Offshore installations must be built to resist fatigue as well as extreme forces caused by severe environmental conditions. The structural reliability analysis is the popular practise to assess a variety of natural waves determined by the long-term probability distribution of wave heights and corresponding periods on the site. In truth, however, these structures are subjected to arbitrary wave-induced forces in the open ocean. Hence, it is much more reasonable to account for the changed loading characteristics by determining the probabilistic characteristics of the random loads and outcomes responses. The key challenges are uncertainties and the non-linearity of Morison’s drag element, which results in non-Gaussian loading and response distributions. This study would analyze advances achieved to date in a comprehensive probabilistic review of offshore fixed jacket-type platforms.

The structural integrity of offshore platforms is affected by degradation issues such as subsidence. Subsidence involves large settlement areas, and it is one of the phenomena that may be experienced by offshore platforms throughout their lives. Compaction of the reservoir is caused by pressure reduction, which results in vertical movement of soils from the reservoir to the mud line. The impact of subsidence on platforms will lead to a gradually reduced wave crest to deck air gap (insufficient air gap) and cause wave-in-deck. The wave-in-deck load can cause significant damage to deck structures, and it may cause the collapse of the entire platform. This study aims to investigate the impact of wave-in-deck load on structure response for fixed offshore structure. The conventional run of pushover analysis only considers the 100-year design crest height for the ultimate collapse. The wave height at collapse is calculated using a limit state equation for the probabilistic model that may give a different result. It is crucial to ensure that the reserve strength ratio (RSR) is not overly estimated, hence giving a false impression of the value. This study is performed to quantify the wave-in-deck load effects based on the revised RSR. As part of the analysis, the Ultimate Strength for Offshore Structures (USFOS) software and wave-in-deck calculation recommended by the International Organization for Standardization (ISO) as practised in the industry is adopted to complete the study. As expected, the new revised RSR with the inclusion of wave-in-deck load is lower and, hence, increases the probability of failure (POF) of the platform. The accuracy and effectiveness of this method will assist the industry, especially operators, for decision making and, more specifically, in outlining the action items as part of their business risk management.

Offshore structures are exposed to random wave loading in the ocean environment and hence the probability distribution of the extreme values of their response to wave loading is required for their safe and economical design. Wave loading on slender members of bottom-supported jacket structures is frequently calculated by Morison's equation. Due to nonlinearity of the drag component of Morison wave loading and also due to intermittency of wave loading on members in the splash zone, the response is often non-Gaussian; therefore, simple techniques for derivation of their extreme response probability distributions are not available. To this end, the conventional time simulation technique (CTS) is frequently used for predicting the probability distribution of the extreme values of response. However, this technique suffers from excessive sampling variability and hence a large number of simulated response extreme values (hundreds of simulated response records) are required to reduce the sampling variability to acceptable levels. In this paper, a more efficient version of the time simulation technique (ETS) is introduced to derive the probability distribution of response extreme values from a much smaller sample of simulated extreme values. The ETS procedure is found to be many times more efficient than the CTS method.

An offshore structure is operated in an ocean wave environment that is stochastic in nature. Essential knowledge of ocean wave mechanics is practically important when it comes to the reliability of the structure. This paper summarised the numerical formulation involved in representing the ocean wave which will provide interaction effect in the design load of offshore structural response. Mechanism of wave load involved the formulation of wave spectra, ocean wave theory, water particles kinematics above sea water level, and the evaluation of wave force. Several formulations introduced by previous researchers for each process of wave load mechanism are discussed. At the end of this study, a good understanding of the estimated wave loads-induced responses will be discovered in terms of the selected ocean wave modelling. In application perspective, the calculated offshore structural responses would be utilised as the design load (structural responses) in structural reliability analysis of offshore platforms.

The reliability of offshore structure is dominantly affected by the wind-generated random waves load. Hence, an appropriate technique is required in predicting the extreme response due to the dominant load. Monte Carlo (MC) time simulation is said to be the most accurate technique. However, such analysis leads to a large number of response records which is computationally demanding. Current finding shows that a modified finite-memory nonlinear system offered more efficient technique. Still, the accuracy is getting severe once negative current is considered. Hence, improved version of MFMNS technique is required by modelling the residue between the extreme values from MC and the approximate MFMNS techniques; known as the eMFMNS technique. In advanced, a comprehensive study on eMFMNS technique will be carried out involving a wide range of environmental conditions. From the investigation, it is proven that eMFMNS technique improved the accuracy in predicting extreme values compare to MFMNS technique.

The search for potential investors in the conversion of ocean thermal energy to power or hydrogen, and its spinoff projects in Malaysia and the region, continues. In the meantime, several pre-feasibility studies have been completed for selected sites, including that of Pulau Layang-Layang and Pulau Kalumpang (Sabah, Malaysia); Timor-Leste, and off Pulau Weh (Aceh, Indonesia). Various research projects have been completed such as the conversion of solar-thermal to the chilled-water system; the cooling of tropical soils for the culture of temperate crops; the design of offshore structure off the continental slope; hydrogen fuel production and distribution, deep seawater properties to reduce obesity, cholesterol and blood pressure; and the legal-institutional framework for the development of ocean thermal energy conversion. UTM Ocean Thermal Energy Centre (UTM OTEC) has entered into the Collaborative Research Agreement with the Institute of Ocean Energy of Saga University (Japan) to undertake joint research for the development of an experimental rig that introduces a hybrid system with stainless steel heat exchanger. Other aspects of this joint research would include a new design for 3 kW turbine, the introduction of nano-working fluids, the eDNA of intake waters, and improved productivity in the culture of high-value marine produce and products.