Strengthened T-mooring design of self-propelled deck barges under open wharf conditions and its applicable metocean conditions

With the rapid expansion of ultra-large industrial modular units (ULIMUs), the demand for maritime transport has grown substantially. These units are typically loaded via roll-on/roll-off (Ro/Ro) operations using ship T-berthing at factory-owned wharves. However, such wharves are often shallow and exposed, subjecting vessels to significant windage and environmental forces. Conventional T-mooring systems (CTS) frequently fail to meet the stringent motion limits required for safe Ro/Ro loading and are prone to mooring line failures. To address this, a strengthened T-mooring system (STS) is proposed. Two supplementary mooring chains are symmetrically added to the bow beyond the CTS. Numerical simulations were first conducted to comparatively analyze the dynamic performance of the CTS and STS. Then, based upon the PIANC criteria for ship motions and the OCIMF guidelines for mooring line strength, the applicable sea conditions for the STS were concluded for both Ro/Ro operations and in-port periods. Finally, the field measurements were utilized to validate the numerical simulation. Results show that the STS significantly reduces surge, sway, and yaw motions and peak mooring-line tensions by up to 70%. These findings demonstrate that the STS provides enhanced stability, improved load distribution, and superior operational safety under exposed open-wharf conditions.