Framework Convention on Climate Change

Cost-competent maintenance and management of civil infrastructure requires balanced consideration of both the structure performance and the total cost accrued over the entire life-cycle. Most existing maintenance and management systems are developed on the basis of life-cycle cost minimization only. The single maintenance and management solution thus obtained, however, does not necessarily result in satisfactory long-term structure performance. Another concern is that the structure performance is usually described by the visual inspection-based structure condition states. The actual structure safety level, however, has not been explicitly or adequately considered in determining maintenance management decisions. This paper reviews the recent development of life-cycle maintenance and management planning for deteriorating civil infrastructure with emphasis on bridges using optimization techniques and considering simultaneously multiple and often competing criteria in terms of condition, safety and life-cycle...

Maintenance and management of civil infrastructure based on condition, safety, optimization, and life-cycle cost∗

Our knowledge to model, analyse, design, maintain, monitor, manage, predict and optimise the life-cycle performance of structures and infrastructures under uncertainty is continually growing. However, in many countries, including the United States, the civil infrastructure is no longer within desired levels of performance and safety. Decisions regarding civil infrastructure systems should be supported by an integrated reliability-based life-cycle multi-objective optimisation framework by considering, among other factors, the likelihood of successful performance and the total expected cost accrued over the entire life-cycle. The primary objective of this paper is to highlight recent accomplishments in the life-cycle performance assessment, maintenance, monitoring, management and optimisation of structural systems under uncertainty. Challenges are also identified.

Life-cycle performance, management, and optimisation of structural systems under uncertainty: accomplishments and challenges 1

Plate slenderness limits for high strength steel sections

Bridge management systems have adopted Markov-chain models for predicting the future condition of bridge components, systems, and networks. These models are developed based on two assumptions. First, bridge inspections are performed at predetermined and fixed time intervals i.e., constant inspection period. Second, the future bridge condition depends only on the present condition and not on the past condition i.e., state independence. This paper evaluates the impact of these assumptions on the performance prediction of bridge deck systems using field data obtained from the Ministere des Transports du Quebec. Transition probability matrices are developed for the different elements of the deck system and adjusted for the variation in the inspection period using Bayes' rule. This investigation indicated that the variation in the inspection period may result in a 22% error in predicting the service life of a bridge deck system. Also, the statistical tests used to assess the validity of the state independence assumption of Markov chains showed that this assumption is acceptable with a 95% level of confidence, which is reasonable for network level analysis.

Performance Prediction of Bridge Deck Systems Using Markov Chains

The solution methods of multiobjective optimization have undergone constant development over the past three decades However, the methods available to date are not particularly robust Because of the complicated relationship between the rehabilitation cost and deterioration degree of infrastructure systems, it is difficult to find a near-optimal solution using common optimization methods Since genetic algorithms work with a population of points, they can capture a number of solutions simultaneously and easily incorporate the concept of Pareto optimality In this paper a simple genetic algorithm with two additional techniques, Pareto optimality ranking and fitness sharing, is implemented for the deck rehabilitation plan of network-level bridges, aiming to minimize the total rehabilitation cost and deterioration degree This approach is illustrated by a simple example and then applied to a practical bridge system with a large number of bridges

Multiobjective Optimization of Bridge Deck Rehabilitation Using a Genetic Algorithm

The pseudodynamic test is increasingly being used for testing structures under seismic loads. Due to the limited capacity of available equipment and also to economic reasons, testing is often required to be carried out on scaled models rather than full-scale structures. Although the similitude laws are well established, the selection of a suitable set of scale factors is often complicated due to the infinite number of possible sets. The various aspects to be considered in selecting a suitable set of scale factors are clarified. The question of possible differences in test results due to a difference in testing procedure is answered by means of tests on identical specimens using three typical procedures. It was found that the results obtained can be considered to be identical for practical purposes.

Pseudodynamic Testing of Scaled Models

Using CO2 emission quantities in bridge lifecycle analysis

Nominally identical 25 rolled beams for each group of three different lengths are tested carefully under a concentrated load applied vertically at the midspan of the compressive flange of span center. The variation of the geometrical and material imperfections are measured and the influences of the various parameters on the scattered test points of the lateral buckling are reviewed. The main parameter which highly influences the variation of the ultimate strength is the variable value of actual plastic moment. The obtained test results are also compared with the existing test data and design formulas. The coefficients of variation of the strength increase with beam length and these values are considerably low as compared with the past scattered data. Finally, a design formula is proposed to ensure empirically the lower bound for the scattered test values.

Strength Variation of Laterally Unsupported Beams

Statistical buckling experiments of 34 welded beams for each group of two different lengths are carried out under a concentrated load applied vertically at the midspan of the compressive flange of simply-supported beams. The influences of the variations of the various imperfection parameters on scattered test points of the lateral buckling are examined. The obtained test results are compared with the writers' previous test results of the rolled beams. The main imperfection parameter that highly influences the variation of the ultimate strength of the welded beams is the variable value of the actual full plastic moments, as already mentioned for the rolled beams. The welded beams, however, have a lower ultimate strength in the mean value and large coefficient of variation as compared with the rolled beams. The large variations in the compressive residual stresses and the initial lateral crookednesses in the welded beams may cause the large strength variation in the welded beams.

Yoshito Itoh

Papers

Multiobjective Optimization of Bridge Deck Rehabilitation Using a Genetic Algorithm

Pseudodynamic Testing of Scaled Models

Using CO2 emission quantities in bridge lifecycle analysis

Strength Variation of Laterally Unsupported Beams

Statistical Study of Experiments on Welded Beams