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DEPARTMENT OF
CIVIL ENGINEERING
You are cordially invited to a seminar organized by Centre for Offshore Research and Engineering, CORE and Department of Civil Engineering, NUS on
Stochastic Optimization and Design in view of Applications in Offshore Engineering
by
Professor Gerhart I. Schuëller Institute of Engineering Mechanics, University of Innsbruck, Austria, EU
And
Professor Héctor A. Jensen Department of Civil Engineering, Santa Maria University, Valparaíso, Chile
Date: Wednesday, 13 Oct 2010Time: 3.00 pm – 5.30 pm Break time 4.00 pm – 4.30 pm (refreshment)Venue: Engineering Auditorium, Faculty of
Engineering, National University of Singapore
Presentation 1
G. I. Schuëller Reliability‐based Optimization: An Overview and Applications in Lifetime‐oriented Design
Decision making constitutes an integral part in the design and construction of systems in engineering. In this way, it is possible to identify the best configuration of a system that fulfills prescribed performance criteria; in this case, best implies that the selected configuration is superior to others according to specific criteria, e.g. economical costs, etc. However, unavoidable uncertainties in the performance of a system may hinder the decision processes. For example, the scheduling of maintenance activities for fatigue‐prone metallic structures can be extremely involved, as damage accumulation is a highly uncertain process. A feasible means for taking decisions under uncertainty is the application of Reliability‐based Optimization (RBO). Such an approach allows selecting the best decision (with respect to a predefined criterion) while explicitly considering the effects of uncertainties.
Although RBO constitutes a powerful tool for design in engineering, its application in engineering practice has remained limited in the past as it is a numerically involved procedure. Therefore, several approaches have been developed in order render the RBO problem tractable. Thus, the objective of this contribution is presenting an overview on different approaches for solving challenging RBO problems. Besides discussing theoretical and practical aspects on these approaches, a critical appraisal on the applicability and limitations of each approach will be performed, in order to discern which approaches are most appropriate for a specific design problem. In addition to presenting an overview on different approaches for solving RBO problem, this contribution discusses the application of optimization tools for lifetime‐oriented design. This constitutes one of the most important applications of RBO, as the performance of a structural system during its lifetime is subject to inherent uncertainties. In particular, it is demonstrated how methods of RBO can be applied for scheduling maintenance activities of fatigue‐prone metallic components. This problem is of much relevance in a number of branches of engineering, such as aerospace engineering and particularly offshore engineering.
About the Speaker Professor Schuëller is Chair Professor at the Leopold‐Franzens University, Innsbruck, Austria, EU and director of its Institute of Engineering Mechanics since 1981. His field of research is stochastic methods in structural and engineering mechanics, specifically mathematical modeling of load and material properties, structural reliability, reliability of mechanical components, probabilistic fatigue, fracture and dynamic analysis and its application in space, aeronautical, wind, earthquake, ocean, nuclear and mechanical engineering.
He is author and co‐author of more than 400 papers published in various scientific journals and conference proceedings, editor and co‐editor of 3 books and author of a Monograph and a book on "Introduction to Structural Safety and Reliability".
Professor Schuëller is member of the editorial board of several prestigious journals. He has been invited as plenary keynote speaker to a number of international conferences and received several international awards. Additionally, Dr. Schuëller has also been a consultant to various major European corporations.
Presentation 2
H. A. Jensen Optimal Design and Tradeoff Analysis of Stochastic Dynamical Systems
In many practical applications response predictions are based on structural models whose parameters are uncertain. This is due to a lack of information about the value of system parameters external to the structure, such as environmental loads (earthquake, water wave and wind loadings) or internal such as material properties. Under uncertain conditions the field of robust reliability‐based optimization provides a realistic and rational framework for structural synthesis which explicitly account for the uncertainties. On the other hand, the analysis and design of many structural systems usually involves several design goals which are required to be maximized or minimized simultaneously. The design goals are potentially conflicting requirements reflecting technical and economical performances of a given system design. To accommodate these conflicting design goals, such as cost and reliability, and explore the design options the problem is formulated in terms of a multi‐objective optimization procedure. The results obtained from this formulation provide useful information to the designer for decision making and tradeoff analysis.
One of the difficulties for solving this type of problems is the high computational cost involved in the reliability analyses required during the optimization process. This is due to the fact that the reliability estimation of stochastic dynamical systems involves the estimation of failure probabilities in high‐dimensional uncertain parameter spaces. The corresponding optimization problems are solved by a gradient‐based optimization scheme. In particular an interior point algorithm is implemented here. The algorithm is combined with an efficient sensitivity analysis which is based on an advanced simulation technique. Example problems that consider non‐linear finite element building models under stochastic earthquake excitation and typical fixed jacket platforms subject to stochastic water wave loading are presented to illustrate the efficiency of the proposed approach. Numerical results indicate that the procedure is quite effective for analysis and design of complex structural systems.
About the Speaker Dr. Jensen is currently Professor in the Department of Civil Engineering at the Federico Santa Maria University in Chile. He is Mathematician Civil Engineer (University of Chile) and received his PhD in Applied Mechanics from the California Institute of Technology (CALTECH‐USA). Prof. Jensen has been Visiting Professor at several universities: University of California at Los Angeles (UCLA‐USA); California Institute of Technology (USA); University of Michigan (USA); University of Southern California (USA); and University of Innsbruck (Austria). At the same time he has been Visiting Researcher in a number of international universities and research institutions. His research interests are in the areas of random vibrations, reliability‐based design optimization, robust optimization, stochastic processes, finite elements, fuzzy optimization, and sensitivity and reliability analysis. Prof. Jensen has published numerous journal and conference papers in these areas.
Contact Person: Prof Andrew Palmer Tel: 6516 2994, Email: [email protected]
General Enquiry/Registration: Ms Norela Tel: 6516 4314, Email: [email protected]
***Seats are limited. Please register early. All are welcome and admission is free***
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