Reinforced Concrete Members Under Fire Temperature Field Numerical Simulation Study

Laws of temperature field distribution in concrete member under fire are the basis of the fire-resistant research of the reinforced concrete structures. Based on Hunan province science and technology key item, the entire process analysis and a simulation research about reinforced concrete frame structure under fire (06FJ2002), the computer software about the temperature field of concrete beam and column under fire is compiled. Finite element method combined with finite difference method is applied to the computer software simulation on the base of heat transfer theory. The computer software is used to simulate temperature field distribution laws of concrete structural member under three-face heated. The primary tasks are as follows:(1)The laws of thermodynamical parameters about concrete along with temperature at home and abroad are summarized and compared. The finite equations of section temperature field under fire are derived on the basis of the heat conduction fundamental equations in detail. The theoretical foundations of the temperature field software are laid firmly.(2) The heat transfer coefficient, which have great influence on the accuracy of the finite element equations in high temperature, are discussed and researched deeply. Lots of the factors, such as the reason of fluid creating, the fluid physical properties, the concrete member sectional dimension, the position and the shape of concrete member etc. are analyzed. The results will give an important reference to the future experiment research on the heat transfer coefficient.(3) The flow chart of temperature field analysis and calculation is established and the computer software is complied on the C++ platform. The reliability and validity of the software have been proven by comparison the test results with those from computer software simulation. The influence factors of temperature field such as thermal parameters, sectional dimension and the fire duration are analyzed using the software. The results indicated that the measured data about temperature field is basically identical with calculation data. The Identical thermal parameter values which get from diffent references have a little influence on the results. The temperature in every point of the identical section is different, and there exits great gradient of temperature in the section. The temperature is high when the measured points are close to concrete surface, otherwise the temperature is low. The above phenomenon illuminates that the increase of concrete protective coating thickness can enhance the fire-resistant capacity of concrete beam and column. The calefactive curves of different point in the concrete section almost have similar trends with the heating time going on.The results may apply to the concrete structure bearing capacity analysis under fire. Correlative conclusions will guide engineers to fire-resistant design and have some engineering practical values.