Improvement of structural monitoring of jacket platform

The offshore platform VEGA-A is eight legs fixed jacket structure operating from 1988 in the Sicily channel (Italy). In the platform is installed an environmental and structural monitoring system. In September 2015 the processing mode of the acquired data was modified, in order to better establish its representativeness in relation to the structural health monitoring (SHM) of the platform. This paper shows the results of the data processing provided by the monitoring system, employed to perform spectral analysis and dynamic identifications. The frequencies and the mode shape were analyzed in order to assess their variability during the life of the platform. The variation of mode shapes and main periods can be related to the damage of structural elements (columns and bracings) or to mass variations. The position of accelerometers can be optimized to detect, if any, different structural elements failures. The research includes the analysis of the accelerometer signals in order to improve the identification of damage correlated to significant events and for the selection of proper warning thresholds and alarms.