Development of a coupled time-domain model for complexly moored multi-body system with application in catamaran float-over deck installation

• A coupled time-domain model is developed for simulating multiple floating structures, with a specific focus on catamaran float-over operations. • Adopting a state-space model enables fast and accurate predictions of the multi-floater system's dynamics. • The model shows good agreement with AQWA in simulating the dynamic behavior of the Kikeh Spar float-over installation. • The adaptive time step integration algorithm shows priority in capturing the occurrences of impacts and separations during the mating stage. Multiple floating structures offer a versatile solution for offshore engineering. However, these systems are inherently complex due to hydrodynamic interactions and intricate connections between structures and moorings. This study aims to develop a coupled time-domain model for multiple floating structures, and to demonstrate its application to catamaran float-over operations. The developed model is validated against AQWA using a catamaran float-over installation of a Spar platform as a benchmark case. Results indicate that adopting a state-space model enables fast and accurate predictions of multiple floating structures. Additionally, it is observed that iterative algorithms significantly influence the prediction of impact dynamics when impacts and separations occur alternately. The developed model exhibits good agreement with AQWA in forecasting the kinematics and impact forces of the catamaran float-over system, confirming its reliability for simulating multiple offshore structures.