The investigation report into the Injaka Bridge collapse (NCE 8/15 August) is well worth a read by all those involved in major bridges - and it is easily accessible via NCE's website.
The source of the failure was the use of a slide path away from the webs of the bridge, caused in this case by a catalogue of errors, inexperience and confusion.
Hopefully this could not happen to UK engineers. However, a similar problem could arise from the current fashion for unusual forms.
We recently completed an alternative design using an incrementally launched method for a bridge across the estuary in Dublin.
The bridge has a curved soffit rather than the normal flat profile. The curvature meant that slide bearings had to be inclined and that normal tolerance errors could shift the slide path significantly from its intended line towards the thin curved slab. For this bridge the amount of movement could be calculated and allowed for in the design.
One half of the bridge has now been launched and the second deck is well on its way.
David Collings, technical director, Benaim (UK), David.Collings@benaimgroup . com