Development of dynamic simulation method for floating bridges subjected to wind and wave loadings

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The objective of this research is to develop a method for prediction of dynamic response of a floating bride subjected to wind and wave loadings where the following three items can be considered at the same time 1) elastic deformation of the superstructure, 2) frequency dependence of the hydrodynamic forces, and 3) nonlinear restoring force characteristics of the mooring system. In order to realize such a methodology, the following procedure has been implemented: 1) the super-structure of the floating bridge is modeled by Finite Element Method (FEM; NASTRAN is actually used) and the hydrodynamic force characteristics including frequency dependency is modeled by added-mass and damping characteristics defined at the nodal-points of the floating foundations, 2) in the modal-coordinates, the memory-effect function of the frequency-dependent hydrodynamic force and the nonlinear restoring force characteristics is solved by Newmark-β method.Then, the development of a computer program for prediction of dynamic response of a floating bridge subjected to irregular waves in the time domain has been made. In this research, the floating bridge with separate-type floating foundations is considered. The floating foundations are modeled as rigid-bodies, each of which having six degree of freedoms, and the super-structure, which connects the floating foundations, is modeled as linear elastic-body. The mooring systems are modeled as springs having nonlinear restoring force characteristics. Because of the frequency-dependence of the radiation wave forces, the memory effect has been taken into account in the time domain. The methodology of the developed program is presented with several numerical examples for a typical floating bridge with separate-type floating foundations.