Sensitivity Analysis of Wave Forces on Monopod Platform under Metocean Condition by Simulation

Stokes wave theory for deep water condition is employed in PETRONAS Technical
Specification (PTS) for all water condition in Peninsular Malaysia Operation,
Sarawak Operation and Sabah Operation. This research aims to address this through
predicting wave forces from wave theories using simulation study and analyzing the
sensitivity of wave forces to wave theories and deviated wave height criteria. In PTS,
for 100-year storm event, the wave height criteria recorded shows fluctuation of
140% from the wave height criteria for operating event. With reference to this, it is
feasible to adopt a deviation of ±40% with assumption that the wave height is
reduced to 40% less is during the extreme low tidal waves. Wave theories are used in
theoretical predictions of wave kinematic using the measured wave height, wave
period and water depth. Extensive literature review has been done to better
understand the wave forces, water condition and prediction wave kinematics by wave
theories. Structural Analysis Computer Software (SACS) v3.5 is used as the main
tools in the methodology. The monopod structure is modeled in SACS for PMO,
SKO and SBO region. Stokes wave theory is identified as conservative for monopod
structure design in PMO zone. For SKO zone, the wave force is recognized as
sensitive towards wave theories. Based on analysis result, Cnoidal wave theory is
identified as conservative over other applicable wave theories. Samarang in SBO
zone is having transitional water condition. Wave force is recognized to be changing
sensitively by Cnoidal wave theory. Analysis results reflected that Cnoidal is more
conservative due to more critical values of wave forces predicted, higher order wave
theory and best describe the transitional water condition.