Optimal maintenance strategies for bridge networks using the supply and demand approach

This paper presents a probability-based approach for optimising the management of bridge networks. Most of the Bridge Management Systems are focused on condition features to ensure a minimum safety level for each individual bridge. Their location on the road network, the consequences of inadequate service due to maintenance actions are therefore not taken into consideration. These multiple criteria should be considered when scheduling maintenance activities. To overcome these limitations, a probabilistic supply and demand strategy is proposed for determining the optimal maintenance planning for each interconnected bridge. The problem is solved with genetic algorithms. One objective function is first introduced, corresponding to the summation of all the maintenance, failure, and user costs. Then, two conflicting objective functions are considered, the total user costs and the maintenance and rehabilitation costs. Safety and serviceability aspects are taken into account in the methodology and the theoretical and numerical developments are applied on a part of the French national network.     

Design and maintenance programme optimization for large infrastructure systems

The design, construction and operation of civil infrastructure systems in modern society has become a critical issue worldwide. These processes cannot be restricted to solving just the mechanical problem. On the contrary, they should be designed within a framework that considers their life cycle, taking into account all costs in which the owner (or operator) will incur during the lifetime of the structure, and the benefits derived from its existence. This paper presents a strategy for optimizing the maintenance of technical facilities based on their life cycle within which deterioration and sudden failure due to extreme events may occur. A renewal model for the sequence of structural failures is used to define the objective function. The proposed model is useful for defining both an optimal maintenance policy (number of interventions and the time between them) and the design parameters. It can also be used for investment, planning and operation of new and existing facilities. The results have shown that a rational programme for maintenance and structural updating is essential for defining the efficiency of the investment in infrastructure projects.     

Condition evaluation of suspension bridges for maintenance,repair and rehabilitation: a comprehensive framework

To indicate health status of bridges and help stakeholders make decision on maintenance, a comprehensive framework has been proposed to evaluate structural efficiency of suspension bridges using analytic hierarchy process. First, the analytical hierarchy model (i.e. hierarchical network together with data aggregation algorithms) has been constructed using multi-source data, including visual inspection, non-destructive testing and structural health monitoring information. Age-dependent variable weight theory is developed to account for the service history of elements ensuring the alignment of variation trend of index weights with the objective law in bridge maintenance and management activities. To overcome the limitations of factor-based variable weight model for weight adjustment, the factor- and age-based variable weight model has been adopted for data aggregation. Finally, four cases are used to test the effectiveness of the three models (i.e. constant weight model, factor-based variable weight model and factor- and age-based variable weight model). By comparing the performance of the three models, the recommended maintenance strategy derived from factor- and age-based variable weight model aligns more with the actual strategy than the other two. The factor- and age-based variable weight model outperforms both the factor-based variable weight model and constant weight model in helping bridge owners make maintenance decisions.     

Estimating the marginal cost of pavement damage by highway users on the basis of practical schedules for pavement maintenance,rehabilitation and reconstruction

Highway agencies worldwide strive to ensure that highway users pay fees that not only recover the costs of pavement damage but also are equitable. In addressing the limitations of past research and quantifying the resulting adverse consequences on their analysis outcomes, this paper presents a comprehensive framework to derive more representative estimates of pavement damage cost. The developed framework incorporates practical pavement repair schedules that include all the key repair categories as a basis for estimating the marginal pavement damage cost (MPDC). The framework was applied to pavements of different surface type, functional class and age. On average, the MPDC was found to range from $0.0032 per ESAL-mile on Interstate highways to $0.1124 per ESAL-mile on non-national highways. It was determined that in each highway functional class, the marginal cost of pavement damage is influenced significantly by the pavement material type, traffic levels and age. Within any specific functional class, it was determined that the marginal cost increases with increasing traffic level and pavement age. The study also determined that non-consideration of at least one key repair category such as reconstruction or routine maintenance leads to significant (27–45%) underestimation of the actual MPDC.     

Fit for the task: the future of the small scale domestic repair and maintenance industry in the UK

The poor condition of much of the UK's older housing stock is an important policy issue. Some disrepair arises because owners cannot afford work, because they are not aware of the need for it or because they do not know how to go about organizing it. However, the poor reputation of that sector of the building industry dealing with small scale domestic repair and maintenance is also a deterrent. If anything, the problems of this sector have worsened during the recession as the supply of unskilled ‘cowboy’ operators has increased. This paper reviews the factors leading to underinvestment and poor quality work in the privately owned housing stock and examines the extent to which the shortcomings of the building industry contribute to this phenomenon. It describes the results of a survey of firms operating in the domestic repair and maintenance sector of the UK building industry, the majority of which were very small. The survey examined the size and composition of firms, their organization and working practices, the types of work they carried out, how they went about obtaining business, the extent to which their work-force was trained and the problems they faced in competing with one another and with the cowboy sector. On the basis of the survey conclusions and discussions with a wide range of organisations representing the industry, consumers, local authorities and government, a series of options for reform are discussed with the aim of stimulating debate on the future of this sector of the construction industry. It is argued that the problems of the UK industry cannot be solved by tighter controls on builders alone, but by a range of measures designed to provide more support and training to reputable builders, measures to exert greater controls over building techniques and safety provision to reduce unfair competition and programmes to educate the consumer to demand better standards and to be willing to pay for them. Ultimately only compulsory measures may succeed in improving standards, but much could be achieved by voluntary licensing or registration schemes backed up by incentives to use qualifying firms such as guarantees. This is more likely to work if backed up for an initial period by government or local authority funding. In the long run, however, the improvements to building quality could save public money.     

Energy saving potential and strategies for electric lighting in future North European, low energy office buildings: A literature review

This article presents key energy use figures and explores the energy saving potential for electric lighting in office buildings based on a review of relevant literature, with special emphasis on a North European context. The review reveals that theoretical calculations, measurements in full-scale rooms and simulations with validated lighting programs indicate that an energy intensity of around 10 kWh/m² yr is a realistic target for office electric lighting in future low energy office buildings. This target would yield a significant reduction in energy intensity of at least 50% compared to the actual average electricity use for lighting (21 kWh/m² yr in Sweden). Strategies for reducing energy use for electric lighting are presented and discussed, which include: improvements in lamp, ballast and luminaire technology, use of task/ambient lighting, improvement in maintenance and utilization factor, reduction of maintained illuminance levels and total switch-on time, use of manual dimming and switch-off occupancy sensors. Strategies based on daylight harvesting are also presented and the relevant design aspects such as effects of window characteristics, properties of shading devices, reflectance of inner surfaces, ceiling and partition height are discussed.