Journal of Infrastructure Systems

We present an adaptive optimization model to find joint inspection and maintenance policies for infrastructure facilities under performance model uncertainty. The objective in the formulation is to minimize the total expected social cost of managing facilities over a finite planning horizon. Recent optimization models account for the uncertainty in the selection of facility performance models through an adaptive control approach. In this paper, we relax the assumptions of fixed and error-free inspections. We present a parametric study to analyze the effect of initial performance model uncertainty and bias on the expected total cost of managing a facility. The main observation is that reducing the initial variance in model uncertainty may be more important than reducing the initial bias. Our study also shows that cost savings can result from relaxing the constraint of a fixed inspection schedule.

Ground displacements are of primary concern when replacing pipelines in close proximity to existing buried utilities and structures. The objective of this research is to simulate the cavity expansion within the soil caused by the pipe-bursting process and to study the displacements of the soil in the vicinity of the burst pipe and at the ground surface with a finite difference plane strain model for an elastic-plastic medium. Soil parameters such as the bulk modulus, shear modulus, elastic modulus, Poisson’s ratio, dilation angle, and friction angle are varied in the simulations to study the effects of these parameters on the soil displacements due to pipe bursting. The results indicated that the soil movement was concentrated in a wedge-shaped zone between the centerline of the old pipe and the soil surface. In dense sand, the outward and upward effects dominate the displacement pattern in shallow pipe bursting, with considerable dilation occurring in the soil above the burst pipe. Close to the old pipe within the ground, the magnitude of ground movement is higher and decreases toward the ground surface. A higher bulk modulus and higher elastic modulus both lead to higher ground displacements. The simulation results are compared with the actual displacements measured in a field test.

The new Enhanced Coagulation Rule requires that drinking water utilities improve the removal of natural organic matter from their water. One common method of doing so is to “enhance” the performance of existing coagulation processes by increasing the coagulant dose, changing the coagulant type, or lowering the coagulation pH. There is growing concern that these treatment changes might cause degradation of cement and metallic components of drinking water treatment plant infrastructure. In a survey of enhanced coagulation impacts at 275 water utilities, 24% have reportedly already seen at least some infrastructure degradation. A comprehensive literature review highlights the potential causes for the degradation observed by utilities, and recommendations are provided to guide utilities seeking to minimize degradation and repair existing damage.

This paper quantifies the significant environmental aspects of a new high-end office building over 50 years of service life. A comprehensive environmental life-cycle assessment—including data quality assessment—was conducted to provide detailed information for establishing the causal connection between the different life-cycle elements and potential environmental impacts. The results show that most of the impacts are associated with electricity use and building materials manufacturing—in particular, electricity used in lighting, HVAC systems, and outlets; heat conduction through the structures; manufacturing and maintenance of steel; manufacturing of concrete and paint; water use and wastewater generation; and office waste management. Construction and demolition were found to have relatively insignificant impacts. The identified most significant aspects are quite predominant; 7% of all counted aspects cover over 50% of the life-cycle impacts. Practical applications of the study’s results could be in the environmentally conscious design and management of office buildings.

Allocation of funds for multidistrict highway agencies has traditionally been decided by the central administration based on predetermined criteria or formulas along with some consultation with regional agencies. In many cases, the consultation process with regional agencies is limited and ineffective. Such consultations are important because different regions tend to have different priorities, and the state of development and situations of their respective road networks are likely different. Applying a common formula and basis for funds allocation may not achieve the best results for all the regions and the entire network as a whole. This paper employs the genetic-algorithm (GA) optimization technique to allocate the total funds available to the district or regional agencies in order to best achieve specified central and regional agencies’ goals subject to operational and resource constraints. The fund allocation problem considers the overall objective of the central agency together with a goal specified by each district or regional agency. The practicality of the solution procedure is demonstrated with a simple pavement maintenance fund allocation problem of a three-region management structure administered by a central highway agency, and with different goals or objectives specified by the central and regional authorities. The performance of the proposed procedure, in terms of network pavement conditions, is compared to that of typical funds allocation approaches. The proposed two-stage GA procedure is shown to outperform typical traditional allocation systems.