Study on Heat Flow Analysis Model of H-Section Steel Columns with Box Protection under Fire Conditions

In this paper, a finite element analysis model is presented for the calculation of the temperature history of H-section steel columns protected with box-casing insulation under fire conditions. The FEA model is focused on simulating heat exchanges in the cavities between the steel column surfaces and fire proof boards. The thermal conductivity of the air and the heat transfer by convection in the cavity was neglected, and only the heat transfer by radiation between the interior surfaces was calculated. The effective radiative heat flow system of equations is derived and expressed in matrix form. The system of equations features a symmetric coefficient matrix and can be solved using LDL^T factorization. Node radiative thermal loads are calculated from effective radiative heat flows at segments, i.e., edges of elements located on internal cavities. Comparisons between predictions from the computer program TFIELD and test results show that the analysis model is capable of predicting acceptable results and is useful for performance based fire safety design of steel structures.