Submerged floating tunnel(SFT or SFTB,submerged floating tube bridge)is a floating tube bridge,submerged at a defined position under the water level.In this study,four types of SFTs,such as shore-anchored,pier-supported,pontoon-stabilized,and mooring stabilized,are discussed.The main tubular structure of the SFTs can have several cross-section shapes and types,including dividing the carriageways into multiple-tube-system,connected by transversal elements,to provide additional safety in case of fires and operability in case of accidents.Related guidelines for STFs are introduced.The International Federation of Structural Concrete has published,in 2020,a Design Guideline for SFTBs(fib Bulletin No.96)to help the technical community with the design of solutions for SFTBs.The International Tunneling and Underground Space Association has published,in 2023,an Owner's Guide to STFs(Owner Guide)to help the infrastructure's owners to understand when the SFT could be a competitive solution,especially comparing it to traditional tunnel solutions.Currently,the Norwegian national standards have been the first to include this structure in the bridge national handbook(2020).Furthermore,21 cases/studies/designs/proposals of STFs are listed and the hot topics,including fluid structure interaction and impacts,are briefly introduced.The SFTs can reduce the main sea loads on the structure,the slopes of the tunnel and the connected structures,the length of the crossings,the disturbance to the undersea landscape,and the acoustic impact in the surrounding area.It is concluded that the growing attention on the topic of environment and the possibilities given by recent materials and technologies in reducing the climate impact will hopefully represent a new era of possibilities for the diffusion of this clever structure.
关键词
水下悬浮隧道/水下悬浮管桥/指南/流体-结构相互作用/荷载/冲击/支撑形式
Key words
submerged floating tunnel/submerged floating tube bridge/guidelines/fluid structure interaction/load impacts/support form
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