Mahmood Reza Akbarpour-e-Jannat - M.Sc. Student of Marine structures Sahand Univ. of Tech
Ahmad Reza Gharabaghi - Assistant Professor Sahand Univ. of Tech.
Mohammad Reza Emamai - Assistant Professor Sahand Univ. of Tech.

In the recent decades, the fatigue analysis and design of tubular joints has been one of the main concerns of the Offshore industry, researches and Engineers, A reliable design of a jacket type platform would depend larglly upon the strength if iits tubular joints. According to these studies, the important reason for fracture in marie structurse is related to the fatigue and orrosion at tubular joints. Gradual development of imperfections at steel connections due to cyclic loads such as wave forces will result in fatigue. Although here are some effect in fatigue behavior of structures,like forces exerted during construction and transportation however, the fatigue subjected due to waves is more important than the other. In this paper a rypical jacket platform which is erected in the persian Gulf is selected and analysed by available version of ANSYS software. The time history of axial forces at a critical connection is calculated by a dynamic analysis. then that connection is simulated by 4-node shell elements. A refine mesh is selected by doing a simple test compared with the available experimental results. Finally the fatigue usage factor critical connection is obtained.