Vibration Data as a Tool for Continuous Monitoring of Cable Tensile Loads

Abstract

The in-situ assessment of axial load in cables and prismatic members using flexural vibrations has been investigated for long time. The information about flexural modes in terms of natural frequencies and mode shapes is used to solve an inverse problem for the identification of the axial loads in the presence of a number of assumptions (known material properties) and eventual additional unknowns (i.e. type of constraints at the ends). The available methods for tensile load estimation represent a valuable solution for structural monitoring in operation, but a common drawback is the need for periodic modal identification tests and offline processing of the collected datasets. These techniques are therefore suitable for periodic checks rather than continuous monitoring. However, taking advantage of the most recent developments in the field of operational modal analysis, an automated system for continuous monitoring of axial loads based on dynamic measurements can be developed, as illustrated in this paper through a pilot application. After a review of the methods for axial load identification from vibration properties, the developed monitoring system for continuous monitoring of tensile loads is described.