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The subway is one of the most important public infrastructure systems able to accommodate huge numbers of passengers daily and across the world. Hence, governments are always obliged to provide and secure a large amount of funds to maintain the required levels of performance. Nevertheless, the majority of current operating subway networks have faced significant deterioration in their provided services. This deterioration is not just confined to the unavailability of sufficient funds from governments, but also to the absence of comprehensive maintenance plans and a lack of documentation of past maintenance. In the same manner, governments are facing problems securing sufficient funds to maintain the operational efficiency of subway networks. This research presents a model for the condition assessment and budget allocation optimization of subway operating systems. The model incorporates technical maintenance information and maintenance progress metrics for each subway component defined on a building information modeling (BIM) model. The output of this model is utilized by BIM as an interoperable platform to regulate maintenance action documentation and track the actual maintenance progress status in subways. The selected operating systems were identified based on their contribution to the level of service. These systems include overhead catenary, communications, rolling stock, railway tracks, ticketing, lighting & power supply rectifier stations, and centralized control. A BIM-based model was developed to integrate the optimized maintenance plans with the modeled subway components and to compare the actual maintenance practices with optimized planned actions. Cairo Metro line 1 was adopted as a case study to showcase the main characteristics of the developed model. The results of the developed model reveal proper workability represented by running the developed coding scripts that correctly reflect the segregated maintenance plans into schedules integrated with the developed BIM model. [ABSTRACT FROM AUTHOR]

Bridge networks are a pillar of any national economy, and regular maintenance should be a high priority. Many transportation agencies require the condition assessment of concrete bridge decks as part of maintenance programs. Conventional, nondestructive bridge deck inspection techniques include hammer sounding and chain dragging. Ground penetrating radar (GPR) has been extensively used in recent years and has become an invaluable technique due to its high level of accuracy, speed, and low cost. This study provides a method to locate the corroded areas of the bridge deck slab in addition to getting structural properties such as rebar diameter, number and spacing. A clear methodology for the data collection, processing, and analysis of collected raw data is presented. Data is collected on site using ground-coupled GPR and then numerical amplitude method is used in the analysis. The study also clearly shows how to determine (1) bridge deck slab thickness, (2) asphalt layer thickness, (3) arrangement of steel rebar of the slab, (4) plotting corrosion map, and (5) generation deterioration model. Gathered data are grouped into four clusters using three clustering techniques based on the RapidMiner platform. GPR data interpretation is performed using integration between the amplitude method and visual interpretation, with threshold calibration based on K-means clustering. Simultaneously, the generated corrosion map is validated using the Weibull-based deterioration curves adopted by the New York State Department of Transportation and used since 1981, and the condition ratings used by the Federal Highway Administration in the United States. The corrosion index calculated from the clustered data is so close to the condition index obtained by the deterioration curve. A finite-element analysis is conducted in parallel to compare the stresses on the slab deck with the developed corrosion map. A sensitivity analysis is performed to identify the formula governing the amplitudes with the rebar area based on the finite-element analysis and the validated corrosion map. [ABSTRACT FROM AUTHOR]

The manuscripts involve the performance of GPR in defect detection, novel data processing and interpretation techniques, deterioration and rehabilitation models, and GPR applications in the inspection, corrosion mapping, condition assessment, and asset management of concrete structures. This Special Issue includes a collection of papers that address the practical applications of GPR to various civil infrastructure systems. [Extracted from the article]

The deterioration of water pipelines leads to impaired water quality, increased breakage rate, and reduced hydraulic capacity. The planning of maintenance programs for water pipelines is essential to minimize health and safety concerns and ensure an adequate supply of water in a safe, cost-effective, reliable, and sustainable manner. It is essential to assess the performance of water pipelines to assist municipalities in planning inspection and rehabilitation programs for their pipelines. Several models have been developed to assess the condition or performance of water pipelines based on several affecting factors. However, none of them considered the interdependency relationships between the factors. Moreover, some models did not account for the factors' weights uncertainty. This paper presents the development of performance assessment models for water pipelines. The models consider three groups of factors affecting water pipeline performance, namely, physical, environmental, and operational. The models were developed using data collected from questionnaire surveys distributed among water pipeline experts in Qatar. The factors' weights were calculated using four different methods, namely, analytic hierarchy process (AHP), fuzzy AHP (FAHP), analytic network process (ANP), and fuzzy ANP (FANP). The results showed that the FANP is the most accurate method since it incorporates the interdependency and uncertainty into the decision making process. [ABSTRACT FROM AUTHOR]

Selecting the appropriate contractor is a significant step to highway project success. The process of selection is subjected to uncertainty and influence of criteria other than bid price. This paper presents an approach to prioritize competitive contractors at the prebidding stage for highway projects by utilizing the analytic network process (ANP) and Monte Carlo simulation. Both techniques are integrated on a single platform to build the proposed model. Initially, the main quantitative and qualitative criteria affecting the contractors' selection process are identified and studied. The effective criteria in the selection process were obtained from experts and literature. A structured questionnaire was designed and sent to experts in highway projects. The ANP was used to prioritize these criteria subsequently, and Monte Carlo simulation was utilized to develop the selection model. The applicability of the proposed model was tested using four real cases of highway projects. It was concluded that using the lowest bid price as a sole criterion for selecting the best contractors may not result in an optimum solution. [ABSTRACT FROM AUTHOR]

In this study, the applications and the limitations of the Ground-penetrating radar (GPR) investigation have been addressed with the main objective of improving the efficient GPR application of subsurface surveys on Korean expressways. The depth of investigation and detection performance of anomalous objects have been studied using two different types of multichannel GPR on the Korean Expressway Corporation's nondestructive testing testbed for subsurface detection. Based on the field survey, it was found that utilizing the plane view by depth, cross-sectional and longitudinal profile data of the multichannel GPR simultaneously, analysis and evaluation of the GPR signals are more efficient and practical. Although there was a difference in the frequency of use, the precision difference between two GPR is almost similar in the investigation depth and detection performance of the pavement subsurface anomaly. Under an asphalt concrete standard pavement section, the effective depth of cavity detection is 1–1.5 m, while detection under concrete pavement is less than 1.0 m. In addition, there is still a need to calibrate depths using field cores when constructing a 3D underground facility map. [ABSTRACT FROM AUTHOR]

This paper develops a life cycle assessment framework for embodied environmental impacts of building construction systems. The framework is intended to be used early in the design stage to assist decision making in identifying sources of higher embodied impacts and in selecting sustainable design alternatives. The framework covers commonly used building construction systems such as reinforced concrete construction (RCC), hot-rolled steel construction (HRS), and light steel construction (LSC). The system boundary is defined for the framework from cradle-to-grave plus recycling and reuse possibilities. Building Information Modeling (BIM) and life cycle assessment are integrated in the developed framework to evaluate life cycle embodied energy and embodied greenhouse emissions of design options. The life cycle inventory data used to develop the framework were extracted from BIM models for the building material quantities, verified Environmental Product Declarations (EPD) for the material production stage, and the design of construction operations for the construction and end-of-life stages. Application of the developed framework to a case study of a university building revealed the following results. The material production stage had the highest contribution to embodied impacts, reaching about 90%. Compared with the conventional RCC construction system, the HRS construction system had 41% more life cycle embodied energy, while the LSC construction system had 34% less life cycle embodied energy. When each system was credited with the net benefits resulting from possible recycling/reuse beyond building life, the HRS construction system had 10% less life cycle embodied energy, while the LSC construction system had 68% less life cycle embodied energy. Similarly, the HRS construction system had 29% less life cycle greenhouse gas (GHG) emissions, while the LSC construction system had 62% less life cycle GHG emissions. Sustainability assessment results showed that the RCC construction system received zero Leadership in Energy and Environmental Design (LEED) credit points, the HRS construction system received three LEED credit points, while the LSC construction system received five LEED credit points. [ABSTRACT FROM AUTHOR]

The objective of this paper is to apply the life cycle assessment methodology to assess the environmental impacts of light steel framed buildings fabricated from cold formed steel (CFS) sections. The assessment covers all phases over the life span of the building from material production, construction, use, and the end of building life, in addition to loads and benefits from reuse/recycling after building disposal. The life cycle inventory and environmental impact indicators are estimated using the Athena Impact Estimator for Buildings. The input data related to the building materials used are extracted from a building information model of the building while the operating energy in the use phase is calculated using an energy simulation software. The Athena Impact Estimator calculates the following mid-point environmental measures: global warming potential (GWP), acidification potential, human health potential, ozone depletion potential, smog potential, eutrophication potential, primary and non-renewable energy (PE) consumption, and fossil fuel consumption. The LCA assessment was applied to a case study of a university building. Results of the case study related to GWP and PE were as follows. The building foundations were responsible for 29% of the embodied GWP and 20% of the embodied PE, while the CFS skeleton was responsible for 30% of the embodied GWP and 49% of the embodied PE. The production stage was responsible for 90% of the embodied GWP and embodied PE. When benefits associated with recycling/reuse were included in the analysis according to Module D of EN 15978, the embodied GWP was reduced by 15.4% while the embodied PE was reduced by 6.22%. Compared with conventional construction systems, the CFS framing systems had much lower embodied GWP and PE. [ABSTRACT FROM AUTHOR]

The 2019 Canadian Infrastructure report card identified 60% of the subway system to be in a very poor to a poor condition. With multiple assets competing for the limited fund, new methodologies are required to prioritize assets for rehabilitation. The report suggested that adopting an Asset Management Plan would assist municipalities in maintaining and operating infrastructure effectively. ISO 55000 emphasized the importance of risk assessment in assessing the value of an organization's assets. Subway risk assessment models mainly focus on structural failures with minimum focus on functional failure impacts and network criticality attributes. This research presents two modules to measure the functional failure impacts of a subway network, given financial, social, and operational perspectives, in addition to the station criticality. The model uses the Fuzzy Analytical Network Process with application to Fuzzy Preference Programming to calculate the weights for seven failure impact attributers and seven criticality attributes. Data are collected using questionnaires and unstructured/structured interviews with municipality personnel. The analysis identified social impacts to have the highest score of 38%, followed by operational and financial impacts at 34% and 27.65%, respectively. The subway station criticality revealed station location to have the highest impact at 35%, followed by station nature of use and station characteristics at 30.5% and 31.82%, respectively. When integrated with probability of failure, this model provides a comprehensive risk index to optimize stations for rehabilitation. [ABSTRACT FROM AUTHOR]