Infrastructures, Volume 5, Issue 6 (June 2020) – 8 articles

Over the last few decades, the attention on the safety of existing reinforced concrete (RC) structures has significantly increased. RC bridges, in particular, are highly relevant for strategic importance. In the Italian context, several of these bridges were built around 1960, when engineering practice commonly ignored or underestimated the presence of seismic actions. Therefore, it is fundamental to quantify as accurately as possible their seismic safety level with state-of-the-art analysis techniques. In this paper, an efficient procedure based on the multi-modal pushover analysis approach is proposed for the risk evaluation of several bridges of the Italian highway network. This procedure, tailored for portfolio level assessment, takes into account the non-linear behavior and the complex dynamic response this type of structure with limited computational effort. Three fundamental aspects are defined for the structural modelling of bridges, i.e., materials’ constitutive law, finite element type and nonlinear hinge models. Flexural and shear nonlinearities of piers are included to account for ductile and brittle damage potential. The standardized procedure guarantees consistent comparisons among different bridges of the same network in the form of risk indexes. Full article

Obtaining pedestrian trajectories by a vision-based methodology is receiving increasing attention in the literature over recent decades. Within the field of study of human-induced vibrations on footbridges, practical challenges arise when collecting the trajectories of high-density crowds during measurement campaigns. A cheap and robust methodology tackling these issues is presented and applied on a case study consisting of a real-life footbridge occupied with many pedestrians. A static camera setup consisting of low-cost action cameras with limited installation height is used. In addition, a drone camera was employed to collect a limited amount of footage. Pedestrians are equipped with colored hats and detected using a straightforward color-segmenting approach. The measurements are subjected to both systematic and random measurement errors. The influence of the former is theoretically investigated and is found to be of limited importance. The effect of the latter is minimized using a Kalman filter and smoother. A thorough assessment of the accuracy results reveals that the remaining uncertainty is in the order of magnitude of 2 to 3 cm, which is largely sufficient for the envisaged purpose. Although the methodology is applied on a specific case study in the present work, the conclusions regarding the obtained accuracy and employability are generic since the measurement setup can be extended to a footbridge with virtually any length. Moreover, the empirically obtained results of the presented case study should find use in the calibration of pedestrian dynamic models that describe the flow of high-density crowds on footbridges and the further development of load models describing crowd-induced loading. Full article

To a certain degree, composite railway sleepers and bearers have been recently employed as a replacement for conventional timber sleepers. Importantly, attributed to the rise in traffic demand, structural health monitoring of track structural members is essential to improve the maintenance regime and reduce risks imposed by any structural damage. A potential modern technique for detecting damage in railway components by using energy waves is called acoustic emission (AE). This technique has been widely used for concrete structures in other engineering applications, but the application for composites is relatively limited. Recently, fiber-reinforced foamed urethane (FFU) composites have been utilized as railway sleepers and bearers for applications in the railway industry. Neither does a design standard exist, nor have the inspection and monitoring criteria been properly established. In this study, three-point bending tests were performed together with using the AE method to detect crack growth in FFU composite beams. The ultimate state behaviors are considered to obtain the failure modes. This paper is thus the world’s first to focus on damage detection approaches for FFU composite beams using AE technology, additionally identifying the load-deflection curves of the beams. According to the experimental results, it is apparent that the failure modes of FFU composite beams are likely to be in brittle modes. Through finite element method, the results were in good agreement with less than 0.14% discrepancy between the experimental and numerical data. The attractive insights into an alternative technique for damage assessment of the composite components will help railway engineers to establish structural monitoring guidelines for railway composite sleepers and bearers. Full article

This article presents the latest improvements in a recently developed nondestructive testing (NDT) approach for early detection of various flaws (corrosion, delamination, and concrete cracking) in reinforced concrete (RC) bridge decks. The proposed method involves the use of internal steel reinforcement as a wave guide for transmitting ultrasonic waves through the system and the measurement of leaked energy from the surface of the concrete. This paper builds upon the progress made in the previously published phases of the project and aims to further explore the capabilities and practicality of the proposed NDT method. Specifically, the limits of propagation distance, effect of bidirectional reinforcement, methods of attachment and coupling of the sensors to the reinforcement and concrete, and suggestions for optimal sensor arrays are discussed in this paper based on the findings from the most recent laboratory tests and pilot field tests. The results show that with careful placement of sensors and data interpretation, early stages of localized corrosion and delamination can be detected, even when bidirectional and multiple layers of reinforcement are present. For field applications, an angled seat made of fast-setting Hydrocal gypsum cement is recommended, and it is projected that the optimal angle of attachment is 33 degrees or less from the vertical axis. Full article

An environmental impact assessment (EIA) involves the evaluation of information about pipe raw materials, processes, and product manufacturing to obtain the associated emissions and ecological impacts. Open-cut (OC) pipeline replacement involves digging a trench along the length of the proposed pipeline, placing the pipe in the trench on suitable bedding materials, and then embedding and backfilling. The trenchless cured-in-place pipe (CIPP) method involves a liquid thermoset resin saturated material that is inserted into the existing pipeline by hydrostatic or air inversion or by mechanically pulling-in and inflating. The liner material is cured-in-place using hot water or steam or light cured using ultraviolet light, resulting in the CIPP product. The objectives of this paper are: (1) to present a literature review on the progress acquired over the years in understanding the environmental impacts from the OC and CIPP methods, (2) to analyze and compare the environmental impacts for small diameter sanitary sewers (SDSS) using USEPA’s tool for the reduction and assessment of chemical and other environmental impacts (TRACI) methodology from the SimaPro software, and (3) to identify the factors that influence the environment for the OC and CIPP methods. Published papers were identified that reported the environmental impacts from the OC and CIPP methods over a period from 1989 through to 2020. An actual case study based on the City of Pasadena, California, river basin was used to carry out an environmental analysis for small diameter OC and CIPP methods. The literature review suggests that the material production phase consumes a large amount of energy and is a major contributor of environmental impacts. Higher environmental impacts from the OC method are a result of longer project durations and more equipment requirements compared to the CIPP. The assessment results show that, on average, CIPP renewal caused 68% less environmental impact, 75% less impact on human health, and 62% less resource depletion as compared to the OC replacement for SDSS. The liner, felt, and resin influenced the environment the most for CIPP as compared to the OC method, where the power consumption of construction equipment and the pipe material had the greatest environmental impacts. It can be concluded that the comparison of the environmental impacts from pipeline renewal and replacement is an important element when considering a sustainable underground infrastructure development. The pipe material and outside diameter should be considered during the installation phase by OC and CIPP methods to allow a detailed evaluation and comparison of their sustainability impacts. This study can be further developed for analyzing the environmental impacts and associated costs of the OC and CIPP methods for sanitary sewers with different project and site conditions. Full article

The US Department of Transportation and Federal Highway Administration require routine inspections to monitor bridge deterioration. Typically, bridge inspections are conducted every 24 months. This timeframe was determined solely based on engineering judgment. The objective of this study is to develop probabilistic models to forecast bridge deterioration and statistically determine the optimal inspection intervals. A two-dimensional Markov process model that considers the current condition of a bridge, and number of years that the bridge has been in that condition, is created to predict future bridge conditions based on historical data. Using the forecasting model, a statistical process is developed to determine the optimal inspection intervals. The proposed methodology in this study is implemented, utilizing a dataset consisting of information about deterioration conditions of more than 17,500 bridges in the state of New York from 1992 to 2018. The outcomes of the statistical analysis indicate that the typical 24-month inspection interval is considerably pessimistic, and not necessary for all bridges currently in condition 5 or higher. However, the 24-month interval is too optimistic and risky for bridges currently in condition 4 or lower. The outcomes of this study help bridge owners and transportation agencies assign maintenance resources efficiently, and invest the millions of dollars currently allocated for unnecessary inspections in much-needed infrastructure development projects. Full article

Reinforced concrete retaining walls are concrete structures that are built to retain natural soil or fill earth. This study examines the lower cost-optimized design of retaining walls. Recently, a large number of modern optimization techniques were published, but a small number of them were proposed for reinforced concrete retaining walls. The proposed method develops a heuristic optimization approach to achieve the optimal design of these structures. This method simultaneously satisfies all structural, geotechnical, and European Code design restraints while decreasing the total cost of these structures. In order to confirm the efficiency and accuracy of the proposed method, characteristic retaining wall examples are demonstrated. Furthermore, the parametric investigation is examined to study the result of pertinent parameters on the minimum-cost static and seismic design of retaining structures. Full article

Quantity Surveying (QS) is a process concerned with controlling and managing the costs of construction projects. QS Measurement relies on sophisticated measurement rules that are understood by experienced practitioners. Traditional QS systems, such as standard paperwork, are time-consuming and only approximate the cost estimate. This paper aims to design and deploy a web-based framework for automating the cost estimation of concrete construction, using ASP.NET. It introduces a user-friendly interface, which ensures that the work is completed in the chronological order of the construction phases. The proposed QS framework offers a reliable and time-efficient estimation method, in comparison to other methods (i.e., human labor using paper or Excel), which was tested using real data and was validated by experts and consultant companies. Furthermore, it automated the reading of project information from construction maps, which reduced errors when estimating costs. It could also automatically determine the project location using Google Maps and could quickly guide the user to the location. The proposed QS framework automated the manual and Excel work of cost computing with an accuracy of 99%, reducing human calculation errors. It also effectively reduced the calculation time to only three days (compared to 114 days of manual work or 19 days of Excel work). The comparison result of the Quantity Surveyor’s average paid salary indicated that using web-based QS framework helps in reducing the cost estimation time and labor costs. Full article