Deck replacement and seismic piers retrofitting without any traffic stop: the Fornello viaduct

The \u201cFornello\u201d viaduct, on the Orte to Ravenna Express-Way in the Northern Italy, consists of twin parallel P.C. decks, one for each direction, having a middle span of 114.65 m and two side spans of 51.625 and 53.125 m. They were built at the end of \u201860s using the cantilever launching technique starting from box piers, about 33m and 18m high. The high deformability of the deck determined discontinuities in the vertical alignments at mid-span due to long-term loads and vibration phenomena caused by short term loads; this created serious problems to the traffic. For this reason, the Highway Authority had to carry out repeated investigation and tests on the concrete deck; the mechanical strength resulting from these tests were significantly lower than the design values. The deck could not be maintained and, therefore, a replacement was necessary. The deterioration of piers was of moderate entity, but a static strengthening was needed as a consequence of the increase in seismic reference requirements due to a new seismic risk zoning in the site. This paper reports on the solutions adopted, focussing on the ways in which the new requirements of strength and serviceability were addressed, particularly with respect to durability and the relationships between the new structures and the setting, which is a landscape of special value