Interim guidance issued for temporary fixings of metal decking

The British Constructional Steelwork Association (BCSA) has recently issued interim guidance for the design of temporary fixings of metal decking for practical construction in the UK. A copy of the interim guide can be downloaded from www.steelconstruction.info.

The interim guidance is the result of a comprehensive study carried out at the Building Research Establishment (BRE) between 2019-21 to investigate the behaviour of different fixing configurations for metal decking.

The investigation included a series of full-scale decking tests with different fixing configurations subject to wind uplift and a series of wind tunnel tests to determine the wind load on single storey buildings and high-rise buildings up to 15 storeys. The aim of this project was:

(i) to determine the possible loads taken by the individual fixings connecting the decking to the steelwork during the temporary fixed construction stage, and

(ii) to propose a simplified methodology for the design of such fixings.

The methodology given in the interim guidance is based on BS EN 1991-1-4 Actions on Structures. General Actions – Wind Loads and the UK National Annex and the measured pressure coefficients instead of the codified pressure coefficients.

By using the measured pressure coefficients, the wind uplift pressures are reduced and consequently this leads to a reduction in the forces taken by the temporary fixings. This design model shows that current standard fixing arrangements are generally suitable for buildings in the Midlands and South-Central regions of the UK and that most projects outside of these areas require heavy-duty/permanent fasteners to discrete zones of the floorplate.