## 1 Introduction
Currently, except for the linear poro-elastic model, a series of elastoplastic constitutive soil models, such as the Mohr-Coulomb model, Drucker-Prager model, modified Cambridge model, PZIII, etc., are available in FSSI-CAS-2D/3D. The reliability of FSSI-CAS-2D/3D has been validated by an analytical solution and a series of wave flume tests, and it has been successfully applied to the dynamic response analysis and the stability evaluation of breakwater and its seabed foundation under wave/seismic action [10; 19; 20; 21]. However, the coupling model FSSI-CAS-2D/3D cannot perform parallel computation. Correspondingly, the computation scale is severely limited. Furthermore, there is no graphic user interface (GUI) developed for FSSI-CAS-2D/3D. As a result, it is quite difficult to apply to large-scale practical engineering cases. To solve the problems of computing scale and interface operation, [PERSON] and [PERSON] [22] recently developed another coupling model for the FSSI problem based on the open-source software OlaFlow and the commercial software ABAQUS. Since this coupling model makes full use of the advantages of OlaFlow and ABAQUS, it has good reliability and practicability in practice engineering. For the wave-induced dynamics of the jack-up offshore platform, some valuable works have been conducted in the past decade. However, they mainly focused on the following three aspects: (1) The ocean wave-induced impact pressure [23; 24], and the ocean wave and current-induced scouring [25; 26; 27] to the jack-up offshore platform. (2) The dynamic response of the jack-up offshore platform under wave impacts [6; 28]. However, the seabed foundation of the platform was generally deemed as a rigid body, and the effect of the deformable seabed foundation on the dynamics of the jack-up platform was ignored. (3) The effect of the seabed foundation was taken into account, but they mainly emphasized on the bearing capacity of the seabed foundation of jack-up platforms, and the process of the pile penetration [29; 30; 31; 32; 33]. As far as we know, there are few studies on wave-induced dynamic responses of the offshore platform and its seabed foundation adopting a coupled model [34]. However, there are some works that study the dynamic response of a single pile and its seabed foundation to wave impact adopting a coupled model. For example, [PERSON] et al. [35] developed a coupling model combining the wave model wave2 FOAM and the Biot consolidation equation based on the OpenFOAM. Then, they further studied the nonlinear wave-induced dynamic response of a single pile and its linear poro-elastic seabed foundation. [PERSON] et al. [36; 37] investigated the wave-induced response of the seabed foundation near a single pile, where the wave motion was simulated by the CFD software FUNWAVE, and the Biot \"U-W\" equation was taken as the governing equation for the poro-elastic seabed soil. However, these works did not take a fixed offshore platform as the research object. In this study, the coupling model OlaFlow-ABAQUS for FSSI problems newly developed by [PERSON] and [PERSON] [22] is adopted as the computational tool, and a jack-up offshore platform is taken as a typical offshore structure. The dynamic response characteristics of an offshore platform and its seabed foundation under wave impact will be comprehensively studied by a coupled model. The related understanding from the computation results could provide a scientific basis for the design, construction, operation, and maintenance of this type of offshore platform.