Immersed tunnels are positive buoyant structures during installation and negative buoyant after installation. A tunnel is composed of sequential immersed elements that are coupled to each other in joints. Tunnel elements consist of segments which are compressed to each other by longitudinal post-tensioning. After immersion the tunnel is supported by the seabed and the longitudinal post-tension is cut at the joints between segments. Therefore, the structure is a segmented lining which is sensitive for settlements due to non uniform circumstances over the length of the tunnel. An uneven response of the bedding underneath the tunnel introduce shear forces in joints of an immersed tunnel. Because immersed tunnels need to be buoyant during installation, they have limitations on weight and geometry, the size and therefore the capacity of these shear keys is limited because the height of the tunnel, as shear keys are applied in the walls of the tunnel. The foundation response is influenced by many factors related to subsoil but also to construction and dredging tolerances. The shear forces were derived as a function of different covariance lengths for subsoil stiffness and dredging tolerances for different tunnel layouts. In reliability analyses, using two different probabilistic methods, exceedance probabilities of maximum shear forces are derived for one lay out using Non Parametric Bayesian Networks and Vine Copulas. The analyses give more insight in to the magnitude of the shear forces in joints both in conditioned and unconditioned situations and this can be used for the design of immersed tunnels.

Vine copulas have become the standard tool for modelling complex probabilistic dependence. It has been shown that the number of regular vines grows extremely quickly with the number of nodes. Chimera is the first attempt to map the vast space of regular vines. Software for operating with regular vines is available for R, matlab and Python. However, no dataset containing all regular vines is available. Our atlas of regular vines, Chimera, comprises all 24 4 × 4 matrices representing regular vines on 4 nodes, 480 5 × 5 matrices representing regular vines on 5 nodes, 23,040 6 × 6 matrices representing regular vines on 6 nodes, 2,580,480 7 × 7 matrices representing regular vines on 7 nodes and 660,602,880 8 × 8 matrices representing regular vines on 8 nodes. Regular vines in Chimera are classified according to their tree-equivalence class. We fit all regular vines to synthetic data to demonstrate the potential of Chimera. Chimera provides thus a tool for researchers to navigate this vast space in an orderly fashion.

A submerged floating tunnel (SFT) is a structure that has been proposed as an innovative solution for waterway crossings around the world. However, to this day, no SFT has been constructed yet. One of the main reasons is that there is an insufficient insight into the structural reliability of the SFT. Here, a method to assess the expected structural response of an SFT under traffic loads and a reliability assessment of the results is presented. To do this, traffic models and structural response and reliability are coupled. The methodology presented herein proposes an innovative way to combine copula-based models and structural models to obtain more a more realistic structural response of the SFT. The focus will be on one failure mechanism, leakage caused by bending failure of the SFT in the longitudinal direction. The method utilizes a copula-based model to characterize the traffic loads and simulate traffic loads on the SFT (axle weight, inter-axle distance, and inter-vehicle distance). Next, a structural model is used to assess the structural response and derive stresses. Using a probabilistic analysis, the design of the cross-section can be adapted so that it meets the requirements for leakage caused by bending moments. For the case study is demonstrated that for a buoyancy weight ratio (BWR) of 1.1 an optimal design can be achieved based on a probabilistic method. This methodology could be extended to other failure modes of an SFT or to other structures.

The Submerged Floating Tunnels can be applied in crossings with large depth and/or large widths, it might be one of the few options left to build a fixed link between two shores. The Submerged Floating Tunnel is not a typical and traditional structure as it could not be identified as a pure civil structure. It also has components of other fields of application such as off-shore structures (platforms), naval structures (ships and submarines) and marine structures (breakwaters) that use different approaches to derive a target reliability for the design. In this paper, the reliability approach of the different fields of applications are examined and combined to find a specific target reliability approach for Submerged Floating Tunnel structures. Not only structural reliability is considered but the identification of acceptable risks with respect to life and economical consequences are taken into account. This is done by reviewing literature and guidelines on target reliability in aforementioned fields.