Experimental Study On Mechanical Properties Of High Temperature Concrete

This thesis focuses on the high temperature damage of concrete, discussed themechanical properties deterioration mechanism and law of concrete under the high andlow temperature freeze thaw cycle, high temperature–holding time coupling effect ofand the action of high temperature cycle, and than establish the axial compressionstochastic damage constitutive model of the concrete after exposed to high temperature.Based on the axial compression stochastic damage constitutive model, this thesiscalculates the failure probability of concrete column exposed to different hightemperature.The building under high temperature because of bearing material failure thancollapse, resulting in casualties and economic loss. As the main load-bearing material,the research on mechanical property deterioration regularity and mechanism of concreteunder high temperature is particularly important. The concrete always work in acomplex environment. Therefore, this thesis mainly studys from the followingaspects:(1) Concrete of old building often work with crack, this thesis studys on thedeterioration mechanism and law of concrete containing macro crack under high andlow temperature freeze thaw cycle in the large range of temperature area.Theexperiment show that the mechanical properties of concrete decrease with the number ofhigh and low temperature freeze thaw cycle times increasing; And macroscopic crackintensify the damage of concrete under high and low temperature freeze thaw cycle, Themore crack concrete containning,the more high and low temperature freeze thaw cycledeterioration effect on the concrete.(2) The experimental studies on the mechanical properties of concrete afterdifferent high-temperature and different holding time were conducted, The influence ofthe different temperatures, different holding time on compressive strength, elasticmodulus, stress-strain curve of concrete was analyzed. The regularity and mechanism ofcompressive strength, elastic modulus, stress-strain curve of concrete affected bydifferent high temperature and different holding time was analyzed.(3) In the metallurgical plant, thermal power plant chimneys, and other specialconstruction, equipment, concrete often bears the long-term high temperature cycles,therefore, this thesis explores mechanical properties of concrete under different hightemperature cycles. (4) As multi phase composites, concrete contains a large number of crack afterhigh temperature, inevitably resulting in the mechanical properties of concrete withrandom. Based on the series parallel shear element model to simulate the mesostructureof concrete, with Weibull distribution description of micro unit failure regularity, andestablish stochastic damage constitutive model of concrete after high temperature; andthrough the fitting of experimental data of the Weibull statistical parameters, thusvalidating the paper constitutive model.(5) for engineering structure component, due to its own or external factors onconstruction and using process, effect on structure load, component production size,material properties are uncertain. Therefore, this thesis introduces stochastic damageconstitutive model, explores the concrete component size and load statistical rule,analysis failure probability of high temperature injury concrete column under the axialpressure.Based on the experiment results, summed up the deterioration law of concreteunder high and low temperature freeze thaw cycles, different temperature and differentholding time and different high temperature cycles.Then establish the compressionstochastic damage constitutive model of concrete after high temperature, and applied tofailure probability analysis of structural. In this thesis, the mechanical properties ofconcrete after high temperature has important guiding role to post-disaster constructionidentification, assessment.