Institutional-Repository, University of Moratuwa
Welcome to the University of Moratuwa Digital Repository, which houses postgraduate theses and dissertations, research articles presented at conferences by faculties and departments, university-published journal articles and research publications authored by academic staff. This online repository stores, preserves and distributes the University's scholarly work. This service allows University members to share their research with a larger audience.
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Recent Submissions
item: Article-Full-text
Unveiling barriers in the clouds: environmental, regulatory, and technical constraints on UAV operations in highland urban landscape
(Faculty of Graduate Studies) Thavarasa, H; Thibbotuwawa, A
Unmanned Aerial Vehicles (UAVs) have garnered considerable attention in recent years due to their integration across diverse industries, including lo¬gistics and disaster management. Challenges such as limited accessibili¬ty to remote or hazardous locations, and the inability to perform real-time monitoring and situational analysis, have been effectively addressed through the deployment of UAV technologies [1]. Operating UAVs within ur¬ban environments presents several challenges and constraints. Regulatory requirements, the presence of numerous obstacles, air pollution, and en¬ergy consumption inefficiencies have prompted researchers to investigate methods for optimizing UAV flight routes [1] [2] [3]. Nevertheless, these op¬timizations may not be directly transferable to UAV operations in highland urban environments due to a variety of additional constraints. Highland urban landscapes were selected because their steep terrain and variable weather create uniquely complex operational conditions. UAVs are used for their flexibility, affordability, and ability to capture high-resolution data in hard-to-reach areas. Other platforms like satellites or manned aircraft lack the needed detail, maneuverability, or cost-effectiveness. This study seeks to systematically identify and analyse these constraints, which are classi¬fied into three principal domains: environmental, regulatory, and technical.
item: Article-Full-text
How energy-efficient UAVs are transforming pesticide spraying
(Faculty of Graduate Studies) Thavarasa, H; Thibbotuwawa, A
Unmanned Aerial Vehicle (UAV), often called “drones”, is one of the modern technologies widely used in different fields such as real-time monitoring, remote sensing, disaster relief operations, delivery of goods, security and surveillance, precision agriculture, and civil infrastructure inspection.
In agriculture, UAVs are transforming the modern agricultural practices through enhanced efficiency, precision, and reduced labour intensity. Due to global population growth, global food demand increases therefore UAVs are becoming important tools in precision agriculture [1]. UAVs are integrated in farming operations and support a range of tasks including crop monitoring, pesticide and fertilizer spraying, seed sowing and growth evaluation. Equipped with high-resolution cameras and cutting-edge sensors, UAVs can gather real-time data on pest infestations, soil condition, and crop health. From those data about where and when apply inputs such as fertilizers or pesticides, and water ensuring better resource efficiency.
item: Article-Abstract
Tensile and compressive strengths of local Sri Lankan bamboo species
(The Institution of Engineers Sri Lanka) Allalagoda, SVP; Karunarathne, DPYK; Jayasinghe, MTR; Fernando, PLN; Heratht, HMST
The construction industry in Sri Lanka is currently searching for sustainable and cost effective alternatives to conventional materials like concrete and steel. Bamboo has emerged as a promising alternative, and it is widely used in construction in many countries. Although Sri Lanka has abundant bamboo forests, their potential is largely underutilised in the industry, with most of the bamboo being used only for scaffolding. One of the main barriers to using bamboo as a construction material is the lack of knowledge regarding the key mechanical properties of local bamboo species.This study aims to evaluate the critical mechanical properties of several bamboo species found in Sri Lanka, including Bambusa vulgaris var. vittata, Bambusa vulgaris, Dendrocalamus giganteus, and Dendrocalamus hookeri. A total of 174 specimens were tested for compressive strength parallel to the grain, and 150 specimens were tested for tensile strength parallel to the grain, following the ISO 22157-1:2019 standard. The results indicate that the average compressive strength and tensile strength for all species exceeded 42 N/mm2 and 87 N/mm2, respectively. These findings demonstrate that bamboo species used in the study exhibit similar compressive strength to normal concrete, and their tensile strengths are adequate for construction purposes, highlighting their potential as a viable alternative material in Sri Lanka's construction industry.
item: Article-Abstract
Investigating the effect of bearing stiffeners on the web crippling capacity of lipped channel beams
(The Institution of Engineers Sri Lanka) Subhasinghe, SPSM; Suganiyah, T; Atulugama, IUM; Abeysekara, AWANR; Weragoda, VSC; Karunaratne, RDPYK; Herath, HMST
Cold-Formed Steel (CFS) sections are widely utilised in the construction industry due to their significant structural and economic advantages. However, due to their thin-walled geometry, they are susceptible to local failures, such as web crippling. This failure mode is further intensified by the service holes used for utilities. This study investigates the web crippling behaviour of cold-formed steel lipped channel beams under Interior Two Flange (ITF) loading, focusing on the influence of web perforations and transverse stiffeners. Current design standards do not adequately address the combined effects of web openings and stiffeners under TIF loading. Sixteen lipped channel specimens with varying stiffener configurations and web openings were fabricated and tested under TIF loading according to the American Iron and Steel Institute (AISI 5909) standard. The experimental program measured load-deflection responses, ultimate web crippling capacities, and failure modes for each configuration. Results showed that using transverse stiffeners can increase the web crippling capacity by 58.1-117.6% compared to beams without stiffeners. When beams contain web holes, the web crippling strength is significantly reduced, especially when aligned beneath the bearing plate. However, transverse stiffeners can restore the capacity by 60.2-119.4%, depending on the location of the web hole. These findings provide valuable experimental data and insights for the development of improved design guidelines.
item: Article-Abstract
predictions of optimum design quantities for reinforced concrete beam-slab system through reutilization of empirical data from constructed projects in Sri lanka
(The Institution of Engineers Sri Lanka) Saranja, K; Mallikarachchi, HMYC; Herath, HMST
Decisions in the Preliminary Design Stage (PDS) highly influence the final structural design deliverables. However, the PDS procedures are generally recursive, labour-intensive and time consuming. Expert-driven designs typically dominate at this stage to achieve structurally optimized solutions, yet the reutilization of earlier design information remains limited. Besides,as the floor system is the major structural component of a multi-storied building, addressing its embodied energy demands requires close attention to yield a sustainably optimized solution. To overcome the limitations of traditional practices in the PDS, this study employs an Artificial Neural Network (ANN), as a learning based method to predict design quantities, aiming for optimization of reinforced-concrete beam-slab systems of multi-storied buildings. The models were developed using the data collection from the constructed buildings in Sri Lanka,following standard machine learning protocols. The proposed best models are recorded predictions with R2 values above 0.8, demonstrating superior performance in the context of heterogeneous real-world data.The proposed ANN-based numerical model streamlines the selection of the best-optimized floor system by analysing a range of alternatives encapsulating performance, economic and environmental criteria. By capturing and reapplying expert knowledge from structural data and drawings, which have been previously evaluated and accepted by experienced engineers, the approach enhances decision-making in the PDS.