A study on the concurrent influence of liquid content and damage on the dynamic properties of a tank for the development of a modal-based SHM system

Remote detection of structural aging, degradation phenomena and damage due to hazardous events is critical to ensure safety and reliability of civil or industrial structures. This is the motivation of the rapid development and increasing application of fully automated structural health monitoring (SHM) systems in civil engineering. Modal-based damage detection currently represents a popular approach for SHM of civil structures. In fact, it is a global method for damage detection and, as such, the measurement locations are not required to be close to the damage. However, damage sensitive features defined in terms of modal parameter estimates are also influenced by environmental and operational factors. Thus, neglecting this influence might jeopardize the reliability of the technology. In this framework, the present paper investigates the potential of modal-based SHM to detect earthquake damage at anchors of an atmospheric liquid storage tank. To this aim, the influences of bolt loosening at supports and of liquid level on modal parameters are investigated. The ultimate goal of the present study is the definition of criteria for the effective design and application of modal-based SHM to liquid storage tanks.