The offshore wind power industry is the branch of electric energy production from renewable sources which is most intensively developed in EU countries. At present, there is a tendency to install larger-power wind turbines at larger distances from the seashore, on relatively deep waters. Consequently, technological solutions for new supporting structures intended for deeper water regions are undergoing rapid development now. Various design types are proposed and analysed, starting from gravitational supports (GBS), through monopiles and 3D frame structures (jackets, tripods), and ending with floating and submerged supports anchored to the seabed by flexible connectors, including TLP type solutions.
The article presents the results of examination of an untypical large-size gravitational support intended for waters with the depth of up to 40 m. Firstly, a general concept of the new design is presented, while the next basic part of the article describes the support design in detail and provides its strength analysis. The examined support has the form of a large steel container consisting of conical segments. The strength analysis was conducted using the finite element method (FEM), in accordance with the standard DNVGL-ST-0126. Modifications introduced to the most heavily loaded structural node of the support, which was the set of base bottom trusses, is also included. The results of the performed analysis prove that the presented concept of supporting structure for a 7MW turbine meets fundamental strength criteria. The nonlinear buckling analysis was performed to evaluate the critical force acting on the support, which turned out to be 1.44 times as large as the maximum load of the wind turbine. Potentially important issues for further analyses have been identified as those resulting from the asymmetry of basic loads acting on the support.
Numerical calculations of behaviour of ship double-bottom structure during grounding
The idea of the CORET project consists in adding, to the existing construction, special polymer-concrete coatings intended for the increasing of ship's capability against losing structural tightness during collision or grounding. In order to correctly design the protective barriers, to perform relevant numerical simulations is necessary. The elaborating of numerical models of ship structure behaviour during collision is very complicated and requires auxiliary simulations (on submodels) to be performed. This paper is devoted to elaborating a numerical model of a fragment of ship double-bottom structure. On the basis of experimental tests it was possible to verify and calibrate the numerical model which may be used in further design work aimed at the increasing of crashworthiness of structure during collision.
Search for optimum geometry of selected steel sandwich panel joints
Application of steel sandwich panels to ship structures requires many problems to be solved. Joints between the panels as well as those between the panels and other structures is one of the more difficult problems associated with the structures in question. This paper presents the searching for process of optimum geometry of a panel-to-panel joint of longitudinal arrangement, performed by means of the ANSYS software. A configuration was searched for of parameters which can ensure as-low-as possible values of geometrical stress concentration coefficients at acceptable mass and deformations of the structure. Analysis of the obtained results made it possible to propose the optimum geometry of the considered joint.
Like other means of transport, merchant ships face the problem of increasing requirements concerning the environment protection, which, among other issues, implies the reduction of fuel consumption by the ship. Here, the conventional approach which consists in making use of higher strength steels to decrease the mass of the ship hull can be complemented by the use of new steel structures of sandwich panel type. However, the lack of knowledge and experience concerning, among other issues, fatigue strength assessment of thin-walled sandwich structures makes their use limited. Untypical welds imply the need for individual approach to the fatigue analysis. The article presents the effect of numerical FEM modelling with the aid of two-dimensional (2D) and three-dimensional (3D) elements on the results of strain and stress distributions in the areas of toe and root notches of the analysed laser weld. The presented results of computer simulation reveal that modelling of strain and stress states in 2D (instead of full 3D) affects only the results in close vicinity of the notch, and the observed differences rapidly disappear at a distance of 0.05 mm from the bottom of the notch. The obtained results confirm the possibility of use of numerically effective 2D strain and stress state models for analysing the fatigue strength of laser weld according to local approach.