The European highway E39 ferry-free Project led by the Norwegian Public Roads Administration (Statens vegvesen, NPRA) is in its full momentum on solving the technological challenges to cross the deep (up to 1350 m) and wide (up to around 6 km) Norwegian fjords. Different types of crossing solutions have been explored up to now. The current paper is related to the submerged floating tube bridge (SFTB) solution. But the model itself can be applied to any other structure that may experience loads induced by a passing vessel. The method of Xiang and Faltinsen (2010) for evaluating the calm water interacting loads between two vessels up to the point of collision has been extended to include an SFTB. Equations of loads are extended to include also the vertical load and pitch moment on the body in question. The vertical load induced on the SFTB is investigated for the purpose of identifying the significance of this effect on the design. The investigation includes this effect under different maneuver scenarios of the passing vessels: a single ship passing, two ships advancing in side-by-side positions, encountering or overtaking maneuvers. In addition, parametric studies on the submergence of floating tube bridge, and vessel speeds are studied to get more understanding of this effect. A simple exercise shows that it is worth of further investigation on ship-induced surface waves effects on the structures in vicinity of the ship path. Finally, the evaluated loads are compared with other types of loads from the analysis results of the on-going NPRA SFTB design.
<p>A submerged floating tube bridge (SFTB) is a bridge hidden below the water surface and thus, able to preserve the landscape and to lower the noise impact on the fjord environment. A twin tube STFB with a main span of 5100 m has been proven to be a feasible, robust, safe and competitive solution to cross the Bjørnafjord.</p><p>Horizontal stability is ensured by the use of a space frame structure between the tubes, resulting in beam-like construction. Two alternatives have been proposed for the vertical stabilization: tension leg tethers or floating pontoons. The design has undergone rigorous response analyses, proving that the concept has a low sensitivity to changes in the design or the environmental loads. Collisions of submarines on the main tubes or tethers has been evaluated, together with the possibility of a collision of a ship on a pontoon. Fires and explosions have been assessed thoroughly, considering the safety procedures from the preliminary design of the structure.</p><p>The necessary marine operations for the installation phases have been detailed and the serviceability life for the structure has been analysed together with the maintenance for a safe and robust design.</p><p>The adaptability and robustness of the structure to the site recalls to the possible application for international similar crossings and the structure shows a high potential in the pre-casting field.</p>
<p>The present paper focuses on dynamic action challenges for Submerged Floating Tube Bridges (SFTB) over longer spans. Response analyses have been performed in time domain for a tether concept and a pontoon concept, respectively, using 3Dfloat software. Natural periods are compared with an analytic approach. Vertical displacements and accelerations are taken out for different swell and wind generated sea load cases.</p>
A submerged floating tube bridge (SFTB) concept has been developed for the Bjørnafjord crossing. Two designs are currently considered feasible: pontoon stabilized and tension leg stabilized SFTB. Previous studies have found that the vertical motions and accelerations are largest for the pontoon stabilized concept, although both designs are within the requirements. With respect to ship impact, seabed mooring is favorable. No ship impact is likely at the current depth of the bridge, and this is considered a great advantage. Submarine impact on the tethers must be considered, however. Using a failsafe link between the pontoons and the tube itself significantly lowers the stress in the bridge due to ship impact. The link will break at impact energies above a given threshold, and release the pontoon. The bridge is designed to survive loosing one pontoon. It is seen that the bridge survives impact even without the failsafe, thus it is not a critical element, but the stress reduction is beneficial. The cost of the tension leg moored alternative is substantially higher than that of the pontoon stabilized one. Both concepts are considered feasible, but the final decision depends on more accurate knowledge of the soil conditions in the fjord.
A proposal for a Submerged Floating Tube Bridge as part of a scheme for a new and improved fixed link along the E39 route, across the Bømlafjord in Norway, is presented.<p> The existing crossing is not able to satisfy the previsions of the increase in traffic and the new rules on the road alignment and gradient. The new requirements, including the need of a carriageway with two lanes for each direction, imply a complete replacement of the existing tunnel with a longer one. The possibility to substitute the new bridge, necessary for the northern part of the crossing, with a SFTB (Submerged Floating Tube Bridge) allow to reduce the parts of the tunnel in the southern part that have to be substituted. The advantages of the proposed scheme for the crossing are evaluated and discussed. A comparison, in terms of costs, of the different solutions for the design is presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.