Ultimate strength of ship structures including thermal and corrosion effects: a time variant reliability based approach

On December 17th 2002 the World Meteorological Organization issued a statement according to which the global mean surface temperature has risen and consequently 2002 was the warmest year in the 1961-2002 period.  Positive sea surface temperature anomalies across much of the land and sea surface of the globe in general contributed to the near record temperature ranking for the year along with climate anomalies in many regions across the globe.  Climate change as a result of global warming is a worldwide occurring phenomenon which the experts have only recently started to understand and which affects and significantly will affect us in the near future.  The effects of climate change have been somehow neglected by the ship and offshore related academic and research communities. In the case of thermal effects on ships structures, unless the problem solved is temperature dependent, this type of stress has often been neglected and not been taken into account in most types of analysis.  The most likely reason behind this would seem to be that the stresses produced from temperature changes would be too small to be taken into account compared with still water loads or wave bending stresses.  This is not the case though.  Records exist of ships having broken in half while moored in still water and major hull factures occurred in still water while the temperature was changing as it can be seen from the relevant published literature.  Very little work on thermal stress on ship structures has been published since the 1950s and 1960s and no work has been done that considers temperature effects on ultimate strength. Research undertaken aims to incorporate temperature effects on existing ultimate strength formulation by using a thermal stress approach, compare and use recently proposed corrosion models to model corrosion effects on ultimate strength and provide a foundation on which reliability analysis could then be performed for Tanker/FPSO structures operating in the North Sea.  After comparing a number of possible approaches that would enable to loading components to be combined in a stochastic fashion, the loading part of the reliability analysis is handled using extreme wave statistics and the Ferry Borges-Castanheta load combination method. Annual reliability indices and probabilities of failure are calculated for hogging and sagging conditions using both time-variant and time-invariant approaches and a variety of reliability analysis approaches showing the effects of temperature along with partial Safety Factors for all variables taken into account

Application and analysis of stiffened side shell panel failure for naval patrol craft

Thesis (S.M. in Mechanical Engineering and Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 173-176).Over their lifetime, naval patrol craft are subjected to many different types of loading scenarios, most of which are perfectly safe. In rare instances, through a variety of different reasons, these craft are loaded beyond their means, resulting in structural failure. This thesis focuses on how side shell stiffened panel failure occurs from a global and local perspective, bridging the gap between a real life problem and mechanics theory in an effort to reduce uncertainty in the ship structural design and construction process. It incorporates aspects of basic ship structural design theory, detailing static and dynamic shipboard loads, progressive collapse behavior, and global causes of hull strength reduction. Locally, it examines stiffened panel failure modes due to axial loading through a comparison analysis with consideration for sources of panel strength loss. Finally, this thesis discusses methods for avoidance and mitigation of failure in the future at the design, construction, and operational levels. On the global level, this thesis draws from two incidents in the last decade where U.S. Navy and U.S. Coast Guard patrol craft have had class-wide incidents of structural failure. These failures have ranged from buckling, to yield, to fracture. Each ship's background is discussed, and primary stress calculations are presented with design margins based on classification societies, along with an engineering analysis of the failures that occurred on each vessel. Internal and external factors for overall hull strength reduction are examined and applied to each case, including considerations for slamming and saltwater corrosion.(cont.) Using one of the failure incidents that took place on the U.S. Coast Guard 123', local failure modes are examined across several analysis methods for axially loaded panels. Buckling and ultimate load values are calculated through a parametric design space, while boundary conditions and geometric properties are varied. Finite element analysis and proven analytical methods are used, including those developed by Von Karman. A comparison analysis is completed using experimental data, where local causes for strength reduction in panels are considered, including construction imperfections, shearing, residual stresses, cracking, and initial deflection.by Matthew K. A. Mothander.S.M.in Mechanical Engineering and Naval Architecture and Marine Engineerin

5th International Probabilistic Workshop: 28-29 November 2007, Ghent, Belgium

These are the proceedings of the 5th International Probabilistic Workshop. Even though the 5th anniversary of a conference might not be of such importance, it is quite interesting to note the development of this probabilistic conference. Originally, the series started as the 1st and 2nd Dresdner Probabilistic Symposium, which were launched to present research and applications mainly dealt with at Dresden University of Technology. Since then, the conference has grown to an internationally recognised conference dealing with research on and applications of probabilistic techniques, mainly in the field of structural engineering. Other topics have also been dealt with such as ship safety and natural hazards. Whereas the first conferences in Dresden included about 12 presentations each, the conference in Ghent has attracted nearly 30 presentations. Moving from Dresden to Vienna (University of Natural Resources and Applied Life Sciences) to Berlin (Federal Institute for Material Research and Testing) and then finally to Ghent, the conference has constantly evolved towards a truly international level. This can be seen by the language used. The first two conferences were entirely in the German language. During the conference in Berlin however, the change from the German to English language was especially apparent as some presentations were conducted in German and others in English. Now in Ghent all papers will be presented in English. Participants now, not only come from Europe, but also from other continents. Although the conference will move back to Germany again next year (2008) in Darmstadt, the international concept will remain, since so much work in the field of probabilistic safety evaluations is carried out internationally. In two years (2009) the conference will move to Delft, The Netherlands and probably in 2010 the conference will be held in Szczecin, Poland. Coming back to the present: the editors wish all participants a successful conference in Ghent

MH-60 Seahawk / MQ-8 Fire Scout interoperability

Approved for public release; distribution is unlimitedAs part of a Naval Postgraduate School's capstone project in Systems Engineering, a project team from Cohort 311-0911 performed a Systems Engineering analysis. This Project focused on defining alternatives for enhanced Anti-Surface Warfare (ASUW) mission effectiveness through increased interoperability and integration for the Fire Scout Unmanned Air Vehicle and Seahawk helicopter. Specifically, the Project explored the available trade space for enhancing communications back to the ship for analysis and decision-making. Modeling and Simulation (MandS) was used to assess the impact of enhanced communication on specific Key performance Parameters (KPPs) and Measures of Effectiveness (MOEs) associated with the ASUW mission. Once the trade space was defined, alternatives were analyzed and a recommendation provided that supports near-, mid-, and long-term mission enhancement