Design of an Offshore Tripod Structure for MET/OCEAN Research

摘要

This paper describes the design and construction of a steel pipe pile tripod structure for the support of meteorological and oceanographic (MET/OCEAN) instrumentation. The structure, known as the air-sea interaction tower (ASIT), is located approximately one and one half nautical miles south of Martha’s Vineyard, Massachusetts in approximately 15 meters water depth and supports a MET mast that rises to 20 plus meters above mean sea level. Design criteria included minimizing flow disturbance and vortex induced vibrations (VIV) due to the moderate to strong tidal currents. This was considered critical due to the sensitivity of the instrumentation both above and below water. Minimizing cost and rapid deployment time were also critical design considerations. The ASIT was designed for a nominal design life of 5 years that could be extended to 10 years if project funding were continued. Therefore, selection of appropriate design environmental conditions as well as corrosion protection and future dismantling issues were also given special consideration. rnThe utility and general design aspects of tripod structures and the analysis of slender, flexible pile structures subject to VIV are emphasized herein. Such structures may have many useful port and harbor applications such as the support of navigation aides and communications/data relay towers, guide piles/dolphins and other such isolated structures where minimal; structure, cost and construction time are of prime importance.