Monitoring the structural effects of internal swelling reactions in Aguieira bridges

The São João das Areias and Criz II bridges, located in the reservoir of Aguieira Dam, in the centre of Portugal, were affected by internal swelling reactions of concrete, which particularly affected their piers and foundations. Laboratory tests diagnosed both Alkali-Aggregate Reaction and Delayed Ettringite Formation as the causes of those expansions. This situation motivated important rehabilitation works on the piers and foundations of both bridges. These rehabilitation works was based on the construction of six piles around the footing of every pier founded on the riverbed. The corresponding pile cap was connected to the emersed part of the pier. In the course of these works, a structural health monitoring system was installed in each of these bridges in order to characterize the structural effects of the swelling reactions, both in the loss of rigidity and the temporal evolution of this degradation. The aim of this paper is to describe the instrumentation performed in these bridges and present the preliminary results achieved.