Nonlinear computation method for simply supported beam of reinforcement concrete exposed to fire

It is our aim to analyze the mechanical performance on variation protective thickness and fire time of multiple load cases for reinforcement concrete simply supported beam exposed to three sides and full span fire. Tangential angle is adopted, and load factor method proposed for calculating the ultimate bearing moment for reinforced concrete simply supported beam. The variation law is analyzed under multi-load case, and the ultimate moment on mid-span section for simply supported beam of reinforcement concrete. The results indicate that load factor can reflect the variation law of ultimate bearing moment under condition of equal load value. Ultimate bearing moment approximately decrease as the relation of two broken lines, but increase linearly with the increase of concrete protective layer thickness. The control of fire time and increment of concrete protective thickness is effective in prevening the degree of fire damage. Therefore, the computation method is feasible.