A new design method to determine the membrane capacity of laterally restrained composite floor slabs

The companion paper to this one presented the method to determine the membrane capacity of composite floor slabs in fire. In this paper the method is applied to four of the Cardington fire tests. Two calculations were carried out for each test. Firstly, the design method was used to calculate the required deflection to carry the actual load on the floor. This would allow an assessment to be made of how accurately the method can predict the structual behaviour of a composite floor slab in fire. Secondly, the ultimate load capacity of the floor was calculated based on the chosen failure criterion of a limiting mechanical strain. This would show how close each test was to failure. Failure envelopes were also produced for each test showing the load capacity of the slab for a range of reinforcement temperatures. The results showed that the method can accurately predict the behaviour of composite floor slabs in fire with the predicted deflections agreeing well with the experimental results within the bounds of the assumptions made. It was also shown that the load capacity of the floors in all tests was significantly higher than the loads applied during the tests with the highest utilisation being 64% for the BRE large compartment test.

N. J. K. Cameron, BEng, PhD
Whitby Bird, 60 Newman Street, London, W1T 3DZ

A. S. Usmani, BE, MS, PhD, CEng, MIStructE
School of Engineering and Electronics, University of Edinburgh, Edinburgh, EH9 3JN