Swelling effects in a reinforced concrete pier of Foz Dão bridge (Portugal). First approach for modeling and behavior interpretation

Abstract

The degradation of the Foz do Dão bridge, that served the IP3 road and is located over the Aguieira dam reservoir, in Portugal, mainly due to the internal swelling reactions in concrete, resulting in visible cracking in its piers, led to the bridge re-placement in August 2015. Since 2009, this bridge has been subject to several in-spections, including underwater inspections, laboratory tests of cores, as well as periodic geometric levelling of the deck and ambient vibration tests. These actions were aimed to characterize its structural behaviour and to detect damage growth that might jeopardize safety. The aim of this work is to characterize and interpret the structural behaviour of the highest pier. For this purpose, a three-dimensional numerical model, which consid-ers the environmental conditions and the time-dependent behaviour of the concrete, was developed. The loads applied to the pier are the dead-weight of pier and the weight of the bridge deck, the pressure of the reservoir water, the effects of the thermal variations and of the swelling. The computing of the expansions considers the influence of the temperature and of the confining effect of the rebars and of the stress fields. The temperatures variations at the pier were computed using a thermal model. The model was calibrated considering data obtained by laboratory tests, on samples extracted from the bridge and by the deck levelling.