Verulam (readers' letters)

Institution Fellow, Bob Wilson, suspects that previous titles by Francis Ching notwithstanding, this latest offering might be of more interest to architects than structural engineers.

During remediation of distressed buildings in Dublin, horizontal cracks more than 20mm wide have been seen in the concrete block sub-structure walls. When pyrite-rich calcareous aggregate oxidises beneath a ground floor slab, it can raise and crack the concrete floor. In addition, it has been found that when tightly compacted fill expands, it may grip the substructure walls such that the whole super-structure is lifted off these support walls.

In this article, the various types of formwork and falsework needed to construct a concrete bridge are examined. The choice of bridge type depends not only on the general parameters of the scheme (such as typical spans, overall deck area, clearance requirements, alignment and the overall aesthetic), but also on the particular and local parameters of the site, many of which are related to construction.