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In the study of structural strength, the reserve strength ratio provides a measure of the ultimate strength capacity of a structure. Under actual site conditions, the reserve strength ratio may vary from its design values with loss of stiffness and changes in structural integrity. Changes in the vibrational response of a structure due to loss of stiffness is observed as a form of structural health monitoring (SHM). The aim of this study is to investigate the relationship and sensitivity of the reserve strength ratio of a structure to changes in natural frequency due to damage occurrences as a measure of global structural integrity. The reduction of stiffness is simulated by the sequential removal of members according loading path within the model. To obtain the values used for comparison, a non-linear pushover analysis and eigenvalue analysis is utilized to obtain the Reserve Strength Ratio (RSR) and eigenvalue for intact as well as simulated progressive damage conditions. The pattern recognized from the analysis performed indicated that as the reserve strength ratio (RSR) is reduced with reduction of stiffness by the removal of primary and secondary members, the eigenvalues for each respective model showing similar reductions.

In Malaysia, over 400 oil and gas platforms are in operation. In every life cycle of a platform, it undergoes decommissioning. The most used method is by relocating the asset to an onshore fabrication facility. The alternative to onshore decommissioning is by reefing structures in-situ or ex-situ basis. to achieve the environmental assurance of a successful decommissioning by reefing, two domains of parameters were overviewed. the study involved hydrodynamic simulation of platforms. The first domain is in relations to the site to determine its suitability against hosting marine life and thriving coral formulation (Site Suitability). the other domain is in relations to the structure's physical and hydrodynamic properties (structural viability). Site suitability is governed by water depth and current velocity. Structural viability is governed by two sub-domains, one is where dimensions and complexity of the structure are assessed using dimensionality analysis. And the other is its hydrodynamic properties (Vortex Shedding Frequency, Pressure, Wake Region indices).