sleeve Splice After Exposure To Elevated Temperature

Grouted sleeve splice has now developed into the main way of rebar connection in assembled concrete structures,and the excellent mechanical properties of grouted sleeve splice are the key to ensure the overall safety of assembled buildings.The existence of grouting defects during the construction process seriously affects the mechanical properties of the grouted sleeve splice.In addition,high temperature caused by building fire further degrades the mechanical properties of the grouted sleeve splice.Therefore,considering the effects of horizontal grouting defect categories,grouting defect rates,temperatures,rebar diameters and loading methods on the mechanical properties of grouted sleeve splice,the mechanical properties of grouted sleeve splice were tested and the effects of horizontal grouting defects on the mechanical properties of grouted sleeve splice after high temperature were analyzed.The main research contents and conclusions are as follows:(1)The effects of temperatures(100,200,300,400,500,600,700,and 800°C)on the thermal deformation properties of grouting material during the complete process of heating and cooling were studied.The results showed that the thermal deformation of grouting material could be divided into three stages: ascending stage,plateau stage and rapid ascending stage during the heating process.During the constant temperature process,the linear deformation rate and linear deformation coefficient of grouting material increased first and then decreased at 100～500°C,and the linear deformation rate and linear deformation coefficient of grouting material continued to increase with the increase of holding time at 600～800°C.At the end of cooling process,the residual deformation values of grouting material at 100°C～500°C were all negative and reached-403μm at 500°C,while residual deformation value at 600°C～800°C were all positive and reached 115μm at 800°C.(2)The effects of horizontal grouting defect categories(horizontal radial defects,denseness defects),grouting defect rates(0,10,15,20,25,and 30%)and temperatures(20,200,400,and 600°C)on mechanical properties of grouted sleeve splice with rebar diameter of 18 mm under uniaxial tensile loading were studied.The results showed that the failure mode of grouted sleeve splice was not significantly affected by grouting defect categories.The effects of temperature below 400°C on the mechanical properties of the splice were not significant.The mechanical properties of grouted sleeve splice were decreased significantly after the high temperature of 600°C,which could be reduced to 57.0% of that at room temperature.(3)The effects of rebar diameters(14,18,and 20 mm),grouting defect rates(0,10,20,and 30%)and temperatures(20,200,400,and 600°C)on mechanical properties of grouted sleeve splice with horizontal radial grouting defect under uniaxial tensile loading were studied.The results showed that with the increase of grouting defect rate and temperature,the failure mode of grouted sleeve splice changed from rebar fracture to pull-out of rebar.The larger the diameter of rebar,the more significant this effect was.The damage depth of grouting material of the splice with rebar diameters of 14,18 and 20 mm were 9.26,9.41 and 10.09 mm.(4)The effects of loading methods(uniaxial tensile loading,cycle loading at high stress),grouting defect rates(0,10,20,and 30%)and temperatures(20,200,400,and600°C)on mechanical properties of grouted sleeve splice with horizontal radial grouting defect were studied.The results showed that there were three failure modes of grouted sleeve splice: rebar tensile fracture,rebar pull-out after yielding and rebar pullout before yielding.Below the grouting defect rate of 10%,the loading method had no obvious effect on the ultimate strength of grouted sleeve splice after exposure to high temperature.When the grouting defect rate was not less than 20%,the ultimate strength loss of the grouted sleeve splice after high temperature under cyclic loading increased with the increase of temperature.After cyclic loading and 600°C,compared with uniaxial tensile loading,the ultimate strength of grouted sleeve splice with 20%grouting defect rate was reduced by 32.3%,while the difference in ultimate strength of the splice with 30% grouting defect rate was 10.6%.(5)Based on the test results,the finite element model of the grouted sleeve splice was established using ABAQUS,and the effects of grouting material strength(80,100,and 120MPa),grouting defect rate(0,10,20,and 30%)and temperature(20,200,400,and 600°C)on the mechanical properties of grouted sleeve splice were studied.The results showed that the little difference in the simulation and experimental results of the yield strength and ultimate strength of the grouted sleeve splice.The local effect of equivalent plastic strain of grouting material was related to the grouting defect rate.The increase in temperature led to extension and expansion of grout tensile damage and equivalent plastic strain to the interior of the reinforcement anchorage.(6)Based on the existing bond strength theory,the effects of grouting defect rate,rebar diameter,rebar anchorage length,grouting material compressive strength and sleeve restraint on the bond strength of rebar grouting material was considered,and a ultimate load calculation formula for grouted sleeve splice under uniaxial tensile loading was proposed.The minimum rebar anchorage length should not be less than 9times the diameter of rebar when pull-out failure of rebar occurs in the splice under 30%horizontal grout defect rate and room temperature.There are 127 figures,46 tables,and 150 references in the thesis.