Mesosopic Numerical Simulation And Engineering Application Of High Thermal Conductivity Concrete

The effective thermal conductivity of concrete used in civil engineering is low,and under the influence of environmental factors such as solar radiation and sudden change in temperature,it will produce large temperature effect inside the structure,which may lead to cracking of concrete structure.In order to reduce the temperature effect of concrete structure and to prevent the concrete bridge structure of the temperature cracks,the effective method is to improve the effective thermal conductivity of concrete.The main research subjects are the mesosopic numerical simulation and engineering application of high thermal conductivity concrete.(1)The mesoscopic numerical method of the effective thermal conductivity of concrete with arbitrary gradation and its modified method considering porosity are proposed firstly according to mesoscopic characteristics of concrete,and the validity of the two methods is also confirmed.The results show that both methods can predict the effective thermal conductivity of concrete,and the latter is more accurate.Simultaneously,the 2D gradation curve of coarse aggregate is proposed and proved to exist,and there is a one-to-one correspondence between 2D gradation curve of coarse aggregate and 3D gradation curve of coarse aggregate.(2)Based on mesoscopic numerical model of concrete with arbitrary gradation,the establishing method of the mesoscopic numerical model of steel fiber concrete with arbitrary gradation is proposed.The effect of steel fiber content,the replacement rate of iron ore sand for fine aggregate,aggregate type and aggregate volume fraction on the effective thermal conductivity of concrete,and the relevant suggestions to improve the thermal conductivity of concrete are given.(3)The heat transfer boundary conditions are constructed by using the principles of solar physics and meteorological data,and the calculation formula of unsteady temperature field under type?and type ? coupled boundary conditions is derived based on heat transfer and functional extremum algorithm.The method of calculating the nonlinear transient temperature field of the concrete bridge tower is also illustrated systematically,and the validity of this method is also confirmed according to the measured results of the temperature field of the two bridge towers.At the same time,the characteristics of sunshine temperature distribution of solid cross section and hollow section bridge towers are studied respectively.(4)Taking concrete bridge tower as an example,the influence of the effective thermal conductivity of concrete on the temperature effect of the bridge tower is studied by using the calculation method of nonlinear transient temperature field and relevant conclusions on numerical simulation of high thermal conductivity concrete,which provides the basis for the application of high thermal conductivity concrete in engineering.