Modelling a Damaged Multi-span RC Bridge Based on Structural Monitoring Data

The paper reviews the monitoring, data analysis and modelling of a multi-span RC-bridge. The bridge is 102 m long, with six spans, crossing a glacial river in SE Iceland. The bridge was taken out of operation in 2019 when one of the bridge pillars subsided due to scour erosion. The Icelandic Road and Coastal Administration decided to use the bridge as a learning tool before it was demolished and a new bridge built on the same site. A realistic assessment of the structural properties and bearing capacity of existing bridges is a prerequisite for evaluating the safety of older bridges in the road system, which were designed according to outdated standards and different load conditions but are required to serve today’s traffic and future demands with an increasing number of heavy vehicles. The data presented in this paper are time series of acceleration measured for ambient loading on the bridge. A system identification analysis of the bridge was performed using two OMA tools. It is found that based on low amplitude ambient vibration data, the first four modes can be reliably estimated in terms of natural frequency and critical damping ratio, but the higher modes are more uncertain, and their identifiability varies depending on the data-set used. The results of the analysis are used to update and validate finite element models of the bridge that are used to interpret and simulate the observed vibrations.