Assessment of the damages occurring between two adjacent measurements for an aging offshore platform

Abstract A new damage assessment method is proposed for aging offshore platforms based on dynamic tests, which can provide information on whether damages occurred between the times of two adjacent measurements. A new damage indicator is defined to reduce the influences of existing damages accumulated before the first measurement. One theoretical improvement is that the requirement for using the stiffness of the finite element model to replace that of the measured model is unnecessary in the calculation of the modal strain energy. The other is that damages that occurred in periodic measurements of aging platforms can be assessed separately, even for those platforms that have not been tested during their previous service life. A numerical jacket platform is chosen, and the results show that the proposed method can properly identify the damages that occurred between the two measurements and can estimate the damage severity, even when 5% corrupted mode shapes are used. In addition, the method also can greatly reduce the influence of the damages accumulated before the first measurement, which means that the platform׳s integrity can be assessed by implementing periodic dynamic tests without any other test data.

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