Search

Oil and gas pipelines transport millions of dollars of products every day making the optimization of their long-term maintenance strategies an essential target for practitioners. Thus, this paper aims to optimize the maintenance plan of such pipelines by maximizing their lifetime average condition with the minimum possible cost. This is achieved in three steps: (1) developing a life-cycle cost model for such pipelines to determine their net present value (NPV) based on the different rehabilitation actions applied throughout their lifetime; (2) establishing a strategy to determine the condition index of such pipelines before and after any rehabilitation action applied throughout their lifetime; and (3) formulating the optimization model and applying the elitist non-dominated sorting genetic algorithm (NSGA-II) to determine the optimum maintenance plans for such pipelines. The optimization model is applied to a real-life case study to demonstrate its applicability. Key words: oil and gas pipelines, optimization, NSGA-II, life-cycle cost, condition index. Les oleoducs et gazoducs transportent des millions de dollars en produits chaque jour, faisant de sorte que l'optimisation des strategies d'entretien a long terme de ceux-ci soit une cible essentielle pour les praticiens. Ainsi, cette etude vise a optimiser le plan d'entretien de ces pipelines en maximisant leur etat moyen a vie au cout minimum possible. Cela se fait en trois etapes : (i) elaborer un modele de cout du cycle de vie pour ces pipelines afin de determiner leur valeur actualisee nette (VAN) en fonction des differentes mesures de rehabilitation appliquees tout au long de leur duree de vie; (ii) etablir une strategie pour determiner l'indice d'etat de ces pipelines avant et apres toute mesure de rehabilitation mise en oeuvre au cours de leur duree de vie; et (iii) formuler le modele d'optimisation et appliquer l'algorithme genetique NSGA-II (<< non-dominated sorting algorithm II >>) afin de determiner les plans d'entretien optimaux de ces pipelines. Le modele d'optimisation est utilise dans le cadre d'une etude de cas reelle pour demontrer son applicabilite. Mots-cles : oleoducs et gazoducs, optimisation, NSGA-II (<< non-dominated sorting algorithm II >>), cout du cycle de vie, indice d'etat., Introduction Pipelines are considered the safest and the most efficient way to transport oil and gas products (Kennedy 1993). However, their failure can cause significant social, environmental, and financial consequences. [...]

This experimental study evaluated the performance of modified asphalt mixtures prepared by incorporating 2%, 4%, and 6% linear low-density polyethylene (LLDPE) by weight of asphalt binder through a series of tests. The microstructural analyses using scanning electron microscopy (SEM) were conducted on asphalt samples to assess the engineering properties of the asphalt mixes. Finally, ANOVA statistical analysis has been employed to determine the statistical significance of the differences in all tests' means. Based on laboratory findings, the Marshall stability test result showed that the modified asphalt mixes up to 4% LLDPE had enhanced performance by 12.7% compared to the control mix. A significant decrease (up to 31.3%) in binder penetration was demonstrated due to the incorporation of LLDPE into the asphalt mix. The softening point of the LLDPE–asphalt mixes was increased by up to 17.6%. It was also demonstrated that the incorporation of such LLDPE dosages maintains the flow limits within the specified range; however, the flow of the asphalt mix with 4% LLDPE was 3.17 mm which is the nearest to the average value of the upper and lower acceptable limits. The air voids of mixes with LLDPE content more than 4% by was decreased to less than 4% which is not recommended in high-temperature climates to control mixture bleeding. Microscopic analysis revealed an improvement in the densification of asphalt microstructures, attributed to the LLDPE particles significantly changing the rheology and viscosity of the base mixture and making the hot asphalt mixture more homogeneous. Based on the physical and rheological properties investigated in this study, it could be concluded that 4% LLDPE produces the best performance in asphalt mixtures. Overall, the ANOVA analysis demonstrated that the incorporation of LLDPE into asphalt mixes has a significant impact on all of their properties. [ABSTRACT FROM AUTHOR]

This study underscores the potential of utilizing natural volcanic tuffs (NVTs) as supplementary cementitious materials (SCMs) in alignment with global sustainability efforts aimed at mitigating the cement industry's negative impacts on both the economy and the environment. Experimental investigations were conducted on concrete mixtures containing 10%, 20%, 30%, 40%, and 50% NVT as partial cement replacements to assess their influence on concrete's mechanical and microstructural properties. Based on the findings, concrete samples with 10% NVT replacements exhibited increased flexural and compressive strengths of 35.6% and 5.6%, respectively, compared with ordinary concrete after 28 days. The depth of water penetration in the concrete samples was significantly reduced by the inclusion of NVT, with a maximum reduction of 56.5%. Microstructural analysis using scanning electron microscopy (SEM) revealed enhanced densification of the concrete microstructures, attributed to the high pozzolanic activity of NVT use in cement-based composites. Analysis of variance (ANOVA) revealed statistically significant relationships between NVT content and both the compressive and flexural strengths of the concrete samples. In conclusion, substituting 10% cement with NVT not only enhances the mechanical properties of concrete but also decreases the energy demand for cement production and reduces carbon dioxide (CO2) emissions, thus contributing to more sustainable construction practices. [ABSTRACT FROM AUTHOR]

As urbanization increases, buildings require greater amounts of energy for heating and cooling, thereby necessitating the search for effective solutions. The courtyard is often considered a viable option; however, the limited availability and high cost of land resulting from rapid urbanization hinder its widespread use. Consequently, a courtyard with a cluster of buildings is proposed as a feasible solution to address land scarcity. Nonetheless, further investigation is required to effectively integrate this solution into neighborhood urban planning. This study examines the influence of three variables—courtyard orientation, courtyard size, and the arrangement of buildings around the courtyard—on the provision of cooling and heating for buildings. The research focuses on 216 experimental scenarios simulated using Revit software, which excels in its ability to accurately interpret input data and conduct real-time analysis depending on the variables of the building design. The results were recorded for the facades and ground, and the shaded area was computed for each scenario; following these measurements, the shadow areas on both the facade and ground were converted into percentages. The testing involved a group of buildings surrounding courtyards of four different shapes (square, rectangle, triangle, and circle). This approach aimed to identify the most efficient design for implementation in neighborhood planning contexts. The findings indicate that the shape of the courtyard significantly impacts cooling and heating of buildings. Specifically, the square courtyard is unsuitable for countries with Mediterranean climates, such as Jordan, as it can reduce shade coverage by 30%, leading to higher temperatures. Conversely, employing a rectangular courtyard results in a higher proportion of shadows compared to other shapes. The study further demonstrates the influence of the examined variables on the efficacy of the courtyard in cooling and heating of buildings. [ABSTRACT FROM AUTHOR]

In the absence of industry data, organisms, and researchers leverage free and available data, specifically building and demolition permits. Geospatial processing is essential to integrate information from various files into a single GIS layer containing all relevant attributes for analysis. This article proposes a Geographic Information System (GIS) processing model aimed at monitoring construction and demolition dynamics in the European metropolis of Lille to quantify the urban production of mineral waste from buildings. Author methodology is based on that that the deposit potential can be analyzed using the observation of the spatiotemporal dynamics of building and demolition permits. The results demonstrate that combining construction and demolition (C&D) permits with other GIS layers allows us to produce data to quantify demolition surfaces per year in a given French area. The applicability of this methodology extends to all French regions, providing insights into the impact of crises on deconstruction activities and C&D waste generation. The study focuses on C&D French public data bases (French government and European Metropolis of Lille) attributed to the region (area) of the European Metropolis of Lille (MEL) between 2013 and 2022. Some data for 2022 were incomplete due to ongoing treatment, emphasizing the importance of understanding the dynamics of demolition rates or surfaces to identify data gaps or errors. Historical trajectories of C&D permits were quantified and analyzed, revealing over 21,000 permits granted from 2013 to 2022, categorized by site type (new construction, rehabilitations, prior declarations, and demolitions). Construction sites during this period covered approximately 3,345,948 m2, constituting 20% of the MEL's building stock, while demolition sites amounted to 1,977,911 m2, equivalent to 5% of the total area of buildings in the metropolis. Employing GIS allowed for a spatial analysis, visualizing data by municipality, urban fabric, and year. The analysis highlighted territories with high and low potential for demolition and construction, as well as the most impacted urban fabrics and dynamic periods. The article discusses potential crisis impacts (e.g., COVID-19 or economic downturns) and the implications of incomplete data. Finally, the study demonstrates how these findings can be utilized to quantify C&D waste, leveraging GIS and the production rate calculation method (GRC). [ABSTRACT FROM AUTHOR]

Postdisaster recovery efforts of damaged civil infrastructure systems need to be optimized in order to alleviate the adverse impacts of natural disasters on local societies and economies. This paper presents an innovative framework that integrates two newly developed models for resource utilization and multiobjective optimization that are designed to optimize these recovery efforts. The developed models provide new and unique capabilities, including (1) allocating limited reconstruction resources to competing recovery projects, (2) estimating the reconstruction duration and cost associated with implementing specific recovery plans, and (3) generating optimal trade-offs between minimizing the reconstruction duration and cost. An application example is analyzed to evaluate the performance of the developed models and demonstrate their capabilities in identifying a wide spectrum of optimal reconstruction plans, where each provides a unique and nondominated trade-off between minimizing the recovery duration and cost. This allows decision makers in emergency management agencies to select and implement reconstruction plans that address various societal and economical needs in the aftermath of natural disasters. DOI: 10.1061/(ASCE)ME.1943-5479.0000024 CE Database subject headings: Resource allocation; Optimization; Reconstruction; Infrastructure; Construction management; Natural disasters; Disaster recovery. Author keywords: Resource allocation; Optimization; Recovery planning; Reconstruction efforts; Project planning; Civil infrastructure systems; Construction management.

The limited availability of reconstruction resources is one of the main challenges that often confront postdisaster recovery of damaged transportation networks. This requires an effective and efficient deployment and utilization of these limited resources in order to minimize both the performance loss of the damaged transportation network and the reconstruction costs. This paper presents the development of a robust model for planning postdisaster reconstruction efforts that is capable of: (1) optimizing the allocation of limited reconstruction resources to competing recovery projects; (2) assessing and quantifying the overall functional loss of damaged transportation networks during the recovery efforts; (3) evaluating the impact of limited availability of resources on the reconstruction costs; and (4) minimizing the performance loss of transportation networks and reconstruction costs. The model utilizes the user equilibrium algorithm to enable the assessment of the transportation network performance losses and a multiobjective genetic algorithm to enable the generation of optimal tradeoffs between the two recovery planning objectives. An application example is analyzed to demonstrate the use and capabilities of the recovery planning model. DOI: 10.1061/(ASCE)CO.1943-7862.0000070 CE Database subject headings: Planning; Resource allocation; Optimization; Reconstruction; Transportation networks; Construction management; Network analysis.

This paper presents a multiobjective optimization model that provides new and unique capabilities including generating and evaluating optimal/near-optimal construction resource utilization and scheduling plans that simultaneously minimize the time and maximize the profit of construction projects. The computations in the present model are organized in three major modules: (1) a scheduling module that develops practical schedules for construction projects; (2) a profit module that computes the project profit; and (3) a multiobjective module that searches for and identifies optimal/near optimal trade-offs between project time and profit. A large-scale construction project is analyzed to illustrate the use of the model and to demonstrate its capabilities in generating and visualizing optimal trade-offs between construction time and profit. DOI: 10.1061/(ASCE)CO.1943-7862.0000031 CE Database subject headings: Algorithms; Optimization; Construction industry; Profits; Scheduling.

This paper presents an augmented Lagrangian genetic algorithm model for resource scheduling. The algorithm considers scheduling characteristics that were ignored in prior research. Previous resource scheduling formulations have primarily focused on project duration minimization. Furthermore, resource leveling and resource-constrained scheduling have traditionally been solved independently, The model presented here considers all precedence relationships, multiple crew strategies, total project cost minimization, and time-cost trade-off. In the new formulation, resource leveling and resource-constrained scheduling are performed simultaneously. The model presented uses the quadratic penalty function to transform the resource-scheduling problem to an unconstrained one. The algorithm is general and can be applied to a broad class of optimization problems. An illustrative example is presented to demonstrate the performance of the proposed method. DOI 10.1061/(ASCE)0733-9364(2004) 130:6(869) CE Database subject headings: Construction management; Algorithms; Scheduling; Mathematical programming.

This paper presents a nonserial dynamic programming formulation for the scheduling of linear projects with nonsequential activities. One of the major advantages of the approach presented is its ability to handle both serial and nonserial linear projects with activities performed with variable crew formations. The presented formulation determines the optimum crew size for production activities that lead to the minimum project total cost. An example project is provided in order to illustrate the computational steps, validate the calculation algorithm, and show the capabilities of the proposed method.

This paper presents a design optimization method for all-wood concrete-slab forms. This procedure was formulated to provide for a safe slab-form design with minimum cost. It considers in its design process the cost of each slab-form component (sheathing, joist, stringer, and wood shore) and all available combinations of slab-form components. The performance of the optimum design method is compared to that of the traditional design method, which uses design charts/tables. The optimum design method was found to have a potential cost savings over the traditional design method. A study was conducted to confirm these cost savings. The results of the study show that cost savings as high as 9.9% were achieved by using the design optimization method.

Accumulations of worn-out automobile tires create fire and health hazards. As a possible solution to the problem of scrap-tire disposal, an experimental study was conducted to examine the potential of using tire chips and crumb rubber as aggregate in portland-cement concrete. This paper examines strength and toughness properties of concrete in which different amounts of rubber-tire particles of several sizes were used as aggregate. The concrete mixtures exhibited lower compressive and splitting-tensile strength than did normal concrete. However, these mixtures did not demonstrate brittle failure, but rather a ductile, plastic failure, and had the ability to absorb a large amount of plastic energy under compressive and tensile loads. A mathematical model is used to describe the effects of rubber aggregate on the compressive and tensile strength reduction of concrete.

Growing piles of discarded tires create fire and health hazards. Current disposal methods are wasteful and costly. This paper presents the results of an investigation into the potential of shredded tires as fill material in road construction. A test road was built to study the constructability, durability, and performance of tire chips as a new construction material. The road was made up Of six sections to examine the effects of (1) Tire-chip size; (2) method of placement; and (3) soil-cap thickness on road performance. Tbe field operation proved that use of shredded tires in road construction Poses no major handling or placement problems. However, the high compressibility of tire chips and their tendency shift laterally under compaction equipment need to be noted. The performance of the test road was monitored under freeze-thaw conditions and under service loads. The road showed acceptable performance with moderate maintenance requirements and minimum undesirable effects on ground water quality under the tested conditions.