Experimental comparison of three automatic operational modal analysis algorithms on suspension and floating bridges

Abstract

Automatic operational modal analysis is necessary for long-term monitoring of structures when using modal information. Many algorithms have been proposed to accomplish this task; two examples are the fully automatic algorithm by Reynders et al. in 2012 and the semi-automatic algorithm by Kvåle and Øiseth in 2020; however, few in-depth direct comparisons exist. This work compares the two algorithms mentioned above with a new fully automatic algorithm recently developed by the authors, inspired by the best functioning elements from algorithms published since 2008 and following the standard three-step framework. The comparison is performed using 3600 experimental datasets from three real bridges – the Hardanger and Hålogaland suspension bridges and the Bergsøysund floating pontoon bridge – where the detections made by the algorithms are compared to the pre-defined reference modes of the bridges. The new algorithm (Dederichs 2023) performs equally to the Kvåle 2020 algorithm in correct detections and better than the Reynders 2012 algorithm. The two best algorithms detect the easily excited structural modes in over 90 % of the datasets. The Reynders 2012 algorithm is shown to have a more cautious approach to mode detections, making few correct detections and fewer errors. A sensitivity analysis of the criteria to compare detected modes to reference modes shows that this does not impact the comparison’s conclusions.