Structural Retrofit and Health Monitoring of Colle Isarco Viaduct

With its 13 spans and total length of 1028 m, Colle Isarco Viaduct is among the longest bridges in the Alpine region and is a link of strategic importance on the highway corridor connecting Northern Italy to Austria. Its longest span, 163 m long, is spanned with balanced cantilevers of depth varying from 2.85 m to 10.80 m, supporting a suspended span. The bridge was designed and built between 1968 and 1971 and underwent repair interventions in 1988, 1999 and 2007. To cope with today’s growing traffic load demand, the bridge was recently further retrofitted through installation of an external post-tensioning system. The effectiveness of this work, completed in 2015, is currently being assessed through extensive structural health monitoring. The monitoring instrumentation includes a topographic network, operating since summer 2014; load cells recording the tension of the new post-tensioning cables; and a network of fiber optic strain gauges and PT100 temperature sensors, to be installed by the end of 2016, and expected to provide detailed information on the strain and temperature fields of the cantilevers. In this note, we illustrate the bridge, its history and the past maintenance works. We describe in detail the rationale behind the design of the new monitoring system and how the data acquired shed light on the observed past behavior of the bridge and on the effectiveness of the new retrofit intervention