Details

Autor(en) / Beteiligte

• Anastasopoulos, Dimitrios
• De Roeck, Guido
• Reynders, Edwin P.B.

Titel

One-year operational modal analysis of a steel bridge from high-resolution macrostrain monitoring: Influence of temperature vs. retrofitting

Ist Teil von

• Mechanical systems and signal processing, 2021-12, Vol.161, p.107951, Article 107951

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2021

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals Complete

Beschreibungen/Notizen

• •The operational dynamic strains of a steel bridge are monitored with FBGs for one year.•The modal characteristics of the bridge are systematically identified from the dynamic strains.•The mode selection process in automated with the use of hierarchical clustering.•The influence of temperature on modal strains and natural frequencies is investigated.•The influence of retrofitting on modal strains and natural frequencies is investigated. Vibration monitoring from strain data is a promising alternative to the more conventional acceleration-based monitoring because a dense measurement grid can be achieved at a relatively low cost and because strain mode shapes are more sensitive to local stiffness changes than displacement mode shapes. However, the feasibility of monitoring strain mode shapes of full-scale civil structures, where the operational dynamic strain levels are of very low amplitude and temperature changes can influence the modal characteristics, has remained an open question. The present work provides a proof of concept in which the deck of a steel tied arch railway bridge is instrumented with eighty Fiber-optic Bragg Grating strain sensors, multiplexed in four fibers, that are interrogated with a technique that achieves high accuracy and precision. For more than a year, the natural frequencies and strain mode shapes of ten modes have been automatically identified from operational strain time histories, with typical root-mean-square values of 0.01 microstrain, on an hourly basis. Furthermore, using these modal data, the influence of temperature fluctuations and that of a retrofitting of the hangers connecting the bridge deck and the arches, which took place during the monitoring period, are extensively investigated. Both have an influence on the overall stiffness of the bridge and therefore they result in clear changes in the natural frequencies. They do not have an influence on the local stiffness and therefore they do not influence the strain mode shapes, except when the retrofitting induces an interaction between previously well-separated modes.