Developing a robust simplified method for structural integrity monitoring of offshore jacket-type platform using recorded dynamic responses

Designing of the updated models for the damage diagnosis purposes is an important topic in mechanical and structural engineering due to its application in structural health monitoring. In the modeling of complex dynamic systems, the approaches for reducing the discretization error may fail to enhance the confidence in simulation based predictions when the dynamical systems exhibit significant changeability in the description of the numerical model due to model uncertainty. This work is an experimental research on a laboratory model of a jacket structure with the target of establishing a baseline finite element (FE) model for long-term structural health monitoring for this type of structures. Experimental vibration tests are performed on a hydro elastic physical platform model to obtain dynamic characteristics. Moreover, this research represents an algorithm based on the cross model cross mode (CMCM) method in combination with an iterative procedure along with introducing a simplified method that is named Pseudo simplified (PS) model technique. This technique is capable of damage diagnosis with limited, spatially incomplete modal data. Such techniques are paid more attention for marine structures due to their application in facilitating the difficulties through the health monitoring procedures. The proposed new technique (PS) provides a fast damage zone identification process. For this propose, we evaluated the selection procedure of the inactive degrees of freedom in process of the model reduction with a reasonable criterion by using the sensitivity analysis of system response under base excitation. Meanwhile, the FE model updating based on the empirical model utilized to overcome the uncertainty in modeling. The major problem inherent to dynamic analysis is that it is time-consuming, expensive and a high computational burden is involved. Therefore, development of such methodologies would be extremely useful to spread out technologies that can be applied for offshore platform in service with saving of both time and cost. (C) 2016 Elsevier Ltd. All rights reserved.