The Effect Of Restrained Condition On Concrete Temperature Deformation And Temperature Stress

Thermal stress is an important structural load, sometimes even becomes a key factor leading to crack or damage in the course of structural running. The e environment temperature of the vast majority concrete buildings is alternating, and the effect of temperature stress is unavoidable. Based on the importance of concrete thermal stress analysis and determination, while there is a big difference between the calculated and measured values of concrete thermal stress, in this paper,the experimental method was designed to directly measure the thermal stress and temperature deformation of concrete specimens. By comparing the measured results and calculations results of temperature deformation and temperature stress, the relationship between the concrete temperature deformation and temperature stress was studied; explore the influence of various factors on the analysis of concrete temperature deformation and temperature stress.Experimental results show that, with the approximate same temperature change, the temperature deformation of the concrete specimen is closely related to its initial stress state; the greater the initial stress, the stronger restriction effect on the test piece subjected, and the smaller the temperatur es deformation. According to the issues that the measured temperature stress is less than the calculation temperature stress, the following several aspects were discussed:First, the elasticity theory formula of the calculating temperature stress was simply derivedSecond, the change of the elastic modulus of concrete varying with temperature that ranges by(20 ~ 70?) is negligible, and this rule was verified by test results.Third, the mechanism of thermal expansion of concrete under compression state was discussed. At First, the mechanism of thermal expansion of homogeneous materials under compression state was discussed, on the basis of this, the concrete material has own unique deformation law. Next, the temperature deformation of the steel pipe under the compressed state was verified by the test, it was confirmed the fact that under pressure state the temperature deformation of steel pipe was less than the free state, while in a compressed state,the decrease degree of the temperature deformation of the steel pipe is far smaller than concrete specimens.Fourth, on the base of analysis and study of existing research results and the experimental phenomena, that temperature deformation of steel pipes and concrete specimens is less than the amount of theoretical calculations, the law of the temperature deformation of the concrete specimen under the compressed state was analyzed, the new concept "concrete temperature deformation coe fficient ?" was proposed, and the relationship between the concrete temperature deformation coefficient ? with the initial stress of the concrete was obtained by the temperature theoretical formula stress inversion analysis.Through these analysis and disc ussions, in practical engineering, when the thermal stress of structure or component was calculated, the stress state should be considered on the temperature deformation properties of concrete.