Esmaeil Zavvar - Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
Hamid Ahmadi - Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran

Until now, offshore steel platform structures have used for exploration of gas and oil to meet energy requirements. Structural platforms are fabricated from Circular HollowSections. In particular, circular hollow sections have proved to be suitable for structural elements. Due to their shape, circular hollow sections have low drag coefficientsand therefore are the most favorite choice for elements subjected to the wind and wave loading. Thanks to low cyclic loading, they are susceptible to fatigue damage.Tubular welded joints have more complex geometry than other plated joints. Due to the variety of geometries that tubular joint may have, the classification approach isnot useful for the design of such joints. One approach, for designing weld details from the viewpoint of potential failure from the weld toe, is the so-called hot-spot stressmethod [1].