In this research a traditional offshore submarine pipeline for the petroleum transportation is under the study. According to the previous studies wave induced forces and the seabed conditions could both cause significant damages on the undersea pipeline system under crucial marine environment. Therefore, based on the available undersea pipeline data and the local ocean environmental conditions around Taiwan, a typical undersea pipeline system of partially suspending and partially sitting on the sea floor is analyzed when subjected to the wave forces. For the inclined suspended part of the pipeline, wave forces calculated from traditional Morison's equation are assumed to apply to the vertical cylinder. Except that, the effect due to horizontal pipelines is also considered for the pipeline partially sitting on the seafloor. By taking into account the tanker motions connected to the pipeline system and the wave forces, the threedimensional dynamic analysis is carried out.
The researches on the offshore pipelines have been carried out intensively due to the exploitation of offshore petroleum, which include the design of the pipeline, the route of the pipeline deployment, construction method and the retrofitting technique on the damaged pipelines. The other tasks for the pipeline design such as the determination of the exerting wave forces, the unsupported span of the pipeline and the techniques for the pipe joints are also equally important. Sunder and Subbiah [1984] compared the design criteria for a few different design-code. Zimmerman [1986] also studied the dynamic behavior of pipelines in deep sea. There are other relevant studies on the offshore pipelines such as the influence of the reaction force from the seabed [Friedmann 1988], the influence of unsupported span on the undersea pipelines [Shah etc. 1988], and the influence of the gap ratio to the liftcoefficient [Lei etc. 1997].
