Reliability-Based Optimization in Structural Engineering

A lifetime optimization methodology for planning the inspection and repair of structures that deteriorate over time is introduced and illustrated through numerical examples. The optimization is based on minimizing the expected total life-cycle cost while maintaining an allowable lifetime reliability for the structure. This method incorporates: (a) the quality of inspection techniques with different detection capabilities; (b) all repair possibilities based on an event tree; (c) the effects of aging, deterioration, and subsequent repair on structural reliability; and (d) the time value of money. The overall cost to be minimized includes the initial cost and the costs of preventive maintenance, inspection, repair, and failure. The methodology is illustrated using the reinforced concrete T-girders from a highway bridge. An optimum inspection/repair strategy is developed for these girders that are deteriorating due to corrosion in an aggressive environment. The effect of critical parameters such as rate of co...

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Life-cycle cost design of deteriorating structures

Summary In comparison with the well-researched field of analysis and design of structural systems, the lifecycle performance prediction of these systems under no maintenance as well as under various maintenance scenarios is far more complex, and is a rapidly emergent field in structural engineering. As structures become older and maintenance costs become higher, different agencies and administrations in charge of civil infrastructure systems are facing challenges related to the implementation of structure maintenance and management systems based on life-cycle cost considerations. This article reviews the research to date related to probabilistic models for maintaining and optimizing the lifecycle performance of deteriorating structures and formulates future directions in this field.

Probabilistic models for life-cycle performance of deteriorating structures: review and future

In comparison with the well-researched field of analysis and design of structural systems, the life-cycle performance prediction of these systems under no maintenance as well as under various maintenance scenarios is far more complex, and is a rapidly emergent field in structural engineering As structures become older and maintenance costs become higher, different agencies and administrations in charge of civil infrastructure systems are facing challenges related to the implementation of structure maintenance and management systems based on life-cycle cost considerations This article reviews the research to date related to probabilistic models for maintaining and optimizing the life-cycle performance of deteriorating structures and formulates future directions in this field

Probabilistic models for life‐cycle performance of deteriorating structures: review and future directions

Concrete structures may be affected by aging or changes in strength and stiffness beyond the baseline conditions assumed for design. These changes may impair the safety and serviceability of the structure, and should be considered as part of the process by which a structure is evaluated for continued future service. Methods are being developed using structural reliability principles to evaluate time-dependent reliability of reinforced or prestressed concrete structures. These methods enable the impact on safety and serviceability of uncertainties in loading conditions, structural strength, and strength degradation due to aggressive environmental stressors to be assessed qualitatively. Parametric analyses show that the reliability is sensitive to the choice of initial component strength and strength degradation models. Less sensitivity is found to correlate component strengths within a system. Identification of the critical components before performing system reliability analysis is important in reducing the size of the analysis. The role of periodic inspection and maintenance in enabling a target reliability level to be met over a period of continued service also is considered.

Reliability-Based Service-Life Assessment of Aging Concrete Structures

A new strategy for inspection and repair of structural elements and systems is presented. The total cost of inspection and repair is minimized with the constraints that the reliability of elements and/or of the structural system are acceptable. The design variables are the time intervals between inspections and the quality of the inspections. Numerical examples are presented to illustrate the performance of the strategy. The strategy can be used for any engineering system where inspection and repair are required.

J. D. S⊘rensen

Papers

Optimal strategy for inspection and repair of structural systems