Behaviour of slabs in composite bridges

Abstract

Cracks have been observed in concrete deck slabs of composite bridges, in which composite action is achieved at the time of concrete curing. A study of the thermal behaviour of composite deck bridge slabs, during concrete hydratation, has been undertaken with the aim of explaining this cracking. Measures taken in a site, have shown that the thermal behaviour is the origin of transversal cracks about 0.1 - 0.2 mm wide, observed aproximately two weeks after concrete placement. This cracks are very well distributed (each about 2 m. apart) and do not widen significatively with time. The aim of current work is to determine the main parameters influencing termal cracking, and to reduce their effects. For this reason, special attention is paid to concrete technology and to placement procedures. From a general point of view, it is important to know that the cracks observed in composite bridges in the last 20 years, are not symptom of reduced structural safety, and do not seem to affect durability.