Masonry structure strengthening – Reinforced shotcrete counter-arches
In 2016, Freyssinet’s partner, Sixense, was contracted to inspect and examine the combined concrete and masonry structure of the Sahasinaka viaduct. During its investigations, Sixense detected signs of erosion around the foundations for the central pier (the viaduct’s highest pier at 39 metres high), causing subsidence. Freyssinet’s teams were urgently appointed to inject cement grout in a bid to consolidate the foundations, which helped stabilize the structure and prevent any further settlement. But the concrete arches on either side of the damaged pier also needed reinforcing, since the differential movement had fractured the concrete. A second contract was therefore awarded to strengthen the arches, and work began in May 2019. The main aim was to structurally reinforce the underside of the two arches by creating reinforced shotcrete counter-arches supported by concrete beams (corbels) fixed to the piers with Freyssibar prestressing bars.