Cost-optimized Design of Tubular Steel Towers and Offshore Support Structures

摘要

Steel support structures(towers,monopiles,etc.)are among the most costly components of wind turbines.As a consequence,all efforts have to be made to use cost-optimized solutions for specific wind turbines and environments.Especially,increasing hub heights and installation in deeper water pose high demands on support structures.For onshore application and hub heights beyond 100 m,the tower frequency becomes a major cost and design due to the logistic restrictions in tower diameter.Likewise for offshore wind turbines on monopiles the vibration frequency is largely determining the design.In this paper we describe a systematic approach to tower design and,more general,steel support structures taking into account all necessary static and dynamic requirements.With our method it is possible to find the minimum structural mass under a variety of constraints,among them maximum allowed diameter for transportability,available sheet thicknesses,shell buckling utilization of the steel,fatigue category of weld seams,vibration modes,brittle fracture and vortex induced vibrations.Calculations are done according to Eurocode 3.Further the soil structure interaction can be taken into account for raft foundation as well as for monopiles(p-y-curves).Based on the algorithms described above a computer program for the fast design of optimized steel tubular structures was developed.The program allows for quick determination of the cost-optimized tower shell and flanges(geometry and number of bolts).