Life Cycle Management Of Structures Research Articles

Decision‐making for the efficient life cycle management of structures

AbstractStructures made of structural concrete are designed to withstand different time‐dependent or time‐independent influences during their expected service lifetime. Most of these influences can be considered in a sufficient manner by mathematical and statistical approaches, while some do appear combined with certain structural, environmental, and material boundary conditions. These can, in most cases, not be foreseen, verified or they change during the lifecycle of a concrete structure. It is therefore obligatory to rely on an efficient conservation strategy for each structure to ensure its safety and overall economic efficiency. For this purpose, the fib Model Code for Concrete Structures 2010 already suggests a general workflow to follow a predefined or provisional conservation strategy and condition control procedure. These existing proposals are yet of very general nature and disclaim practical decision‐making rules to survey and assess existing structures as part of a condition‐based conservation strategy. In this contribution, the main decision‐making options at an early stage of a construction's life cycle management are pointed out, considering their importance for a structure's time‐dependent performance and their relation to continuative decisions for conservation management. Proposals for the implementation of practical advice for condition‐based conservation strategies in international guidelines are made.

Automated finite element updating using strain data for the lifetime reliability assessment of bridges

The importance of improving the understanding of the performance of structures over their lifetime under uncertainty with information obtained from structural health monitoring (SHM) has been widely recognized. However, frameworks that efficiently integrate monitoring data into the life-cycle management of structures are yet to be developed. The objective of this paper is to propose and illustrate an approach for updating the lifetime reliability of aging bridges using monitored strain data obtained from crawl tests. It is proposed to use automated finite element model updating techniques as a tool for updating the resistance parameters of the structure. In this paper, the results from crawl tests are used to update the finite element model and, in turn, update the lifetime reliability. The original and updated lifetime reliabilities are computed using advanced computational tools. The approach is illustrated on an existing bridge.

Advanced damage tolerance and risk analysis methodologies and tools for aircraft structures containing multiple-site and multiple-element fatigue damages

This article presents the results obtained from the development of advanced damage tolerance analysis (DTA) and risk analysis methodologies and tools for aircraft structures, including build-up structures containing multiple-site fatigue damage (MSD) and multiple-element damage, to support the Canadian Forces aircraft structural life cycle management. The DTA methods developed include new closed-form solutions and generic finite element (FE) based tools to calculate the stress intensity factors and the β-solutions for build-up structural configurations. To facilitate the risk assessment, an in-house crack growth analysis program, CanGROW, was developed to simultaneously grow multiple cracks. Guidelines were established to calculate the residual strength of structures with MSD and multiple-element damage using global and/or local FE models, considering load redistribution among adjacent components. For the MSD risk analysis, an efficient Monte Carlo simulation technique was developed to determine the crack size distributions at different inspection intervals, which were then used in National Research Council Canada’s risk analysis code probabilistic damage tolerance analysis to calculate the single flight hour probability of failure. Case studies on critical locations of the CC-130 centre wing structure are presented to demonstrate the capability of the developed methods and tools.

The influence of temporal uncertainty of deterioration on life-cycle management of structures

In the life-cycle management of infrastructure systems, the decisions regarding the time and frequency of inspection, maintenance and replacement are confounded by sampling and temporal uncertainties associated with deterioration of the structural resistance. To account for these uncertainties, probabilistic models of deterioration have been developed under two broad categories, namely the random variable model and the stochastic process model. This paper presents a conceptual exposition of these two models and highlights their profound implications on age-based and condition-based preventive maintenance policies. The stochastic gamma process model of deterioration proposed here is more versatile than the random rate model commonly used in structural reliability literature.

Bayesian Updating of Damage Size Probabilities for Aircraft Structural Life-Cycle Management

A statistical approach to estimating the probabilistic distribution of composite damage sizes using aircraft service inspection data has been investigated. Bayesian updating methods were implemented to revise baseline composite damage size distributions using damage size data from the Federal Aviation Administration's Service Difficulty Reporting System. Updating was performed on the Boeing 757 and 767 wing composite trailing-edge devices, elevators and rudders, with the results demonstrating that the assumed baseline damage size estimates are conservative in nearly all cases. Component failure probabilities were recalculated using the updated damage size distributions, and these results show an overall improvement in reliability for the damage mechanisms analyzed. The results of the analysis demonstrate that an inspection and maintenance program that reports damage characteristics can be used to monitor the reliability of damage tolerant structures on a quantitative statistical basis. Recommendations are also made for improving current inspection data reporting systems, which would enhance the ability to gather detailed information on the characteristics of each structural damage event.