Optimization of Structures Under Stochastic Loads

by S. H. Kim, Korea Inst of Construction, Technology, Seoul, Republic of Korea,
Y. K. Wen, Korea Inst of Construction, Technology, Seoul, Republic of Korea,

Document Type: Proceeding Paper

Part of: Structural Safety and Reliability


A method for design under multiple stochastic loads based on optimization is developed. The objective function such as cost is minimized under the constraint that the probabilities of various limit states being reached are within allowable limits. The loads are treated as random processes and their combined effects evaluated by the load coincidence method. The limit states considered are either yielding or first plastic hinge at the member level or plastic collapse at the system level. A penalty function approach and a Sequential Unconstrained Minimization method are used. To expedite the analysis, a LRFD format is developed and used. The dependence of the resultant optimal design on the constraints used, e.g. at the member or system level is investigated. The proposed approach to the problem is shown to be a viable method and the design using a bi-level (member and system) reliability constraints is shown to yield more risk consistent results.

Subject Headings: Load and resistance factor design | Stochastic processes | Load factors | Plastic hinges | System reliability | Structural reliability | Computer programming | Load combinations

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