Spanning Submarine Pipelines Dynamic Response Analysis And Vibration Control Theory

Submarine pipeline is a subdivision of the lifeline engineering. Because of the bad condition around the pipeline and the complication of the boundary condition, the security of the submarine pipeline is in threat. One of the two problems is the failure of pipeline strength in seismic load; the other is the fatigue due to vibration of suspended pipeline in the lift forces. As a result, it is important to compute the response due to earthquake and lift forces, to put forward the methods of controlling the vibration of ~he free spanning. A model which considers seismic wave propagation from one end to the other end is established to analyze the response of free spanning submarine pipelines under seismic input at the twos ends. Many examples are employed to analyze dynamic stress and displacement response for various spans. Therefor, the following conclusion can be drawn that the response of pipeline is closely concerned with the frequency of seismic wave and that the free span can be obtained by the frequency of the suspended span. The other model is founded for the response of free spanning submarine pipelines due to the lift forces, and a fatigue assessment process is expounded in detail. The response of the suspended span and the elements affecting the response are discussed, and the accumulated fatigue damage is computed. The Rayleigh damping that is introduced in solving the above two equations is greatly simplified the solving process. The results indicate that controlling the length of the free spanning is the key to control the vibration of the suspended span. Finally, a new concept that is divided into three paces and two levels is put forward controlling the free spanning. The second spanning is rightly the critical length needed controlling, besides that two methods to control the span are discussed.