"Because of a phenomenon called 'tensile membrane action', the majority of composite floors in multi-storey construction could be designed to have fire protection only on the columns and primary beams, with secondary beams left unprotected," says BCSA manager of fire and sustainability John Dowling. This is because a composite steel floor plays a crucial role in providing enhanced fire resistance, something which is not apparent in test results for single, isolated members. Leaving beams unprotected enables the slab to develop tensile membrane action.
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