Loading bays and towers are commonplace scaffold structures, with a variety of types, construction methods and safety aspects to consider for this valuable and time-saving scaffold assembly. Ian Hale, a structural engineering consultant from S-Mech Ltd, discusses the details.
The design of loading structures is an important consideration in the specification of a working scaffold. The design loadings can be five times greater than the main scaffold and sometimes more, therefore this critical element should be given due time in the detailing process to ensure a safe structure is provided.
Loading towers can be provided in tube and fitting, system scaffold and, perhaps most advantageously, in a hybrid arrangement with a system loading bay against a tube and fitting scaffold. This is beneficial because it provides not only totally flexible positioning along the length of the scaffold but also a completely separate gravity load path for the loading bay forces to travel safely to the ground. System-type loading bays are also generally quicker to erect than their more traditional counterparts.
A variety of methods are available to form the loading deck, with ladder beams and board-bearing transoms the usual arrangement for a five-board tube and fitting bay. With system scaffold, it is more common to adopt board bearers spanning between system loading bay beams, which allows a larger 2.5m deep bay to be constructed. All loading bays rely on the plan and facade bracing for their structural stability, and it is critical that this bracing is not removed or altered while the loading bay is erected. Design guidance for system scaffold must be taken from the manufacturer’s user guides, while details for tube and fitting loading bays can be found in common industry guidance documents. Alternatively, a scaffold designer will be able to detail specific solutions for any unusual requirements that a site may demand.
Loading bays are traditionally designed for a ‘blanket’ loading of 1 tonne per square metre (10 kN/m2), plus an allowance of 25 per cent for light mechanical loading of materials. In some arrangements of system scaffold loading bays, the allowable loading can vary, hence the importance of always referring to the manufacturer’s guide when constructing a system loading bay.
The safety of operatives when using loading bays is critical due to the risk of falling if a free edge is present, and this has recently been the focus of a discussion with the HSE. The latest variants of ‘up and over’ safety gates are designed to reduce this risk significantly by placing the operatives behind a barrier at all times. Gates are now available in aluminium and steel to suit both system and traditional scaffolds, including extendable versions to solve the problem where irregular bay sizes are required.
A Loading Tower User Guide is available from VR Access Solutions.
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Ian Hale BSc (Hons) MSc CEng MIStructE