Multi-objective probabilistic optimum monitoring planning considering fatigue damage detection, maintenance, reliability, service life and cost

Kim, Sunyong,Frangopol, Dan M. Springer-Verlag 2018 Structural and multidisciplinary optimization Vol.57 No.1

<P>Effective and efficient service life management is essential for a deteriorating structure to ensure its structural safety and extend its service life. The difficulties encountered in the service life management are due to the uncertainties associated with detecting and identifying structural damages, and assessing and predicting the structural performance. To reduce these uncertainties, continuous long-term structural health monitoring (SHM) can be employed. However, a rational and practical SHM planning is required to simultaneously maximize the accuracy, efficiency, and cost-effectiveness in service life management. This paper proposes a probabilistic optimum SHM planning based on five objectives to be simultaneously optimized: minimizing the expected damage detection delay, minimizing the expected maintenance delay, maximizing the damage detection time-based reliability index, maximizing the expected service life extension, and minimizing the expected life-cycle cost. The formulations of the five objectives are based on the probabilistic fatigue damage assessment. The monitoring plannings associated with both a single- and a multi-objective probabilistic optimization process (MOPOP) are investigated. For efficient decision making in identifying the essential objectives and selecting a well-balanced solution among the Pareto optimal solutions, the degree of conflict among objectives and objective weights are estimated. The novel approach proposed in this paper accounts for the interdependencies among the five objectives considered and demonstrates the role of the optimum SHM planning in service life management of deteriorating structures. The proposed MOPOP SHM planning is applied to the hull structure of a ship subjected to fatigue.</P>

Decision making for probabilistic fatigue inspection planning based on multi-objective optimization

Kim, Sunyong,Frangopol, Dan M. Elsevier 2018 International journal of fatigue Vol.111 No.-

<P><B>Abstract</B></P> <P>Probabilistic service life management of a deteriorating structure subjected to fatigue is a systemic process of assessing and predicting its structural performance, and establishing the optimum inspection and repair plans under uncertainty. In order to consider multiple objectives for optimum inspection and repair planning simultaneously, it is necessary to apply the multi-objective probabilistic optimization process (MOPOP) approach. In general, an increase in the number of objectives that requires probabilistic simulations for fatigue initiation and propagation results in high computational cost and difficulty in the visualization of Pareto optimal solutions and decision making to select the best solutions. Consequently, efficient decision making for multi-objective inspection planning of fatigue-sensitive structures is necessary. This paper deals with such a decision making framework for probabilistic fatigue inspection planning based on multi-objective optimization. The multiple objectives are converted into a single objective by using weights of the objectives, and as a result, a single optimum solution for inspection planning is obtained. The final decision making is performed by identifying the essential objectives and selecting the best Pareto optimal solution. Furthermore, the computational efficiency of the decision making and the effect of the uncertainties associated with fatigue crack initiation and propagation on the decision making for optimum inspection planning are investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Decision making framework to deal with a large number of objectives efficiently is presented for optimum inspection planning. </LI> <LI> Computational efficiency of the decision making is investigated. </LI> <LI> Effects of uncertainties associated with fatigue crack damage prediction on decision making are investigated. </LI> <LI> The proposed framework is illustrated through the optimum inspection planning for a fatigue-sensitive detail of an existing bridge. </LI> </UL> </P>

Simulating the construction process of steel-concrete composite bridges

Jie Wu,Dan M. Frangopol,Mohamed Soliman 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.5

This paper presents a master-slave constraint method, which may substitute the conventional transformed-section method, to account for the changes in cross-sectional properties of composite members during construction and to investigate the time-dependent performance of steel-concrete composite bridges. The time-dependent effects caused by creep and shrinkage of concrete are considered by combining the age-adjusted effective modulus method and finite element analysis. An efficient computational tool which runs in AutoCAD environment is developed to simulate the construction process of steel-concrete composite bridges. The major highlight of the developed tool consists in a very convenient and user-friendly interface integrated in AutoCAD environment. The accuracy of the proposed method is verified by comparing its results with those provided by using the transformed-section method. Furthermore, the computational efficiency of the developed tool is demonstrated by applying it to a steel-concrete composite bridge.

Using System Reliability to Evaluate and Maintain Structural Systems

Estes, Allen C.,Frangopol, Dan M. Computational Structural Engineering Institute of 2001 Computational structural engineering Vol.1 No.1

A reliability approach to evaluate structural performance has gained increased acceptability and usage over the past two decades. Most reliability analyses are based on the reliability of an individual component without examining the entire structural system. These analyses often result in either unnecessary repairs or unsafe structures. This study uses examples of series, parallel, and series-parallel models of structural systems to illustrate how the component reliabilities affect the reliability of the entire system. The component-system reliability interaction can be used to develop optimum lifetime inspection and repair strategies for structural systems. These examples demonstrate that such strategies must be based on the reliability of the entire structural system. They also demonstrate that the location of an individual component in the system has a profound effect on the acceptable reliability of that component. Furthermore, when a structure is deteriorating over time, the reliability importance of various components is a1so changing with time. For this reason, the most critical component in the early life of the structure may not tie the most critical later.

Influence line- model correction approach for the assessment of engineering structures using novel monitoring techniques

Strauss, Alfred,Wendner, Roman,Frangopol, Dan M.,Bergmeister, Konrad Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.9 No.1

In bridge engineering, maintenance strategies and thus budgetary demands are highly influenced by construction type and quality of design. Nowadays bridge owners and planners tend to include life-cycle cost analyses in their decision processes regarding the overall design trying to optimize structural reliability and durability within financial constraints. Smart permanent and short term monitoring can reduce the associated risk of new design concepts by observing the performance of structural components during prescribed time periods. The objectives of this paper are the discussion and analysis of influence line or influence field approaches in terms of (a) an efficient incorporation of monitoring information in the structural performance assessment, (b) an efficient characterization of performance indicators for the assessment of structures, (c) the ability of optimizing the positions of sensors of a monitoring system, and (d) the ability of checking the robustness of the monitoring systems applied to a structure. The proposed influence line- model correction approach has been applied to an integrative monitoring system that has been installed for the performance assessment of an existing three-span jointless bridge.

RELSYS: A computer program for structural system reliability

Estes, Allen C.,Frangopol, Dan M. Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.8

Most reliability-based analyses focus on the reliability of the individual components of a structure. There are many advantages to examining the components in combination as an entire structural system. This paper illustrates an algorithm used in the computer program RELSYS (RELiability of SYStems) which computes the system reliability of any structure which can be modeled as a series-parallel combination of its components. A first-order method is used to initially compute the reliability of each individual component. The system reliability is computed by successively reducing the series and parallel systems until the system has been simplified to a single equivalent component. Equivalent alpha vectors are used to account for the correlation between failure modes during the system reduction process.

RELTSYS: A computer program for life prediction of deteriorating systems

Enright, Michael P.,Frangopol, Dan M. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.9 No.6

As time-variant reliability approaches become increasingly used for service life prediction of the aging infrastructure, the demand for computer solution methods continues to increase. Effcient computer techniques have become well established for the reliability analysis of structural systems. Thus far, however, this is largely limited to time-invariant reliability problems. Therefore, the requirements for time-variant reliability prediction of deteriorating structural systems under time-variant loads have remained incomplete. This study presents a computer program for $\underline{REL}$iability of $\underline{T}$ime-Variant $\underline{SYS}$tems, RELTSYS. This program uses a combined technique of adaptive importance sampling, numerical integration, and fault tree analysis to compute time-variant reliabilities of individual components and systems. Time-invariant quantities are generated using Monte Carlo simulation, whereas time-variant quantities are evaluated using numerical integration. Load distribution and post-failure redistribution are considered using fault tree analysis. The strengths and limitations of RELTSYS are presented via a numerical example.

Influence line- model correction approach for the assessment of engineering structures using novel monitoring techniques

Alfred Strauss,Roman Wendner,Dan M. Frangopol,Konrad Bergmeister 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.9 No.1

In bridge engineering, maintenance strategies and thus budgetary demands are highly influenced by construction type and quality of design. Nowadays bridge owners and planners tend to include life-cycle cost analyses in their decision processes regarding the overall design trying to optimize structural reliability and durability within financial constraints. Smart permanent and short term monitoring can reduce the associated risk of new design concepts by observing the performance of structural components during prescribed time periods. The objectives of this paper are the discussion and analysis of influence line or influence field approaches in terms of (a) an efficient incorporation of monitoring information in the structural performance assessment, (b) an efficient characterization of performance indicators for the assessment of structures, (c) the ability of optimizing the positions of sensors of a monitoring system, and (d) the ability of checking the robustness of the monitoring systems applied to a structure. The proposed influence line- model correction approach has been applied to an integrative monitoring system that has been installed for the performance assessment of an existing three-span jointless bridge.