FBG based strain monitoring in the rehabilitation of a centenary metallic bridge

Structural rehabilitation plays an increasingly important role in civil engineering, due to the large number of existing infra-structures needing urgent interventions to maintain an adequate level of comfort and safety. However, designing these rehabilitation processes is a highly complex task, since it involves the analysis of the initial structural condition and the safety verification. The building processes are also highly complex, requiring constant assessment during their execution to keep it effective and to not disturb the original structural system. In this context, many doubts frequently emerge regarding the different matters concerning a structural rehabilitation. Permanent or short-term structural monitoring has shown to have a unique potential in the search for answers to these doubts, enabling the assessment of both the initial structural condition and the effectiveness of the rehabilitation. This paper presents an approach for monitoring strains in steel bridges, using fiber Bragg grating sensors, in order to assess the structural behavior during the most relevant stages of a structural rehabilitation. The comprehensive monitoring program carried out on Eiffel Bridge, a double-decked centenary metallic bridge located in Northern Portugal, which was recently rehabilitated, illustrates the application of this approach. The goals and the usefulness of the structural monitoring applied to this bridge are described in detail. Most relevant results are used to illustrate the contributions that FBG based strain monitoring exerted on the rehabilitation process of this remarkable example of 19th century engineering.