The Norwegian Public Road Administration is planning to upgrade Coastal Highway E39 by replacing ferry connections with floating bridges or submerged floating tunnels (SFTs). This study considers a potential pontoon-supported curved SFT designed for crossing Sognefjorden at a submergence of 12 m. It consists of two identical tubes with a diameter of 12.6 m each in a tandem configuration and with a length of approximately 4 km. The natural frequencies of the low-order modes are well within the energy content in the spectra of the second-order difference-frequency wave excitation forces and the vortex shedding-induced forces. In this paper, numerical simulation of wave-induced hydroelastic response and flow-induced vibrations of the twin-tube SFT is performed. Long- and short-crested waves, the first and second order wave loads, are considered. A time-domain approach to simulate crossflow vortex-induced vibration (VIV) and VIV-amplified inline drag forces, partly based on the coefficients obtained experimentally, is established and applied. The focus is on extreme conditions – relating to ultimate strength limit states. The second-order wave load substantially affects the lateral motion and lateral bending moment, as expected. The short-crested waves influence the response in both the lateral and vertical directions by exciting asymmetric eigenmodes. In strong flow conditions, once VIV is excited, the standard deviation of the vertical motion (of about 30% of the diameter) and the bending moment about the horizontal axis is more that an order of magnitude larger than that induced by the wave loads. The simulation of the wave- and flow-induced load effects provides a good reference for the design of SFTs.

挪威公共道路管理局正计划通过用浮桥或水下浮动隧道 (SFT) 取代渡轮连接来升级 E39 沿海高速公路。本研究考虑了一种潜在的浮筒支撑弯曲 SFT，其设计用于在 12 m的淹没位置穿越松恩峡湾 。它由两个相同的管子组成，每个管子的直径为 12.6  m，串联配置，长度约为 4  km。低阶模式的固有频率完全在二阶差频波激发力和涡旋脱落诱导力的谱中的能量含量之内。在本文中，对双管 SFT 的波浪引起的水弹性响应和流动引起的振动进行了数值模拟。长波峰和短波峰，一阶和二阶波载荷被考虑在内。建立并应用了一种时域方法来模拟横流涡激振动 (VIV) 和 VIV 放大的直线阻力，部分基于实验获得的系数。重点是极端条件——与极限强度极限状态有关。正如预期的那样，二阶波浪载荷显着影响横向运动和横向弯矩。短波峰波通过激发非对称本征模式影响横向和垂直方向的响应。在强流动条件下，一旦 VIV 被激发，垂直运动的标准偏差（约为直径的 30%)并且绕水平轴的弯矩比波浪载荷引起的弯矩大一个数量级。波浪和流致载荷效应的模拟为SFTs的设计提供了很好的参考。