Kurian V. John

Hydraulic investigation of the H-type floating breakwater

Floating breakwaters are commonly used for wave protection of onshore and offshore facilities in the last decade. The majority of the floating breakwaters developed in the past are solid-type structures that have fixed drafts and may be highly reflective to the incoming waves. In this study, the H-type floating breakwater is proposed to serve as a wave attenuator instead of a wave reflector. The buoyancy of the breakwater is controlled by the placement of sandbags in the chamber embedded within the main body of the structure. The study aims to investigate the hydraulic properties of the H-type floating breakwater in random waves via a physical modeling. The hydraulic characteristics of the breakwater are quantified by the reflection and transmission coefficients as well as the energy dissipation coefficient. The experimental results have shown that the H-type floating breakwater is hydraulically efficient and provides high wave attenuation capability when subjected to short-period waves.

Finite Element Analysis of Guyed Offshore Monotower Subjected to Extreme Environment in Malaysian Water

This paper presents the finite element structural sensitivity analysis of a cable guyed monotower known as the Tarpon Monopod when subjected to extreme environments in Malaysian waters. A hydrodynamic loading and static platform response analysis is performed in SACS v5.3 to gauge the structural robustness in extreme Malaysian metocean conditions. A Stokes Fifth Order Wave Theory was employed to obtain wave kinematics and dynamics for load computation. The Tarpon Monopod design is reviewed generically. An actual platform located in 60m water depth within Malaysian waters is modelled for analysis. Four different guying cable scenarios are considered which are the fully guyed condition (three guy cables pinned), two guy cables condition (one wire loss), one guy cable condition (two wire loss) and free standing condition (total loss of guy wires) are presented. The environmental load sets are simulated at different headings using 45 degree steps. The results suggest that the structural caisson contributes little to the lateral stiffness of the platform. The Tarpon Monopod has little structural redundancy and its integrity is highly dependent on guy wire condition and environmental load headings.

Environmental load modeling for offshore Malaysia regions

Rapid expansion of oil and gas industry in 20th century increased the demand for accurate and reliable environmental load prediction. With the increase in natural disasters like tsunami, typhoon, and rise in water level from global warming, it is very important for engineers to model the environmental load accurately. Eight fixed offshore jacket platforms with four, six and eight-legged configurations and with K and X type bracings were chosen for this study. Three sets of environmental data for ten, fifty and hundred year conditions covering three regions in Malaysia were selected. Peninsular region was observed to encounter the highest environmental loading of about 21 MN followed by Sabah region with 3.6 MN and Sarawak region with 3.4 MN. The dominant load direction was from North and North East from the open South China Sea. This was logical since most of the fixed offshore platforms in Malaysia are located at about 30 to 150 km distance from shore. Apart from the location, the size, appurtenances and marine growth of the fixed offshore platforms impacted the load. From these findings, engineers can now use different design approaches and redundancy arrangements for the different regions in Malaysia for reducing the cost without compromising the safety of the structure.

Base shear and collapse capacity statistical analysis

As part of structural reliability assessment, the statistical analysis provides engineers with good estimation of distribution and statistical properties for both load and resistance. This study involved modelling of eight (8) offshore structures with the corresponding environmental conditions for ten (10), fifty (50) and hundred (100) years in order to perform non-linear push over analysis for getting the ultimate strength. The environmental condition covers three main oil and gas regions in Malaysia. The collective results of base shear and collapse capacity were used for statistical analysis. The data were analyzed using probability density function with central limit theorem under Gaussian distribution. All the statistical parameters such as mean value (μ), standard deviation (σ) and variance (V) were calculated. The average base shear from the statistical analysis has been obtained as 3.03 MN with a standard deviation of 3.35 and variance of 11.26. For the resistance part, the mean collapse capacity has been obtained as 18.28 MN with a standard deviation of 18.10 and variance of 327.93. This meant that for general case, the structural resistance is higher than the environmental loading. Using probability density function, the reliability index (β) was estimated through robust calculation between statistical parameters of load and resistance. From this calculation, reliability index (β) has been estimated as 3.97.