Journal of Infrastructure Systems

In response to the needs in waste management and environmental restoration during the last two decades, a new service sector has emerged in the United States and across the world. Civil engineers who serve this sector have taken the responsibilities to detect, locate, characterize, and speciate soils contaminated with a myriad of species, to predict their transport and fate in order to provide design/analysis methodologies and construction methods, for containment of hazardous waste, and restoration of the sites contaminated with such waste. The tasks undertaken include development of performance assessment techniques for the designed facilities, risk-assessment methods, and recycle/reuse of the waste material in other infrastructural needs. A brief review of the characteristics of the hazardous-waste sites in the United States is followed by an outline of the infrastructural needs in characterization, fate and transport analysis, containment of waste, and remediation of soil from a review of the emerging trends and developments. The need for synergism in solving the geoenvironmental issues and the requirement for sustainable improvement of the geoenvironment dictate cross-specialization and necessitates collaboration and communication between professionals across different disciplines of engineering and sciences.

A partially observable Markov decision process (MDP) model is presented that extends beyond completely observable approaches by recognizing that inspections do not yield perfect estimates of the true internal state of system components. The approach permits the exact solution of problems whose output is inspection and maintenance policies that prescribe when to inspect, how to inspect, when to repair and how to repair, so as to minimize discounted life-cycle costs. The extension to accommodate partial observability does, however, exact a significant computational demand. The model is demonstrated with a one-lane, two-girder bridge inspection, maintenance, and repair application.

This paper assesses deficiencies in highway bridges as a case study of the present state of an important segment of the nation's infrastructure. The National Bridge Inventory (NBI) contains a considerable amount of information about the characteristics of the U.S. highway bridge population. Condition ratings reflect physical deterioration due to environmental effects and traffic, and appraisal ratings indicate changes in traffic volume, existing load capacities, and compliance with safety standards related to bridge geometry and clearances. Expressed in percentages of bridge counts, the major deficiencies defined by low ratings rank as follows: deck geometry; structural evaluation; and conditions of substructure, superstructure and deck. Rank and percentages of deficiencies vary by superstructure material. Generally, structural deficiencies are lower for concrete bridges than for steel or timber bridges. Funding and maintenance policy differences among states and local governments are evident from the percentages of newly constructed or reconstructed bridges rated deficient and from the changes in the various deficiencies with age. The rates of increase with bridge age of the major deficiencies raise an interesting question: Are transportation growth and increase in vehicular loads more important than maintenance as causes of highway bridge deficiency or obsolescence?

Markovian transition probabilities have been used extensively in the field of infrastructure management to provide forecasts of facility conditions. However, existing approaches used to estimate these transition probabilities from inspection data are mostly ad hoc and suffer from important methodological limitations. In this paper, we present a rigorous econometric method for the estimation of infrastructure deterioration models and associated transition probabilities from condition rating data. This methodology, which is based on ordered probit techniques, explicitly treats facility deterioration as a latent variable, recognizes the discrete ordinal nature of condition ratings, and, as opposed to state-of-the-art methods, explicitly links deterioration to relevant explanatory variables. An empirical case study using a bridge inspection data set from Indiana demonstrates the capabilities of the proposed methodology.

Infrastructure-construction quality could be better assured by imposing more responsibility for quality process control on contractors, and by having owners place more effort on specifying clear inspection procedures and acceptance criteria. This type of specification, with better allocation of the responsibility between owners and contractors, is generally called quality-assurance (QA) specification. The purpose of this paper is to present results of research in developing a quality-acceptance method called Attribute–Double-Sampling Method (ADSM) for QA specifications. Application of ADSM for quality assurance on steel-bridge–painting construction is used to demonstrate the theory and application of the methodology, but the ADSM is generic and can be applied to a wide range of infrastructure-quality assessments. It enables the users to select sampling size and to control risk while accepting or rejecting the quality of a finished infrastructure product.

Nondestructive evaluation plays an important role in the assessment of the nation's infrastructure. The evaluation methods for reinforced and prestressed concrete facilities can become more reliable if the methods incorporate imaging technology, which has been implemented widely in many fields. Radiography, ground penetrating radar (in B-scan mode) and infrared thermography have established themselves in civil engineering practice. They are used to nondestructively locate steel reinforcement and concrete flaws, such as delaminations, cracks and honeycombing. This paper discusses the principles of these established methods, as well as their advantages and disadvantages. Radioactive computed tomography, microwave holography, microwave tomography and acoustic tomography are in various stages of development. This paper summarizes the basis for each new method and the results of recent research. It also discusses the potential advantages of the new methods and the barriers to their implementation in civil engineering applications. Examples of images obtained with each technology are provided.