The new Fornello viaduct: method of seismically strengthening the piers and replacing the deck without interrupting traffic

The old Fornello viaduct, on the Orte to Ravenna state highway in northern Italy, consisted of two parallel precast concrete bridges, one running in each direction; both bridges have a central span of 114,98m and two lateral spans of 53,89m and 53,71m, and rest on two piers 30,18m and 18,69m 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 traffic problems. Static strengthening was also required to meet new seismic requirements. 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. Keywords: seismic actions, steel-concrete structures, slab cracking control, seismic retrofitting, creep, shrinkage.