Development and Analysis of a Vibrational Characteristics Database for Defining Application Boundaries of Infrasound for Bridge Structural Health Monitoring

Previous studies have documented the validity of infrasound as a supplementary tool for noncontact structural health monitoring of bridges. However, a more thorough understanding of when infrasound is applicable for structural health, with more monitoring, is necessary for this technology to be used as a tool in conjunction with traditional inspection and monitoring methods. Infrasound monitoring of infrastructure remotely detects the natural frequencies of the structures under observation. For bridges, these lowest frequencies generally relate to first-mode global oscillations of the main span, most often a flexural or torsional mode. For structural health monitoring, changes in the expected frequencies of the structure can be indicative of a problem. Therefore, a database of vibrational bridge characteristics for undamaged bridges is needed. This paper includes a synthesis of experimentally determined vibrational characteristics focused on correlating main span length and frequency for 116 bridges. The developed statistical models were then applied to a series of bridges for validation of the correlations that were developed. The results of this research provide insights into the applicability of infrasound as a structural health monitoring technique for vehicular bridges based on bridge type and define limitations based on expected frequencies related to processing, array layout, and deployment.