## 1. chinaXiv:201712.02141 [pdf]

 A time domain method is developed for estimating the transient response of very large floating structures under unsteady external loads. The hybrid frequency-time domain approach based on Cummins equations is adopted. First, the discrete-module-beam-bending-based hydroelasticity theory in which a flexible structure is discretised into several rigid submodules connected by beam elements is used to establish the equations of motion for a flexible structure in frequency domain. The equations of motion in frequency domain are transformed into time domain following the idea of Cummins equations. The unsteady external loads at any point of the flexible structure are transferred to the centre of gravity of each submodule using the hydrostatic analysis of a beam in calm water. Good agreements are obtained between the numerical and experimental data for a weight drop test and a moving point load test of a continuous flexible structure in calm water, which validates the present time domain method. Finally, the time domain method is used for simulating the transient response of an interconnected flexible structure under the combination of wave and unsteady external loads, which highlights the significant effects of moving point loads on both the vertical displacement and bending moment of the structure.

## 2. chinaXiv:201706.00364 [pdf]

 The hydrodynamic problem for multi-body systems in waves has complexity in both wave structure interaction and coupled dynamics with interconnection. A consistent approach is developed for calculating the dynamic response of multi-body floating systems. This method is based on multi-rigid-body hydrodynamics and Euler-beam bending theory and can be used to deal with rigid or flexible multi-body floating systems in both frequency and time domain. Within the framework of this consistent approach, a stiffness approximation method is proposed to calculate the natural frequency and corresponding oscillation mode of a hinged multi-module structure. This is significant for both traditional multi-body floating system (for the purpose of structural safety) and wave energy converters (for the purpose of power efficiency). The hydroelasticity theory proposed by Lu et al. (2016), which is used to deal with continuous flexible structures with cross section of simple shapes, is extended to be applicable for multi-module flexible structures with cross section of arbitrary shapes and varied geometric features in longitudinal direction. Finally, an effective strategy is established to analyse in time domain the dynamic response of a hinged multi-module flexible structure with moving point loads on the upper surface in waves, representative of vehicles moving on a floating bridge or airport.

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