The neutral axis location for structural health monitoring: an overview

AbstractStructural health monitoring (SHM) is the process of continuously or periodically measuring structural parameters over time and the transformation of the acquired data into information about the actual structural behavior. The main goal of SHM is to provide quantitative and actionable information to infrastructure managers on a system-wide level. However, to achieve this goal, damage sensitive universal parameters need to be researched, identified, and implemented into SHM processes and data analysis. The neutral axis location has been identified as a potential parameter for damage detection, performance evaluation, and condition assessment of beam-like structures. This paper is intended to serve as a reference for researchers who are interested in the state of the art in evaluation of the neutral axis location, facts about the neutral axis behavior, and challenges associated with using the neutral axis for SHM purposes. Studies of the neutral axis in laboratory settings, controlled on-site testing, and on real structures in on-site conditions are presented and discussed. The main difficulties in using the neutral axis location for SHM purposes that are identified in this paper are: (1) its sensitivity to environmental effects such as temperature, humidity, and loading positions, (2) its natural variation in healthy cross-sections, (3) quantification of its sensitivity to damage, i.e. its damage detection capabilities in terms of the damage size and its distance from sensors, and (4) correlation between the neutral axis location and the capacity, performance, and condition of the monitored structure. The proof of concept has been provided with numerical modeling, and in the laboratory, and to some extent through controlled testing; however, a general on-site validation still remains a major challenge.

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