Temporary Works Toolkit. Part 6: Backpropping of flat slabs – design issues and worked examples

In the first of two articles examining temporary works failures, Director of Structural-Safety, Alastair Soane, describes common reasons for their occurrence, illustrating the risks with a number of examples.

Current highway bridge designs in the UK tend to favour either composite steel girders with a precast or in situ concrete deck for long spans, or precast concrete beams with an in situ concrete deck for spans of less than 40m. This article considers temporary works, in particular the use of temporary supports, to precast concrete bridge beams during deck construction.

A structure in its permanent state cannot be ‘wished into place’. Appropriate consideration must be given to construction methodology so that permanent works can be optimised, temporary works minimised and trade interfaces simplified. This article presents a list of general, high-level considerations that relate to construction methodology and optimisation of temporary/permanent works, with a number of examples provided.