Design and Construction of a Flexible Layberth Facility to Withstand Severe Weather Forces

摘要

In May 2012, the U.S. Maritime Administration (MARAD, Owner), a department of the USDOT, embarked on a major capital project to design and construct a permanent layberth facility to consolidate several of the nation's Ready Reserve Fleet of reduced operating vessels at one facility. Tasked with providing roll-on/roll-off capable docks with hurricane level moorings, the design-build team delivered a layberth facility for eight (8) vessels in four (4) berths. Unique aspects of the project included a requirement to provide safe long-term berthing for four (4) large, medium-speed, roll-on/roll-off (LMSR) vessels and four (4) other roll-on/roll-off transport vessels, nested in pairs, and which are to remain at berth during Category 1 hurricane forces. This paper focuses on the challenges to design, permit, and construct such a robust facility, as well as accommodate the Owner's desire for flexibility to berth a wide range of vessels, with different hull geometries, draft depths, and roll-on / roll-off ramp locations. The solution developed for this project utilized a combination of flexible moorings and fixed structures; typically deployed where vessel movement is less restricted, flexible moorings consist of buoy-supported chains or wire rope connected to steel plate or pipe pile anchors. This innovative design allowed the facility to be constructed on an extremely limited federal budget. The design-build team was able to deliver a turn-key facility that provided dedicated berths for specific vessels which had been earmarked for the facility, with the ability to expand in the future to allow for further versatility. The design-build team modeled the facility and located the berthing and unique anchor mooring structures to support dedicated berths for the current project and located such to allow for their functionality with different vessel arrangements for future construction. Upon completion of the project a report was provided which detailed specific components (berthing structures, anchor mooring structures, fender elements, etc.) for each type of vessel that could potentially be berthed at the facility. This report also contained budgeting costs for these components in today's dollars so that the Owner could budget for growth accordingly in future time periods.