3-D Responses of Vertical Pipe Bottom Pin-Joined to Horizontal Pipe to Ship Motion and Thrust on Pipe - Part II: Comparison of MSE and FEM Results (A)

摘要

The present entire pipe system consists of a very long vertical pipe with elastic joints, pin-joining the buffer (mass) at the pipe's bottom end to a much shorter horizontal pipe. The opposite end of the horizontal pipe is pin-joined to a vehicle maneuvering in the planar (x, y) seafloor. The seafloor vehicle can restrain the motion of the horizontal pipe. This requires more elaborate computational modeling of the entire pipe system than for the vertical pipe alone. The joints on the entire pipe were modeled previously in Part I by 2 methods: (a) the mass-spring elements (MSE) and (b) finite elements (FEM). Because the entire pipe system has one zero eigenvalue associated with the rigid-body mode, the zero-eigenvalue problem is solved with the shift technique. The weight, generating the internal axial force of the vertical pipe, influences the eigenvalues of the entire system. Based on both the present static analysis and eigenvalue analysis, it can be stated that MSE is simpler and gives better computational accuracy, than FEM. The accuracy and advantages of the MSE modeling over FEM are clearer for the entire pipe system than for the vertical pipe system alone.