| dc.description.abstract | A nonlinear three-dimensional finite element numerical code, called RISER3D, has been developed to perform the static, eigenvalue, and dynamic analyses for slender structures such as beams and marine risers. Distinction with the traditional cubic Hermite finite element method, such as CABLE3D program developed by Prof. J. Zhang and his former graduate students which employed cubic Hermite shape functions, RISER3D adopts quintic Hermite shape functions, six fifth-order polynomials, to interpolate the primary variables including the nodal displacement, slope and curvature. Hence, the new feature of RISER3D program is that it can guarantee the continuity of structure curvatures at the discretized nodes, which can help to make an improvement on the accuracy of numerical simulations. By far, no researcher has ever applied this new numerical scheme to perform finite element analysis for marine risers. Therefore, this dissertation has, for the first time, delved into the new finite element scheme and its application to marine riser problems.
A simplified RISER3D, omitting the axial tension term for riser simulations, can be used to study the static and dynamic problems of Euler-Bernoulli beams which have analytical solutions. Therefore, solving Euler-Bernoulli beam problems, with simplified RISER3D, can not only verify the accuracy and validity of RISER3D, but can also study the effectiveness of the new program by comparing the results to those of by CALBE3D.
Although RISER3D has larger size of element matrices, it shows great advantages over the traditional cubic Hermite finite element method. RISER3D simulation with coarse mesh can produce equivalent accuracy to CABLE3D simulation with fine mesh, which means that it has a faster convergence speed and higher computational effectiveness, which can enhance the confidence for decision makers for the design and analysis of slender structures.
In this dissertation, the validity, accuracy and robustness of RISER3D have been firstly benchmarked with analytical solutions of Euler Bernoulli beam problems. Moreover, they are double checked by making comparisons of the numerical simulation results among RISER3D, Orcaflex, and CALBE3D for marine riser problems. In summary, since RISER3D shows several better merits to traditional cubic Hermite finite element method and its simulation accuracy has been consistently verified by either analytical analysis or Orcaflex, it should be widely utilized for slender structures design and analyses to improve the simulation accuracy and save computational effort. | |
