Accurately assessing the reliability of ageing structures is essential, especially in the oil and gas industry where inaccurate predictions of structural performance may have significant hazardous consequences. This study aims to develop a time-dependent pit depth corrosion model for subsea gas pipelines. This model is formulated with the parameters as function of age using the 3-parameter Weibull distribution function. The developed model gives the prediction of the pit depth of a gas pipeline at any given age by changing the scale, shape and location parameters. Measurement data for gas pipeline corrosion pit depth were collected and the statistical characteristics were quantified by statistical analysis in terms of gas pipeline age. The results and outcomes of the present study will be useful for predicting the corrosion pit depth of gas pipeline structures and can be used in the design stage of a new gas pipeline structure.

This paper presents a computational fluid dynamics (CFD) study of vortex-induced vibration (VIV) for different aspect ratio (L/D) cylinder. Of particular interest was to measure hydrodynamic forces and numerically investigate the wake behaviour of VIV while varying the aspect ratio. The simulation models represented the actual experimental conditions with idealised free-surface boundary condition to capture the responses from fluid-structure interaction phenomenon. The simulations were performed in the subcritical flow region (7.4×10³ < Re < 2×10⁵), corresponding to a range of reduced velocity (U_r) from 2 to 14. The results of the cases studied were discussed and compared with the experimental data to verify the accuracy and validity of the present simulation. The comparisons have shown a similar curved-shape drag coefficient plot, and however underestimated the value of the drag coefficients over the reduced velocity. Additionally, the simulations seemed to capture a higher lift force response compared with the experimental data for a low aspect ratio. The correlation length was observed to be longer for larger aspect ratio and proportionally decreases as the aspect ratio decreases.

Overtopping breakwater for energy conversion (OBREC) is integration between breakwater and wave energy converter (WEC) that allows incoming waves to be stored in the reservoir. The higher the overtopping amount collected in a reservoir, the greater the energy generated will be. Hence, most of the overtopping concept has attempted to maximize the inclusion of water in the reservoir by optimizing geometrical parameters, particularly the ramp angle. However, the studies corresponding to ramp shapes geometries have not been adequately reviewed. Most studies only focused on the usage of linear overtopping ramp shape. There is still limited knowledge on the influence of different ramp shape parameters towards the overtopping wave. Thus, this paper aimed to push the border of available knowledge by investigating the influence of the ramp shape parameters to the overtopping wave discharge through simulation and experimenting approaches. Seven different ramp shapes have been tested under Malaysia’s wave condition and a new ramp shape parameter allowing for maximized overtopping wave on OBREC is presented.

Continuous assessment of aged offshore structures is becoming extremely important to avoid any hazardous consequences throughout their design life. In Malaysian waters where most of the offshore structures are jacket platforms, it was found that many of these structures are currently operating beyond their design life. With continuous corrosion taking place, structural reliability and operation will be affected. Therefore, for the safety evaluation, this study focuses on the reassessment of an existing aged jacket platform in Malaysian waters pertaining to corrosion effect. In this study, pushover analysis was carried out to determine the ultimate strength of the corroded jacket platform by quantifying the reserve strength ratio value. Two different time-dependent corrosion wastage models were used in the present study to simulate the corrosion behaviour at the splash zone of the jacket platform. It was observed that average corrosion condition relatively simulated the calm waters of Malaysia and by applying this corrosion, the jacket platform can withstand the environmental load acting on it. The results developed in the present study will be useful for future study in predicting and modelling corrosion tolerance of jacket platforms in Malaysian waters.