Alpine Region Of Mass Effects Of The Concrete Surface Thermal Simulation Studies

The mass concrete structures are applied more and more abroad in engineering project, the problem of the crack which is caused by temperature change is puzzled people always. In the winter negative temperature season or suddenly confronted cold wave, the concrete surface temperature gradient is precipitous, so concrete surface cracks occurs when the tension stress of concrete surface overrun, especially in the early-age of concrete the tensile strength is low and the crack easily occurs. Laying certain thickness heated board can reduce the concrete surface tension stress effectively to prevent crack. So researching the heat preservation effect of concrete surface heated board is significative.In this article according to finite element computational theory of mass concrete temperature field and temperature stress field, based on large general-purpose software ANSYS, using APDL language to design the simulation calculation program of roller compacted concrete gravity dam temperature field and temperature stress field in construction stage and during operation period. During preparation period of this program, we consider the effectiveness of stratified pouring,construction interval,the change of modulus of elasticity,the adiabatic rise of temperature,the change of ambient temperature,concrete creep,the breach flow of the roller compacted concrete gravity dam and so on. The'life and death'unit is used to simulate the concrete casting process. Before placement of concrete, the unit is considered'death', there is no temperature and stress; When the concrete after pouring, the unit is activated, the temperature field and stress field begin to develop, so the image can be simulated and the simulation of concrete pouring process, the calculated results can more genuinely reflect mass concrete behavior.In this article, an alpine region of a roller compacted concrete gravity dam, equivalent surface coefficient of heat transfer method and compared is used to calculate the non-covered heated board and heated board covered with different thickness of the dam under the condition of the temperature field and temperature and stress field, and devoted to the analysis of the cold calculation of the impact of stress on the concrete surface. Results the surface of the dam upstream face laying 6cm thickness XPS heated board, long-term permanent heat preservation, weaken heat transmission between concrete and environment, raising the temperature of the concrete surface, so that the original surface concrete temperature gradient occurs in the steepest parts of heat preservation material inside, leaving the surface of concrete temperature change slowed down, the gradient flattens, thereby reducing the winter or cold temperature stress when the concrete surface, effective to prevent the generation of surface cracks. At the same time, also analyzed the surface of heated board thickness, type, holding time, annual percentage change in the external environment on the concrete surface temperature heat preservation effect, which is useful for selection of suitable heated board.