4.5 - Bearings / Support

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In accordance with BS5950 and Eurocode 4, the ends of all deck sheets (and edge trim) require a minimum end bearing onto a structural support. Adequate support should be designed/detailed by the steel frame designer (this may be the structural engineer or steelwork contractor depending on the contract specifics) and manufactured/installed by the steelwork contractor.


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When a 2D/3D CAD model is received, where possible, SMD will endeavour to highlight missing supports or additional requirements during the design/detailing process. However, the design, supply and installation of these supports is the responsibility of others.


The following guidance has been prepared to aid steelwork designers during the detailing process to ensure the minimum support requirements are provided at junctions between beams, columns and walls. Whilst this guidance is not exhaustive it provides the general principles that can then be applied where obstructions such as bracing, baseplates, splice plates etc obstruct the surface of the supporting structure.


4.5.1 End bearing

The minimum bearing requirements for deck and edge trim is 50mm* on steelwork increased to 60mm where deck sheets are to receive thru-deck welded shear studs, (refer to Section 6.0 - Design - Floor deck composite beam design) and 70mm on masonry or concrete. The 114mm dimension is the minimum recommended edge distance between the shear stud and slab edge for composite edge beams designed in accordance with BS5950 or BS EN 1994-1-1.


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Where the deck is to butt up against a concrete core or similar, shelf angles are to be installed by others to provide adequate end bearing for the metal deck (Fig 4.5c). When developing such a detail, consideration must be given to the height of any continuity reinforcement extending from the core to ensure it does not clash with the troughs of the deck profile.


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Where the deck runs parallel to a core wall (Fig.4.5d), an angle may not be necessary (It may be possible depending on spacing of secondary beams to utilise a 2.0mm gauge flashing to avoid the requirement for a structural angle, however this will impact on the slab capacity for high concentrated loads locally in the region of the non-structural flashing).


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4.5.2 Shelf Angles or bottom flanges

To reduce the structural zone it is sometimes necessary to install the decking onto angles fixed to the beam webs or bottom flanges. Where deck ends are supported on shelf angles or bottom flanges between beam webs, the shelf angle or bottom flanges must be designed to extend a minimum of 50mm beyond the toe of the beam top flange. This minimum dimension of 50mm is essential to enable the sheets to be physically positioned between toes of top flanges and provide access for a cartridge tool to be used to secure the decking into place (Fig 4.5e).


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Where the deck spans parallel to the beam web a structural support angle is the recommended detail (Fig 4.5f). It may be possible depending on spacing of secondary beams to utilise a 2.0mm gauge flashing to avoid the requirement for a structural angle, however this will impact on the slab capacity for high concentrated loads locally in the region of the non-structural flashing.


Refer to SMD Data sheet SMD.DOD.177 - Decking Bearing of Shelf Angle


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4.5.3 Deck bearing at obstructed top flanges

Where a connection plate, post, bracing or similar obstructs the beam top flange, additional plates must be welded either side to extend the top flange and ensure a minimum of 50mm bearing for the deck end is provided.


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4.5.4 Deck support at face of columns

Column flanges that have no incoming beam require additional support to deck ends where columns exceed 150mm wide for R51+ and 100mm wide for TR60+ and TR80+. This applies for any unsupported sections of deck end with the dimension taken perpendicular to deck span.


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Columns between 100mm and 150mm, there can be instances where the deck is completely unsupported at the end bearing (should the deck fall central to the column). In the instance shown in Fig. 4.5j where TR60+ is detailed, it will result in two ribs of the deck sheet being unsupported.

When designing with roof deck, additional support will be required to columns in all cases.

Where deck is running in the opposite direction to that shown in Fig. 4.5h, no additional support is required.


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