Integrated Reliability-Based Optimal Design of Structures

John Dalsgaard Sørensen, Palle Thoft-Christensen

Publikation: Bidrag til bog/antologi/rapport/konference proceedingKonferenceartikel i proceedingForskningpeer review

Resumé

In conventional optimal design of structural systems the weight or the initial cost of the structure is usually used as objective function. Further, the constraints require that the stresses and/or strains at some critical points have to be less than some given values. Finally, all variables and parameters are assumed to be deterministic quantities. In this paper a probabilistic formulation is used. Some of the quantities specifying the load and the strength of the structure are modelled as random variables, and the constraints specify that the reliability of the structure has to exceed some given value. The reliability can be measured from an element and/or a systems point of view. A number of methods to solve reliability-based optimization problems has been suggested, see e.g. Frangopol [I]. Murotsu et al. (2], Thoft-Christensen & Sørensen (3] and Sørensen (4).
For structures where the reliability decreases with time it is often necessary to design an inspection and repair programme. For example the reliability of offshore steel structures decreases with time due to corrosion and development of fatigue cracks. Until now most inspection and repair strategies are based on experience rather than on rational investigations, see e.g. Jubb [5] and Dunn [6]. As a result it can be expected that inspection and repair of the structure on the above-mentioned bases are not only uneconomic, but perhaps also unsatisfactory from a safety point of view.
In chapter 2 of this paper reliability-based optimal design is discussed. Next, an optimal inspection and repair strategy for existing structural systems is presented. An optimization problem is formulated , where the objective is to minimize the expected total future cost of inspection and repair subject to the constraint that the reliability at any time is acceptable (see Thoft-Christensen & Sørensen (7]). The reliability is estimated using first-order reliability methods, Thoft-Christensen & Murotsu (8] and Madsen et al. (9]. Finally, integration of the optimal inspection/repair strategy and the reliability-based optimal design problem is considered. A practically usable procedure to solve the described integrated optimization problem is presented and demonstrated on an offshore structure.
OriginalsprogEngelsk
TitelReliability and Optimization of Structural Systems : Proceedings of the 1st IFIP WG7.5 working conference on reliability and optimization of structural systems
RedaktørerP. Thoft-Christensen
Antal sider14
ForlagSpringer
Publikationsdato1987
Sider385-398
ISBN (Trykt)3-540-18570-4
StatusUdgivet - 1987
BegivenhedIFIP WG7.5 Working Conference on Reliability and Optimization of Structural Systems - Aalborg, Danmark
Varighed: 6 maj 19878 maj 1987
Konferencens nummer: 1

Konference

KonferenceIFIP WG7.5 Working Conference on Reliability and Optimization of Structural Systems
Nummer1
LandDanmark
ByAalborg
Periode06/05/198708/05/1987
NavnLecture Notes in Engineering
Vol/bind33
ISSN0176-5035

Fingerprint

Repair
Inspection
Optimal design
Offshore structures
Steel structures
Random variables
Costs
Corrosion

Emneord

  • Reliability-Based
  • Optimal Design
  • Structural Systems

Citer dette

Sørensen, J. D., & Thoft-Christensen, P. (1987). Integrated Reliability-Based Optimal Design of Structures. I P. Thoft-Christensen (red.), Reliability and Optimization of Structural Systems: Proceedings of the 1st IFIP WG7.5 working conference on reliability and optimization of structural systems (s. 385-398). Springer. Lecture Notes in Engineering, Bind. 33
Sørensen, John Dalsgaard ; Thoft-Christensen, Palle. / Integrated Reliability-Based Optimal Design of Structures. Reliability and Optimization of Structural Systems: Proceedings of the 1st IFIP WG7.5 working conference on reliability and optimization of structural systems. red. / P. Thoft-Christensen. Springer, 1987. s. 385-398 (Lecture Notes in Engineering, Bind 33).
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title = "Integrated Reliability-Based Optimal Design of Structures",
abstract = "In conventional optimal design of structural systems the weight or the initial cost of the structure is usually used as objective function. Further, the constraints require that the stresses and/or strains at some critical points have to be less than some given values. Finally, all variables and parameters are assumed to be deterministic quantities. In this paper a probabilistic formulation is used. Some of the quantities specifying the load and the strength of the structure are modelled as random variables, and the constraints specify that the reliability of the structure has to exceed some given value. The reliability can be measured from an element and/or a systems point of view. A number of methods to solve reliability-based optimization problems has been suggested, see e.g. Frangopol [I]. Murotsu et al. (2], Thoft-Christensen & S{\o}rensen (3] and S{\o}rensen (4).For structures where the reliability decreases with time it is often necessary to design an inspection and repair programme. For example the reliability of offshore steel structures decreases with time due to corrosion and development of fatigue cracks. Until now most inspection and repair strategies are based on experience rather than on rational investigations, see e.g. Jubb [5] and Dunn [6]. As a result it can be expected that inspection and repair of the structure on the above-mentioned bases are not only uneconomic, but perhaps also unsatisfactory from a safety point of view. In chapter 2 of this paper reliability-based optimal design is discussed. Next, an optimal inspection and repair strategy for existing structural systems is presented. An optimization problem is formulated , where the objective is to minimize the expected total future cost of inspection and repair subject to the constraint that the reliability at any time is acceptable (see Thoft-Christensen & S{\o}rensen (7]). The reliability is estimated using first-order reliability methods, Thoft-Christensen & Murotsu (8] and Madsen et al. (9]. Finally, integration of the optimal inspection/repair strategy and the reliability-based optimal design problem is considered. A practically usable procedure to solve the described integrated optimization problem is presented and demonstrated on an offshore structure.",
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Sørensen, JD & Thoft-Christensen, P 1987, Integrated Reliability-Based Optimal Design of Structures. i P Thoft-Christensen (red.), Reliability and Optimization of Structural Systems: Proceedings of the 1st IFIP WG7.5 working conference on reliability and optimization of structural systems. Springer, Lecture Notes in Engineering, bind 33, s. 385-398, IFIP WG7.5 Working Conference on Reliability and Optimization of Structural Systems, Aalborg, Danmark, 06/05/1987.

Integrated Reliability-Based Optimal Design of Structures. / Sørensen, John Dalsgaard; Thoft-Christensen, Palle.

Reliability and Optimization of Structural Systems: Proceedings of the 1st IFIP WG7.5 working conference on reliability and optimization of structural systems. red. / P. Thoft-Christensen. Springer, 1987. s. 385-398 (Lecture Notes in Engineering, Bind 33).

Publikation: Bidrag til bog/antologi/rapport/konference proceedingKonferenceartikel i proceedingForskningpeer review

TY - GEN

T1 - Integrated Reliability-Based Optimal Design of Structures

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AU - Thoft-Christensen, Palle

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N2 - In conventional optimal design of structural systems the weight or the initial cost of the structure is usually used as objective function. Further, the constraints require that the stresses and/or strains at some critical points have to be less than some given values. Finally, all variables and parameters are assumed to be deterministic quantities. In this paper a probabilistic formulation is used. Some of the quantities specifying the load and the strength of the structure are modelled as random variables, and the constraints specify that the reliability of the structure has to exceed some given value. The reliability can be measured from an element and/or a systems point of view. A number of methods to solve reliability-based optimization problems has been suggested, see e.g. Frangopol [I]. Murotsu et al. (2], Thoft-Christensen & Sørensen (3] and Sørensen (4).For structures where the reliability decreases with time it is often necessary to design an inspection and repair programme. For example the reliability of offshore steel structures decreases with time due to corrosion and development of fatigue cracks. Until now most inspection and repair strategies are based on experience rather than on rational investigations, see e.g. Jubb [5] and Dunn [6]. As a result it can be expected that inspection and repair of the structure on the above-mentioned bases are not only uneconomic, but perhaps also unsatisfactory from a safety point of view. In chapter 2 of this paper reliability-based optimal design is discussed. Next, an optimal inspection and repair strategy for existing structural systems is presented. An optimization problem is formulated , where the objective is to minimize the expected total future cost of inspection and repair subject to the constraint that the reliability at any time is acceptable (see Thoft-Christensen & Sørensen (7]). The reliability is estimated using first-order reliability methods, Thoft-Christensen & Murotsu (8] and Madsen et al. (9]. Finally, integration of the optimal inspection/repair strategy and the reliability-based optimal design problem is considered. A practically usable procedure to solve the described integrated optimization problem is presented and demonstrated on an offshore structure.

AB - In conventional optimal design of structural systems the weight or the initial cost of the structure is usually used as objective function. Further, the constraints require that the stresses and/or strains at some critical points have to be less than some given values. Finally, all variables and parameters are assumed to be deterministic quantities. In this paper a probabilistic formulation is used. Some of the quantities specifying the load and the strength of the structure are modelled as random variables, and the constraints specify that the reliability of the structure has to exceed some given value. The reliability can be measured from an element and/or a systems point of view. A number of methods to solve reliability-based optimization problems has been suggested, see e.g. Frangopol [I]. Murotsu et al. (2], Thoft-Christensen & Sørensen (3] and Sørensen (4).For structures where the reliability decreases with time it is often necessary to design an inspection and repair programme. For example the reliability of offshore steel structures decreases with time due to corrosion and development of fatigue cracks. Until now most inspection and repair strategies are based on experience rather than on rational investigations, see e.g. Jubb [5] and Dunn [6]. As a result it can be expected that inspection and repair of the structure on the above-mentioned bases are not only uneconomic, but perhaps also unsatisfactory from a safety point of view. In chapter 2 of this paper reliability-based optimal design is discussed. Next, an optimal inspection and repair strategy for existing structural systems is presented. An optimization problem is formulated , where the objective is to minimize the expected total future cost of inspection and repair subject to the constraint that the reliability at any time is acceptable (see Thoft-Christensen & Sørensen (7]). The reliability is estimated using first-order reliability methods, Thoft-Christensen & Murotsu (8] and Madsen et al. (9]. Finally, integration of the optimal inspection/repair strategy and the reliability-based optimal design problem is considered. A practically usable procedure to solve the described integrated optimization problem is presented and demonstrated on an offshore structure.

KW - Reliability-Based

KW - Optimal Design

KW - Structural Systems

KW - Reliability-Based

KW - Optimal Design

KW - Structural Systems

M3 - Article in proceeding

SN - 3-540-18570-4

T3 - Lecture Notes in Engineering

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BT - Reliability and Optimization of Structural Systems

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Sørensen JD, Thoft-Christensen P. Integrated Reliability-Based Optimal Design of Structures. I Thoft-Christensen P, red., Reliability and Optimization of Structural Systems: Proceedings of the 1st IFIP WG7.5 working conference on reliability and optimization of structural systems. Springer. 1987. s. 385-398. (Lecture Notes in Engineering, Bind 33).