ABSTRACT
The structural behavior of floating bridges and breakwaters has been studied to a considerable extent over the last decades for potential applications in civil and marine engineering. In particular, mathematical models and numerical techniques have been developed to properly model and analyze floating structures anchored by cables to the seabed. This includes theoretical studies related to the dynamic response of rigid and elastic floating bodies under arbitrary loadings, as well as experimental testing and drafting of design guidelines for floating bridges and breakwaters under wind and wave loads (Adee 1975, Harms 1979, Yamamoto 1981, Bergan et al. 1985, Williams et al. 1991, Wu & Shih 1998, Watanabe & Utsunomiya 2003, Fu et al. 2004, Watanabe et al. 2004, Shixiao et al. 2005).
The modeling of floating structures often exploits the analogy with a beam on elastic foundation (Bergan et al. 1985, Wu & Shih 1998, Sato et al. 2008). However, geometrical nonlinearities associated with fluid-structure interaction and large displacements are generally not considered. The effects of these nonlinearities are incorporated in the finite element formulation presented in this paper for static analysis of floating structures, with emphasis on floating bridges and breakwaters anchored by cables to the seabed (Bargués 2014). The formulation of a threedimensional beam finite element is developed by taking into account both the nonlinear fluid-structure interaction and the large displacements due to the change of configuration of the anchoring cables. The effects of the nonlinear fluid-structure interaction are evaluated at cross-sectional level by considering arbitrary geometry and loading conditions. The formulation is extended at the structural level based on the principle of virtual displacements to obtain the stiffness matrix and the equivalent nodal force vectors of both the beam and cable finite elements under large displacements. The accuracy of the proposed formulation is validated by means of benchmarks. The effectiveness and applicability in engineering practice of the presented approach is shown through the structural analysis of an existing anchored floating bridge (Lwin 1993) under several loading conditions.
