A method of analysis has been developed to simulate the behaviour of composite floors exposed to fire. The governing differential equation, based on the orthotropic plate theory, is solved by the finite difference method.The solution requires the calculation of plate rigidities as influenced by the thermo-mechanical properties of the materials. This is achieved by first calculating the temperature distribution in the floor. Numerical integration of stresses calculated from non-thermal strains, compatible with the appropriate temperature dependent stress-strain relations, enables ...