To address the complex dynamic issues for barges loaded with heavy,high-center-of-gravity and large windward area cargo,such as large steel cylinders,during quayside mooring—including excessive motions,extreme mooring line tensions under effects of wind,wave,and current,a systematic numerical study is conducted.A coupled “frequency-domain and time-domain” approach is employed.A frequency-domain hydrodynamic model of barge is developed in OrcaWave using 3D potential flow theory to obtain key parameters like added mass and wave excitation forces.A fully-coupled time-domain model,integrating the barge,cargo,quay,and mooring lines,is built in OrcaFlex.Simulations are performed for four sea states with varying wave periods and wind speeds.The results quantitatively demonstrate that wave period is the dominant environmental factor governing mooring system safety.Long-period waves are the primary cause of the large-amplitude,low-frequency motions of heavy load barge that induce extreme loads in the mooring system.