Faculty of Engineering

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Open Access
Erratum to “Using social and economic factors for ranking pavement maintenance and rehabilitation projects
(Elsevier, 2022-01) Gunathilaka, S; Amarasingha, N
Current pavement maintenance and rehabilitation project prioritization in Sri Lanka considers only economic factors while neglecting social, political, and environmental factors. In this study, the Analytic Network Process (ANP), which can be used as a multicriteria decision-making tool, was utilized for the evaluation of three different pavement maintenance and rehabilitation projects in Sri Lanka. Social and economic factors that affected the three projects were considered and the inner and outer dependencies among them were evaluated and weighted. Pairwise comparisons were conducted complemented by interviews of transportation experts from the Road Development Authority (RDA) of Sri Lanka. Given that the RDA’s current method only considers economic factors, our results highlighted differences between the two methods. Therefore, ANP could be recommended for prioritizing pavement maintenance and rehabilitation projects in Sri Lanka
Open Access
Comparison of Instrumented Pile Load Test Results with Finite Element Simulation
(World Congress on Civil, Structural, and Environmental Engineering, 2022-04-10) Diyes, G. H. I.; Thilakasiri, H.S.; de Silva, L.I.N
Due to the proximity of the bedrock, rock socketed bored and cast in-situ piles are used to support the heavy super structure loads from the high-rise structures transferring to bedrock. In order to design single piles or group of piles, it is very important to know the carrying capacity of the bedrock in terms of skin friction distribution along the pile shaft and the load carried by the pile toe. Such information can be obtained by using the instrumented pile load tests but the instrumented pile load tests are expensive and not always carried out in most of the piling sites in Sri Lanka. In this study, it was aimed to find out the carrying capacity of cast in-situ bored single piles using commonly used finite element software PLAXIS 2D and compare the results with the instrumented pile load test results obtained in the field. Prior to the use of software package based on finite element analysis to find out the carrying capacity of the pile, the accuracy of the model used was verified by the results instrumented pile load test and the nearby borehole test results. Further, the differences and the difficulties of the interpretation of results with their potential reasons were discussed within the study. In the current study, the soil and rock properties were used from the nearby borehole results. It was shown that the best match results with the field instrumented pile load tests for weathered rocks were obtained when the elastic modulus for rock layers were twice the value suggested by Hong Kong geo guidelines (Geo,2006) whereas the best match results with instrumented pile load test results were given when half the value of the Young’s modulus of rock suggested by the Hong Kong geo guidelines (Geo,2006).
Open Access
Investigating applicability of sawdust and retro-reflective materials as external wall insulation under tropical climatic conditions
(Springer link, 2022-04-19) Dharmasena, P; Meddage, D. P. P; Mendis, S
Buildings require energy to maintain their performance. In consequence, built environments cause a surge in the world’s energy demand. Providing passive measures is an efective method of optimizing operational energy usage. In this study, we propose insulation materials (thermal barrier type and resistive insulation) for the walls of a building. Experiments were performed on small-scale physical models constructed with; (a) no insulation, (b) sawdust–cement mortar, and (c) retrorefective (RR) material for external walls. In addition, regression models were developed to predict indoor air temperature with insulation. Subsequently, associated operational energy-saving and decrease in emissions were estimated for each material. The comparison reveals RR (sawdust–cement mortar) is efective in warm (overcast) climatic conditions. Developed regression models have shown a good agreement with experimental results (R>0.8). Moreover, sawdust–cement mortar (RR) materials contributed a 9% (13.4%) reduction in operational energy and a 9% (13.3%) decrease in CO2 emissions. The project highlights the potential to utilize sawdust—a waste material—and RR material as wall insulation to decrease intense operational energy demand.
Open Access
SUCCESSFUL DELIVERY OF PUBLICPRIVATE PARTNERSHIP (PPP) IN THE CONSTRUCTION PROJECTS OF SRI LANKAN HIGHER EDUCATION SECTOR
(https://ciobwcs.com, 2022-06-24) Kandawinna, N; Mallawaarachchi, H; Vijerathne, D
To gain economic advantages in the competitive world, governments tend to adopt new financing methods in construction projects. Accordingly, Public-Private Partnership (PPP) projects are a popular choice mainly due to the reduction in transaction cost and innovation. PPP projects have spread from the typical use on infrastructure projects such as airports, roads, railways, ports, and water sanitation to the more recent use for projects in the higher education sector such as universities and colleges. Thus, adopting PPP for the higher education sector related construction projects in Sri Lanka is vital to consider. Accordingly, this research aims to observe the Critical Success Factors (CSF) for the successful delivery of PPP projects in the construction projects of the higher education sector in Sri Lanka. A comprehensive literature review was first conducted to identify the CSFs of PPP in higher education construction projects and 22 CSFs were identified. The survey method was used under quantitative phenomenon since this research required evaluating the identified CSFs. The identified factors were evaluated through a questionnaire survey, which was conducted among the 30 selected professionals who are aware on PPPs, such as Quantity Surveyors, Project Managers, Government Professionals, and Academic Professionals. As the key findings derived through analysis, “communication between parties”, “transparency in the procurement process”, financial capability and support”, “project technical feasibility” and “appropriate risk allocation and risk-sharing” were determined as the top five CSFs for PPP projects in the higher education sector related construction projects in Sri Lanka. Furthermore, strategies were also proposed to ensure the successful implementation of CSFs in the higher education sector in Sri Lanka.
Open Access
CIRCULAR ECONOMY (CE) BASED MATERIAL SELECTION: DEVELOPMENT OF A CE-BASED ‘10R’ EVALUATION FRAMEWORK FOR BUILDING CONSTRUCTION PROJECTS IN SRI LANKA
(https://ciobwcs.com, 2022-06-24) Wanaguru, K; Mallawaarachchi, H; Vijerathne, D
The building construction industry is globally identified as one of the major consumers of materials. Thus, the material wastage in building construction projects is very excessive. In the Sri Lankan construction industry, it was identified that the main reason for generating material wastage is the absence of proper material selection criteria. The concept of Circular Economy (CE) has been obtained the world attention in reducing material wastage in the construction industry as it targets zero waste and pollution throughout the lifecycle of materials. Applying CE principles in the material selection not only reduces the wastage of materials but also reduces the use of virgin materials. Hence, this research aimed for developing a CE-based 10R evaluation framework for materials selection in order to reduce the wastage of materials in building construction projects in Sri Lanka. A comprehensive literature review was first conducted to review the concept of CE, CE principles and its importance for reducing material wastage in the construction industry. Deductive approach was chosen as the suitable research approach in this study. Survey method was applied as the suitable research strategy under quantitative phenomenon. A questionnaire survey was conducted with a conveniently selected sample of 58 industry professionals to collect the data. The collected data were analysed by using Weighted Mean Average (WMA) technique. As key findings derived through analysis, the level of importance of each CE principle for selection of materials was determined. Accordingly, the CE-based 10R evaluation framework for material selection was developed as the main implication of this research. Various strategies, such as reusing demolition materials, adopting prefabricated building components, developing plans to on-site recycle and using alternative materials were also proposed to implement the all identified CE principles assuring a successful application of the developed framework.
Open Access
EFFECT OF COVID-19 ON THE SMALL-SCALE CONSTRUCTION COMPANIES: THE CASE OF COLOMBO DISTRICT, SRI LANKA
(Ceylon Institute of Builders, 2022-06-26) Gunarathna, N; Namarathna, C. P
COVID-19 is a global pandemic that has wreaked havoc on the lives of many individuals and has had a severe impact on the global economy. During this crisis, small and medium-scale businesses suffer the most and are the least prepared among all companies as per the previous studies done in other parts of the world. The majority of the small-scale construction firms in Sri Lanka act as subcontractors and generate job opportunities for a considerable number of people and are able to create a multiplier effect on the whole economy. However, it was observed that they are more vulnerable to the adverse impact of the pandemic. Thus, the principal goal of this research is to explore possible survival strategies to overcome critical financial issues of small-scale construction companies during the ongoing COVID-19 pandemic in Sri Lanka. A mixedmethod approach was adopted to gather the data for the study. A comprehensive literature review was carried out to identify the impact of COVID-19 on both global and local construction industries. The data for this study was gathered using semi-structured interviews and a comprehensive questionnaire survey with small scale construction company owners and construction industry professionals. The findings highlighted the key financial issues faced by the small-scale construction companies due to the pandemic including delays in client payments, supply chain management issues, frequent price escalation of construction materials, and inability to repay loans. The respondents suggested creating partnerships with financially strong companies, reduction of unwanted expenses, modifying supply chain channels and agreements, and ensuring business continuity plans as the strategies to be used to overcome the financial burden that occurred due to the pandemic.
Open Access
IMPLEMENTING SAFE WORKING CYCLE (SWC) CONCEPT AMIDST THE COVID-19 CRISIS IN SRI LANKA
(Ceylon Institute of Builders, 2022-06-26) Rasanjana, H.P; Allis, C
The phenomenon of COVID-19 has introduced critical challenges in the architecture, engineering, and the entire construction industry. A safe Working Cycle is a Japanese concept. It incorporates to enhances the effective implementation of safety management systems, thereby helping to prevent health and safety issues. This research mainly aims at identifying the strategies for overcoming barriers to implementing the Safe Working Cycle (SWC) concept during the COVID-19 pandemics in Sri Lanka. The research study focused more on reducing health-related illnesses caused by COVID-19 than on the other physical safety issues at the construction site. In such a critical health issue, the protection of human resources, an essential part of the construction industry, should be prioritized. The aim of the Study was reached through the sequential mixed method. The semi-structured expert interviews were initially conducted, and after that questionnaire survey was achieved among health and safety officers in construction projects in Sri Lanka. In the semi-structured interviews, data were analyzed using Nvivo thematic analysis software and questionnaire survey; M.S. Excel analyzed the collected data. Following the findings, several potential barriers were arisen to implementing the SWC concept in the Sri Lankan construction industry: including limited Budget allocation, poor safety attitude, limited land space, strict project schedules, and unawareness of workers. Further, this Study also indicated several potential practical strategies to overcome these barriers identified for SWC implementation. Such as; Implementing the COVID-19 bio bubble concept, Organizing regular toolbox meetings, demonstrating sign boards specific to this new concept, arranging separate systematic time slots, buildup a good communication network. The safe Working Cycle (SWC) is not currently practised in Sri Lankan construction culture. However, health and safety professionals are familiar with almost every aspect of the Safe Working Cycle (SWC); therefore, it is possible to put this into practice in the Sri Lankan construction industry. © 2022, Ceylon Institute of Builders
Open Access
Influence of Crumb Rubber and Coconut Coir on Strength and Durability Characteristics of Interlocking Paving Blocks
(MDPI, 2022-07-13) Gamage, S; Palitha, S; Meddage, D. P. P; Mendis, S; Azamathulla, H. M; Rathnayake, U
Interlocking Paving Blocks (IPB) are, nowadays, a widely used construction material. As a result of the surge in demand for IPBs, alternative materials have been investigated to be used for IPBs. This study investigated the strength and durability characteristics (compressive strength, split tensile strength, density, water absorption, skid resistance, and abrasion resistance) of IPBs in the presence of (waste materials) crumb rubber (CR) and coconut coir fibers (CCF). Both compressive and split tensile strength increased in the presence of CCF to a certain extent. CR-based IPBs showcased an increase in skid resistance that satisfied both SLS 1425 and BS EN 1338 specifications. Abrasion depths of CR-based and CCF-based samples show a comparable increase in values when the respective fraction (CR or CCF) increases. Therefore, this research fills the knowledge gap, highlighting the importance of incorporating waste materials (CR and CCF) for the IPB industry rather than open dumping.
Open Access
Analysis of Meandering River Morphodynamics Using Satellite Remote Sensing Data—An Application in the Lower Deduru Oya (River), Sri Lanka
(MDPI, 2022-07-16) Basnayaka, V; Samarasinghe, J. T; Gunathilake, M. B; Muttil, N; Hettiarachchi, D. C; Abeynayaka, A; Rathnayake, U
River meandering and anabranching have become major problems in many large rivers that carry significant amounts of sediment worldwide. The morphodynamics of these rivers are complex due to the temporal variation of flows. However, the availability of remote sensing data and geographic information systems (GISs) provides the opportunity to analyze the morphological changes in river systems both quantitatively and qualitatively. The present study investigated the temporal changes in the river morphology of the Deduru Oya (river) in Sri Lanka, which is a meandering river. The study covered a period of 32 years (1989 to 2021), using Landsat satellite data and the QGIS platform. Cloud-free Landsat 5 and Landsat 8 satellite images were extracted and processed to extract the river mask. The centerline of the river was generated using the extracted river mask, with the support of semi-automated digitizing software (WebPlotDigitizer). Freely available QGIS was used to investigate the temporal variation of river migration. The results of the study demonstrated that, over the past three decades, both the bend curvatures and the river migration rates of the meandering bends have generally increased with time. In addition, it was found that a higher number of meandering bends could be observed in the lower (most downstream) and the middle parts of the selected river segment. The current analysis indicates that the Deduru Oya has undergone considerable changes in its curvature and migration rates.
Embargo
Wireless Power Transfer for Cardiac Pacemaker
(IEEE Computer Society, 2022-08-17) Uthayakumar, U; Jayaweera, Y
Cardiac pacemaker is an electronic device used to regulate the heartbeat of patients suffering with congenital heart defects. Considering the limitations in lifespan of current cardiac pacemaker battery, a wireless charging mechanism for cardiac pacemaker is proposed in this paper. Circuitry model and electromagnetic geometry is developed using Ansys Maxwell and Ansys High-Frequency Structure Simulator (HFSS) software to analyze three main technical issues such as: implantation, efficiency and safety. Specific Absorption Rate (SAR) and induced electric field in a 3-D model human body is evaluated by numerical analysis and simulation to ensure that the developed system adheres to safety limits proposed by Institute of Electrical and Electronics Engineers (IEEE) standard and International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines.
Open Access
Statistical Evaluation and Trend Analysis of ANN Based Satellite Products (PERSIANN) for the Kelani River Basin, Sri Lanka
(Hindawi, 2022-08-31) Perera, H; Gunathilake, M. B; Panditharathne, R; Al-mahbashi, N; Rathnayake, U
Satellite-based precipitation products, (SbPPs) have piqued the interest of a number of researchers as a reliable replacement for observed rainfall data which often have limited time spans and missing days. The SbPPs possess certain uncertainties, thus, they cannot be directly used without comparing against observed rainfall data prior to use. The Kelani river basin is Sri Lanka’s fourth longest river and the main source of water for almost 5 million people. Therefore, this research study aims to identify the potential of using SbPPs as a different method to measure rain besides using a rain gauge. Furthermore, the aim of the work is to examine the trends in precipitation products in the Kelani river basin. Three SbPPs, precipitation estimation using remotely sensed information using artificial neural networks (PERSIANN), PERSIANN-cloud classification system (CCS), and PERSIANN-climate data record (CDR) and ground observed rain gauge daily rainfall data at nine locations were used for the analysis. Four continuous evaluation indices, namely, root mean square error (RMSE), (percent bias) PBias, correlation coefficient (CC), and Nash‒Sutcliffe efficiency (NSE) were used to determine the accuracy by comparing against observed rainfall data. Four categorical indices including probability of detection (POD), false alarm ratio (FAR), critical success index (CSI), and proportional constant (PC) were used to evaluate the rainfall detection capability of SbPPs. Mann‒Kendall test and Sen’s slope estimator were used to identifying whether a trend was present while the magnitudes of these were calculated by Sen’s slope. PERSIANN-CDR performed well by showing better performance in both POD and CSI. When compared to observed rainfall data, the PERSIANN product had the lowest RMSE value, while all products indicated underestimations. The CC and NSE of all three products with observed rainfall data were also low. Mixed results were obtained for the trend analysis as well. The overall results showed that all three products are not a better choice for the chosen study area.
Embargo
An Incentivized and Optimized Dynamic Mechanism for Demand Response for Managing Voltage in Distribution Networks
(IEEE, 2022-09-05) Rahman, M. M; Arefi, A; Shafiullah, G. M; Hettiwatte, S; Azizivahed, A; Muyeen, S. M
The voltage regulation in distribution networks is one of the major obstacles when increasing the penetration of distributed generators (DGs) such as solar photovoltaics (PV), especially during cloud transients, causing potential stress on network voltage regulations. Residential demand response (DR) is one of the cost-effective solutions for voltage management in distribution networks. However, the main barriers of DR implementation are the complexities of controlling a large number and different types of residential loads, satisfying customers’ preferences and providing them fair incentives while identifying the optimum DR implementation locations and sizing as well as cooperating with the existing network equipment for the effective voltage management in the networks. A holistic and practical approach of DR implementation is missing in the literature. This study proposes a dynamic fair incentive mechanism using a multi-scheme load control algorithm for a large number of DR participants coordinating with the existing network equipment for managing voltage at medium voltage (MV) networks. The multi-scheme load control is comprised of short-interval (10-minute) and long-interval (2-hour) DR schemes. The dynamic incentive rates are optimized based on the energy contribution of DR participating consumers, their influence on the network voltage and total power loss improvement. The proposed method minimizes the DR implementation cost and size, fairly incentivizes the consumers participating in the DR and priorities their consumption preferences while reduces the network power losses and DGs’ reactive power contributions to effectively manage the voltage in the MV networks. An improved hybrid particle swarm optimization algorithm (IHPSO) is proposed for the load controller to provide fast convergence and robust optimization results. The proposed approach is comprehensively tested using the IEEE 33-bus and IEEE 69-bus networks with several scenarios considering a large number of DR participants coordinated with the DGs and on-load tap changer (OLTC) in the networks.
Embargo
Smart Irrigation System for Domestic Homes
(IEEE, 2022-09-05) Rajapaksha, I; Gamage, T; Eranga, I; Dharmasena, A; Gamage, K
This research presents the designing of a smart irrigation system to automatically supply water and fertilizer to different plants depending on each plant ’s individual requirement and the integration of this smart irrigation system to a domestic home. The microcontroller was programmed to operate under two modes. Fully automated and semi-automated. These two modes give all the monitoring information to the user in real-time, while fully automated mode provides water and fertilizer to the plants calculating optimum conditions with minimum human interaction. Microcontroller was programmed to (1) analyze and process the received input data from soil moisture sensors, humidity and temperature sensors, (2) check the activated mode and other user settings, and (3) control the valves to water or fertilize the plants accordingly. Microcontroller and the IoT device maintain communication to receive or send data to the user through internet. A web interface was developed to display sensor data and with a control interface for the user. The user can connect to the system through Wi-Fi to access the web interface. By using the controls, soil moisture, temperature and humidity thresholds can be changed, and watering or fertilization systems can be activated. For data analysis and flowrate simulations, ‘SolidWorks’ was used. Using the same software, the enclosures and other hardware components needed to store the microcontroller, the Wi-Fi module, the power supply, and connector array of sensors were designed, 3D printed, and the complete system was assembled and tested.
Open Access
Spatio-Temporal Rainfall Variability and Concentration over Sri Lanka
(Hindawi, 2022-09-28) Pawar, U; Karunathilaka, P; Rathnayake, U
Changes in precipitation patterns significantly affect flood and drought hazard management and water resources at local to regional scales. Therefore, the main motivation behind this paper is to examine the spatial and temporal rainfall variability over Sri Lanka by Standardized Rainfall Anomaly Index (SRAI) and Precipitation Concentration Index (PCI) from 1990 to 2019. The Mann–Kendall (MK) trend test and Sen’s slope (SS) were utilized to assess the trend in the precipitation concentration based on PCI. The Inverse Distance Weighting (IDW) interpolation method was incorporated to measure spatial distribution. Precipitation variability analysis showed that seasonal variations are more than those of annual variations. In addition, wet, normal, and dry years were identified over Sri Lanka using SRAI. The maximum SRAI (2.27) was observed for the year 2014 for the last 30 years (1990–2019), which shows the extremely wet year of Sri Lanka. The annual and seasonal PCI analysis showed moderate to irregular rainfall distribution except for the Jaffna and Ratnapura areas (annual scale-positive changes in Katugastota for 21.39% and Wellawaya for 17.6%; seasonal scale-Vavuniya for 33.64%, Trincomalee for 31.26%, and Batticaloa for 18.79% in SWMS). The MK test, SS-test, and percent change analyses reveal that rainfall distribution and concentration change do not show a significant positive or negative change in rainfall pattern in Sri Lanka, despite a few areas which experienced significant positive changes. Therefore, this study suggests that the rainfall in Sri Lanka follows the normal trend of precipitation with variations observed both annually and seasonally.
Open Access
A NOVEL TREATMENT FOR DETERMINING THERMAL CONDUCTIVITY OF THE SOIL SUBSTRATES FOR SELECTING SUSTAINABLE GROWING MEDIUMS IN TERMS OF THERMAL RESISTANCE
(University of Montenegro, 2022-09-30) Kader, S; Jaufer, L
The Thermal conductivity of the soil is important to determine the horticultural performance of growing medium. Microclimatic features influence the viability of soil mixtures for vegetation. The goal of this study is to assess the heat conductivity of soil mixture samples comprising Coir, Biochar, Sawdust, Wood bark, and Compost in order to discover the best growth medium in terms of thermal resistance. Specimens were prepared by mixing 60% of raw materials with 40% topsoil and moulded into cylinders. Each sample were converted into semi solids and undergone for thermal conductivity apparatus measurements. Thermal conductivity of each specimen was determined using mathematical analysis based on experimental readings. The calculated results were used to deduce thermal resistance. Thermal conductivity values of all specimens were observed in the range from 0.64 W/mK to 0.91 W/mK. The maximum and minimum thermal conductivity magnitudes were exhibited by Sawdust (60:40) and Wood bark (60:40) respectively. In terms of suitability as a growing medium, Wood bark (60:40) contains highest thermal resistance while the lease thermal resistance was determined in Sawdust (60:40) due to its high thermal conduction. This research concludes that Wood bark (60:40) is the most convincing substrate in terms of thermal sustainability. © 2022, University of Montenegro. All rights reserved.
Open Access
Implementation of water–saving agro technologies and irrigation methods in agriculture of Uzbekistan on a large scale as an urgent Issue
(Springer Science and Business Media Deutschland GmbH, 2022-10) Rathnayake, U; Chathuranika, I; Khaniya, B; Neupane, K; Rustamjonovich, K. M
Usable water resource is limited, even though 71% of world is covered by water. Therefore, enough conficts to the usable water can be found throughout the world. Usable water for irrigation is a top priority, probably it would be seconding only to the drink water supply. However, prioritizing one usage over another is challenging to many stakeholders. Therefore, sustainable water usage is essential to avoid any conficts among the stakeholders; nevertheless, highly challenging in the developing world. Therefore, this paper discusses the water saving irrigation practices and ways to use agriculture around the world, including Uzbekistan. Relying on the ancient irrigation technologies used by ancestors and also modern irrigation methods, diferent irrigation water management technologies are presented to apply for various weather conditions and water availability situations. Suitable irrigation practices are discussed based on the water needs especially the arid countries, such as Uzbekistan. The results of an experiment conducted for hilly areas of Uzbekistan using “mulching” agro-technology is presented along with its suitability for Uzbekistan. Therefore, the expectations of sustainable water usage for irrigation is proposed.
Open Access
Planform Changes in the Lower Mahaweli River, Sri Lanka Using Landsat Satellite Data
(MDPI, 2022-10-03) Basnayaka, V; Samarasinghe, J. T; Gunathilake, M. B; Muttil, N; Rathnayake, U
Major development projects along rivers, like reservoirs and other hydraulic structures, have changed not only river discharges but also sediment transport. Thus, changes in river planforms can be observed in such rivers. In addition, river centerline migrations can be witnessed. The Mahaweli River is the longest in Sri Lanka, having the largest catchment area among the 103 major river basins in the country. The river has been subjected to many development projects over the last 50 years, causing significant changes in the river discharge and sediment transport. However, no research has been carried out to evaluate the temporal and spatial changes in planforms. The current seeks to qualitatively analyze the river planform changes of the Lower Mahaweli River (downstream to Damanewewa) over the past 30 years (from 1991 to 2021) and identify the major planform features and their spatiotemporal changes in the lower Mahaweli River. Analyzing the changes in rivers requires long-term data with high spatial resolution. Therefore, in this research, remotely sensed Landsat satellite data were used to analyze the planform changes of Lower Mahaweli River with a considerably high resolution (30 m). These Landsat satellite images were processed and analyzed using the QGIS mapping tool and a semi-automated digitizing tool. The results show that major changes in river Mahaweli occurred mainly in the most downstream sections of the selected river segment. Further, the river curvature was also comparatively high downstream of the river. An oxbow lake formation was observed over time in the most downstream part of the Mahaweli River after 2011. Centerline migration rates were also calculated with the generated river centerlines. It was found that the rates were generally lower than about 30 m per year, except for at locations where river meandering was observed. The main limitations of this study were the possible misclassifications due to the resolution of images and obstructions caused by cloud cover in the Landsat images. To achieve more accurate estimates, this study could be developed further with quantitative mathematical analysis by also considering the sediment dynamics of the Mahaweli River.
Open Access
Introduction of a Simple Estimation Method for Lane-Based Queue Lengths with Lane-changing Movements
(Springer, 2022-10-03) Jayatilleke, S; Wickramasinghe, V; Amarasingha, N
Trafc congestions are increased globally due to rapid urbanization and expedited economic developments in many countries. Vehicle queue is a governing aspect of trafc congestion, studied over the past decades. Most of the existing queue estimation approaches are limited to homogeneous trafc conditions. However, the trafc conditions in many developing countries are heterogeneous and are heavily infuenced by mixed vehicle composition, lane changing, and gap-flling behaviours. This study aims to estimate the queue length at signalized intersections having heterogeneous trafc conditions. The heterogeneity was assimilated with the consideration of Passenger Car Units (PCU) in the measurements of the trafc fow and the lanechanging movement within the considered road section. The infuential factors of the queue length were contemplated with the arrival fow, discharge fow, outbound lane change, inbound lane change, and signal confguration. A Vector Auto Regression (VAR) model was developed to estimate queue length, with a lag time of 15 s for each variable. The results have indicated a higher accuracy in the queue estimation as well as the practical application for prediction, constituting the trafc characteristics of the formed vehicle queue. The R squared of the VAR model was 0.97, along with a Mean Absolute Percentage Error (MAPE) of 21.55%. The model estimation results of right turning lanes were well accurate with MAPE ranging from 15 to 17%, whilst for through movement lanes, accuracy was slightly low with MAPE in the range of 23–26%. The study manifests the functionality of the developed methodology for accurate queue estimations, asserting the practical applicability of VAR models in other locations constituting mixed trafc.
Open Access
Green roof substrates—A literature review
(frontiersin, 2022-10-03) Kader, S; Chadalavada, S; Jaufer, L; Spalevic, V; Dudic, B
Green roofs are becoming increasingly popular in urban construction due to their wide array of benefits for creating a sustainable ecosystem. Many stakeholders invest in green roofs in the 21st century to enhance the environmental quality and mitigate urban ecological pollution. The substrate layer is the most important and critical component of green roof systems. The objective of the review study is to present the important information regarding the required elements that need to be considered for substrate selection of green roofs by critically reviewing the scientifically published articles. Research findings from past studies relevant to green roofs, vegetation and selective substrate parameters were extensively discussed under different topics related to water retention, drought resistance and related physico-chemical parameters. The generalities in past research articles were presented and special focus was provided on specific research articles those presented novelty regarding green roof substrates. Furthermore, the hotspots in all the considered research articles were commentatively identified and the appropriate solutions were evaluated. The critical review of published research articles indicates that most of the research on green roof substrates was conducted in either controlled laboratories or greenhouses and did not provide much importance to actual field tests. Therefore, these research findings are not sufficient to obtain the realistic field outcomes of the research. Future studies on green roof substrates should need to incorporate field experiments along with classical controlled tests by adhering to standard guidelines for assimilating climatic influences in substrates. Few studies have focused on dry climates, and further research needs to be conducted on dry climates due to their high susceptibility to drought and evapotranspiration. This manuscript would be the first review article that mainly focuses on substrates for green roofs, which is a novel aspect.
Embargo
The use of plastic aggregate in concrete
(IEEE, 2022-10-04) Karunaratne, S; Zahra Ameen, C. A
Plastic waste management is a growing concern worldwide since permanent solutions are costly for third-world countries. This study explores storing plastic waste in concrete as a partial replacement of the fine aggregate to produce a useful building material. To resolve the material's lack of compressive strength, this study used HDPE chemically treated with Sodium Hypochlorite (NaOCl) and partially replaced the cement with silica fume at 7.5%, and 10% to improve the concretes Interfacial Transition Zones (ITZ). This research tests the workability, density, and compressive strength, and completes a microstructure analysis of this material to determine if structural lightweight concrete (SLWC) can be produced. The results obtained indicate that adding silica fume with chemically treated aggregate increased the compressive strength by 1.9% and 7.4% respectively in comparison to the control. Through the statistical analysis, these additions were then shown to make a significant difference in the concrete's strength. The microstructure analysis too confirmed that the quality of the ITZs had improved in these mixtures. However, the workability of these 2 mixtures was reduced by 77.4%. The study concludes that although the concrete isn't lightweight, its compressive strength can be improved to match that of conventional structural concrete.