Determination of joint distribution for operating metocean variables for offshore structures

Determination of statistical properties of operating and extreme metocean environmental variables and their interaction with offshore and coastal structures is critical for their design. The mean values of wave height and wave periods increase with increasing intensity of the storm, however, other variables such as wind and current may increase or decrease at the same time. Furthermore, these variables may change their directions during that period and may act in the same or in opposite directions. This paper considers operating conditions of the design of offshore structures. At present design codes recommend three different methods for determination of statistical properties of metocean variables. The most common is based on a combination of metocean parameters estimated from distributions independently without considering any joint probability another one is considering the joint probability of variables and the last one is considering load and resistance both simultaneously. Here in this study, a second option is considered. It is found from the study that we cannot use one method for whole offshore Malaysia but we have to use a combination of methods one and two depending upon location of the site.