Dr Samia J Alkizwini: Composite floors exposed to fire
Composite floors exposed to fire
byDr Samia J Alkizwini
Abstract
A method of analysis has been developed to simulate the behaviour of composite floors exposed to fire. The method comprises both thermal and strength analyses. The governing differential equation, based on the orthotropic plate theory is solved by the finite difference method. The solution requires the calculation of the plate rigidities, as influenced by the thermo-mechanical properties of the constituent materials. This is achieved by first numerically integrating temperature dependent stresses to obtain the moment stress-resultants and dividing these by the local curvatures.
For each stage of fire, a small number of iterations are required to achieve equilibrium. Starting from the ambient temperature, the response of the structure is calculated as the fire develops. Computations are halted when equilibrium can no longer be obtained. This defines the fire duration of the composite floor.
The method has been validated through comparison with a number of published fire tests. The comparison shows excellent correlation. The formulation covers a number of idealised support conditions. A parametric study has also been carried out on floors with different boundary conditions subjected to in-plane forces. Comparison of mid-span deflections has shown that floors with fixed edges have better fire resistance than simply supported floors.