New concept for sensor-based bridge inspections - application of embedded, distributed fibre-optic sensors

The purpose of structural health monitoring (SHM) is to assess the condition of a structure in its terms of load-bearing capacity, serviceability and durability. Over the lifetime, both the influenc-ing variables and the structural properties change, and their resistance is subject to age-related modifications, i.e. the degree of utilization becomes time dependent. A particular feature of infra-structure constructions is their long service life. Cracks or strain distributions in concrete struc-tures are often good indicators of structural health. Cracks above a certain size and changes in the crack pattern are therefore recorded and documented including their crack width wk today as part of the bridge inspection process. They serve as the basis for a project-specific assessment of the structural safety, serviceability and durability of the components. According to current regula-tions, cracks are recorded every 12 years for the inner shells of Austrian road tunnels [1] and every 6 years for bridges in both Austria and Germany [2][3], whereby according to [2] a sensor based monitoring of the crack width changes is only carried out as part of a special intervention [4]. The reasons for this are that these investigations are time-consuming, and the longevity of conven-tional sensors is limited.