An integrated reliability-based design optimization of offshore towers

Karadeniz, H.; Toğan, Vedat; Vrouwenvelder, Ton

doi:10.1016/j.ress.2009.02.008

Cited by 35 publications

(15 citation statements)

References 16 publications

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“…Karadeniz et al (2009) optimized offshore towers using SQP and FORM. A filter-based SQP algorithm to solve RBDO problems with highly nonlinear constraints was proposed by Hsu and Chan (2010).…”

Section: Pr[h(y ) < 0] ≈ (−β Hl )mentioning

confidence: 99%

Reliability-based design optimization using SORM and SQP

Strömberg

2017

Struct Multidisc Optim

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In this work a second order approach for reliabilitybased design optimization (RBDO) with mixtures of uncorrelated non-Gaussian variables is derived by applying second order reliability methods (SORM) and sequential quadratic programming (SQP). The derivation is performed by introducing intermediate variables defined by the incremental iso-probabilistic transformation at the most probable point (MPP). By using these variables in the Taylor expansions of the constraints, a corresponding general first order reliability method (FORM) based quadratic programming (QP) problem is formulated and solved in the standard normal space. The MPP is found in the physical space in the metric of Hasofer-Lind by using a Newton algorithm, where the efficiency of the Newton method is obtained by introducing an inexact Jacobian and a line-search of Armijo type. The FORM-based SQP approach is then corrected by applying four SORM approaches: Breitung, Hohenbichler, Tvedt and a recent suggested formula. The proposed SORMbased SQP approach for RBDO is accurate, efficient and robust. This is demonstrated by solving several established benchmarks, with values on the target of reliability that are considerable higher than what is commonly used, for mixtures of five different distributions (normal, lognormal, Gumbel, gamma and Weibull). Established benchmarks are also generalized in order to study problems with large number of variables and several constraints. shown that the proposed approach efficiently solves a problem with 300 variables and 240 constraints within less than 20 CPU minutes on a laptop. Finally, a most well-know deterministic benchmark of a welded beam is treated as a RBDO problem using the proposed SORM-based SQP approach.

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Section: Pr[h(y ) < 0] ≈ (−β Hl )mentioning

confidence: 99%

Reliability-based design optimization using SORM and SQP

Strömberg

2017

Struct Multidisc Optim

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“…Different tower heights were analyzed to obtain the best formulation in terms of cost. An integrated reliabilitybased design optimization of offshore towers was presented by Karadeniz et al [2009]. As a demonstration, they optimized a tripod tower subject to reliability constraints based on limit states of the critical stress, buckling and the natural frequency.…”

Section: Tower Design Studiesmentioning

confidence: 99%

Multidisciplinary design optimization of offshore wind turbines for minimum levelized cost of energy

et al. 2014

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This paper presents a method for multidisciplinary design optimization of offshore wind turbines at system level. The formulation and implementation that enable the integrated aerodynamic and structural design of the rotor and tower simultaneously are detailed. The objective function to be minimized is the levelized cost of energy. The model includes various design constraints: stresses, deflections, modal frequencies and fatigue limits along different stations of the blade and tower. The rotor design variables are: chord and twist distribution, blade length, rated rotational speed and structural thicknesses along the span. The tower design variables are: tower thickness and diameter distribution, as well as the tower height. For the other wind turbine components, a representative mass model is used to include their dynamic interactions in the system. To calculate the system costs, representative cost models of a wind turbine located in an offshore wind farm are used. To show the potential of the method and to verify its usefulness, the 5 MW NREL wind turbine is used as a case study. The result of the design optimization process shows 2.3% decrease in the levelized cost of energy for a representative Dutch site, while satisfying all the design constraints.

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“…Previous studies show the advantages of the integrated design with either limited design constraints or disciplines [4,5,6,7,8,9,10,11]. The work presented herein addresses some of the shortcomings of the previous works by developing an integrated design method with all the relevant disciplines (structure, aerodynamics, hydrodynamics and soil mechanics) and design constraints (buckling, fatigue damage and natural frequency) involved.…”

Section: Introductionmentioning

confidence: 99%