Mohamad Javad Ketabdari - Amirkabir University, of Technology, Tehran, Iran
Saeed Jabbari - Hormozgan University, Bandarabbas, Iran

Jack-up platforms can experience different environmental situations according to their transport possibility. At the beginning these platforms were used as mobile docks [1] and then as drilling platforms for shallow waters. Time domain approach is mentioned as the most accurate method despite of its difficulties. While frequency domain methods usually are applied on simplified and linearized models. A frequency decomposition of wave forces on the structure shows that even for a regular wave, supper harmonics exist [2].