Improved damage detection algorithms for offshore jacket platforms based on partial measurement

Newly derived algorithms of two indices to predict location and severity of damage in a structure using partial measurement of vibration in a target detecting region are proposed. The feasibility of the damage-detection algorithms are tested by employing a numerical model of an offshore jacket platform for which pre- and post-damage modal parameters are available for a few lower modes of vibration. Regarding the simulated dynamic responses of the platform under white-noise ground excitation as ambient vibration measurement, modal parameters are identified by employing an ARMA method, and the two indices are applied to locate damages and estimate severity of them simulated in the structure. It is demonstrated that the two algorithms are feasible for damage location and the second one (Damage Index B) is practical for severity estimation.