Abbas Yeganeh Bakhtiyari - Assistant professor
Abbas Ghaheri - Associated professor
Reza Valipour - Graduated student

Free spanning phenomenon in known as a very common problem for unburied offshore pipeline. Free spanning can influence the total safety of the multi-span pipeline; hence over the uneven seabed conditions the evaluation and its effect become crucially important. Different criteria are proposed by different codes to limit free span to allowable length, however all the effective parameters on determination of allowable free span length have not been considered. Therefore, the assessment of soil boundary condition on determination of pipe allowable free span length is significantly essential in this paper, the effects of soil boundary conditions on the offshore pipeline natural frequency have4 been assessed in order to have a useful criterion to determine pipeline allowable free span length. It is also intended to propose a rational criterion for designers to select the best rout for offshore pipeline to reduce free span effect.

Offshore Pipeline , Free span , Soil boundary condition