Increasing numbers of subsea structures related to wells and pipelines are being placed on the seabed as part of typical subsea or tie-back developments. Given the proliferation of these structures and the marginal cost of offshore developments, controlling installation and fabrication costs for subsea structures can be key to project viability. Skirted mudmats are often the most cost-effective foundation type, and particular additional design focuses on optimising their cost by minimising foundation weight and installation time. Subsea foundations must be designed to withstand all applied loads during their design life (e.g. during set-down, tie-in, hydrotest, operation etc.) with suitable reliability. Using skirts, peripheral or internal, to improve the sliding resistance is an efficient solution provided the self-weight of the subsea structure on set-down is sufficiently large to ensure installation of the skirts (even for the strongest likely seabed conditions), but can lead to significant cost increases if additional ballast is required to ensure this. The paper examines how foundation skirt geometries can be optimised in order to provide sufficient foundation in-place capacity whilst minimising the amount of self-weight required for their installation. Parametric studies are presented that show how the sliding capacity of individual skirts is affected by the weight of the structure, and also the spacing and position within the foundation plan.

This paper is aimed at investigating the influence of load-bearing style on the mechanical behavior of anisotropic engineering materials. The study on elastic constants and failure forms of materials will be presented under different loading condition. Firstly, the mechanical properties of unidirectional holey laminated materials are discussed based on the uniaxial tensile tests. The equivalent elastic modulus, Poisson’s ratio and shear modulus are obtained, and the pattern and mechanism of failure are analyzed. Then, the biaxial tensile tests are carried out for PVC orthotropic membrane materials with different stress ratio between the warp and weft direction. A comparison of limit strengths under biaxial loadings is given with that in uniaxial loading case. Finally, the dynamical behaviors of shape memory alloy (SMA), iron wire, and rubber composite as well as compound rubber are studied respectively by impact-tension tests. The failure forms, energy dissipation ratio and impact-tension toughness of materials are analyzed. It is shown that the mechanical properties and failure pattern of anisotropic materials have much to do with the load-bearing styles. It agrees well with actual properties of anisotropic material used in engineering structures.

This paper presents an approach to investigate the mechanical properties and failure patterns of shape memory alloy (SMA) by experimental methods. Tests were carried out under the conditions of uniaxial tension, cycling loading and impact-tension respectively. The mechanical behaviors of NiTi SMA such as the relationship of stress-stain, super-elasticity, high damping, energy dissipation and tension-shock toughness are discussed in detail. In addition, the destroy patterns of SMA materials are analyzed for varying condition of testing. Whether ductile failure or brittle fracture is decided to do much with the testing styles and strain rate of materials. It is shown that with the large restoring deformation, higher energy dissipation factor and tension-shock toughness, so NiTi SMA structural functional materials are very suitable for vibration control in engineering.

A dynamic model of vehicle-bridge interaction is presented considering the railway vehicle moving through bridge with varying velocity. Assuming the vehicle has a constant acceleration, the motion equations of coupled vehicle-bridge system were deduced based on DAlemberts principle and theory of Euler beam. Dynamic responses of system were analyzed both cases of the acceleration and drag acceleration for a moving car. Results show that the amplitudes of vibration of the system will enlarge sharply with the acceleration of vehicle increasing, and the maximum of responses occur when the vehicle moving at the middle point of bridge. In addition, the stiffness coefficient is one of the key factors to affect on dynamic responses of system. Generally, the suitable rigidity of structure is much important to decrease the responses and suppress the vibration of system.

In this paper, a hybrid approach is presented for modeling the stratum disturbance during the shield construction in water-rich soil. The disturbance mechanism of stratum is analyzed based on the theory of shield excavation. The deformation and settlement of ground surface are simulated by three-dimensional finite element method. Some physical properties and displacements of soil layers are measured by site survey method. The transverse settlement trough of tunnel is a normal distribution curve and the largest displacement to happen on the above of excavation face. There is also an important influence of shield tunneling on the ground settlement in the longitudinal profile, but this effect disappears a certain distance apart. It is shown that the results based on the numerical simulation and the data from site survey in this work are much rational.