Optimization of structures under reliability constraints. An illustrative example of a beam with random width and height
- Delft Univ. of Technology (Netherlands). Faulty of Aerospace Engineering
In a first step in the development of a program to optimize structures under reliability constraints, the example of a beam with random height and width is chosen. The height and width are modeled as correlated random fields, where only the heights at different points along the length of the beam are design variables. The design objective is the weight of the beam, and the design variables are the average values of the height. The constraint is now the probability of limit-state violation, in this case the probability of exceeding a predefined stress. For the reliability calculations a response surface method was chosen, because multiple limit states have to be evaluated quickly. Furthermore the response surface can be used to calculate the design sensitivities in an efficient manner. The measure used for probability of failure is the Hasofer-Lind reliability index {beta}, and the design sensitivities are the change in {beta} with respect to the design variables. It is shown that even a statically determinate beam which is optimized under reliability constraints has a different optimum than the equivalent deterministic design problem. In this case the stresses at the free end of the beam have a higher variability than at the clamped side. As a consequence the average height at the free end has to be increased. Furthermore the position of the optimum in the design space does not change even if the target reliability for the individual beam elements is increased.
- OSTI ID:
- 455468
- Report Number(s):
- CONF-9606279-; ISBN 0-7918-1491-2; TRN: IM9716%%317
- Resource Relation:
- Conference: 14. international conference on offshore mechanics arctic engineering (OMAE), Florence (Italy), 16-20 Jun 1996; Other Information: PBD: 1996; Related Information: Is Part Of Proceedings of the 15. international conference on offshore mechanics and arctic engineering -- OMAE 1996. Volume 2: Safety and reliability; Guedes Soares, C. [ed.] [Technical Univ. of Lisbon (Portugal)]; Bea, R.G. [ed.] [Univ. of California, Berkeley, CA (United States)]; Leira, B.J. [ed.] [SINTEF, Trondheim (Norway)]; Shetty, N.K. [ed.] [W.S. Atkins, Surrey (United Kingdom)]; Vinnem, J.E. [ed.] [Elf Petroleum Norge AS, Oslo (Norway)]; PB: 525 p.
- Country of Publication:
- United States
- Language:
- English
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