Early temporary works planning is vital.
While many may regard temporary works as the poor relation of structural design, it can provide fascinating technical challenges and is often vital both to the commercial success of a project and to health and safety.
Although the design of a working platform may seem mundane, the recent Saudi crane tragedy with over 500 casualties including 111 deaths may well prove to show what can happen when temporary works fail.
Fortunately in the UK over recent years, many contractors, as part of improving health and safety, have been formalising their temporary works approach and ensuring items are rigorously designed and documented.
Despite that, thinking about temporary works is often left late in the design and the procurement process. Too often we see the temporary works installed for demolition clashing with the temporary works for construction which in turn is found to clash with the permanent works. The subsequent rejigging of the temporary works is costly and could be avoided by setting out a suitable strategy at the start of the project.
While the temporary works will be dependent on the contractor’s method of working, it is important that they are considered during the design process to ensure that the design is practical and to identify potential clashes and risks. In some instances, the temporary works solution can be a driver for the design and construction process.
So, for instance, the decision to construct a basement top down or traditionally will be highly dependent on the required propping solution. Similarly, façade solutions are often chosen so that they can be installed from within the building avoiding the need for an external scaffold.
Temporary works designers need to design for a range of load cases, from plant and construction activities to varying loads from the permanent works during construction.
For items like façade and basement wall support, deflections rather than loads may be the governing criteria.
Frequently, designing for demolition will need to be considered, looking both at transferring loads from temporary to permanent works and ensuring that there is adequate access for the safe dismantling and removal of the components.
It is also is important that the permanent works designers understand the issues and make adequate allowances in their design to ensure that they can be built safely and economically.
This may be as simple as allowing adequate clearances for piling rigs or scaffolds and hoists. Designing the ground floor slab for construction traffic may require minimal strengthening but can remove the need for propping, freeing up basement space for following trades.
For all projects, early consideration of temporary works requirements and strategy can reduce costs and programme while improving health and safety. The whole project team should therefore have a good understanding of the relevant issues and it is important that engineers’ training covers this.
- Richard Thiemann is a director of Byrne Looby UK