Research On The Temperature Stress And Crack Of Mass Concrete In Giant Column Of Super High-rise Building

The problem of concrete cracks has been concerned by the academia, especially for the mass concrete whose main cracks are caused by the temperature difference. Since the mass concrete has such characteristics as large volume, high hydration heat and poor thermal conductivity, which will make its deformation uncoordinated beause of internal and external self-restrain. When the temperature stress exceeds the tensile strength of concrete of the same age, the cracks of concrete is produced.There are two reasons leading to concrete cracks in mass concrete, they are concrete shrinkage and temperature respectively. The effect of shrinkage includes drying shrinkage and autogenous shrinkage, and the temperature effect which is caused by hydration heat of concrete will produce the temperature stress. Based on the above, the main contents are as follows:(1)Based on the existing theories of temperature damage for concrete, the variable of damage had been carried into the temperature stress analysis so that the concrete mechanical performance would be considered under the damage of materials.(2) Based on the analysis results of the early crack factor of concrete, a test was designed and performed to monitor the temperature and strain. The temperature points were arranged evenly on the plate to achieve the highest temperature during concrete pouring, the range of temperature, the surface temperature; A reasonable coefficient of linear expansion was obtained by the contrast under the equal condition and standard condition; Strain of the studs was monitored to provide the basis for the concrete temperature stress.(3)In view of the core section of the giant column, cracks were analysed and the proportion of temperature, shrinkage and difference in linear expansion coefficent had been separated. It can be concluded that the reasons leading to core concrete cracks development are 75% temperature and 25% concrete shrinkage separately. According to the different situation of concrete cracks, based on the material and constryction, several measures had been taken to prevent the concrete cracks generating this for kind of structure.(4) In view of the surface of the giant column, the total stress of concrete can use the effective temperature stress, line differential stress and shrinkage stress. It can be concluded that the reasons leading to the total stress are 65%~85% line differential stress and 35%~15% temperature stress, shrinkage stress.