Master of Science By Research

Permanent URI for this collectionhttp://192.248.9.226/handle/123/13944

Browse

Now showing 1 - 20 of 104

item: Thesis-Full-text
Durability of concrete produced from internal curing concrete aggregate manufactured from industrial waste
(2022) Nivojan, P; Mampearachchi, WK
Modern buildings have made extensive use of Internal Curing (IC) for high-performance concrete (HPC). Nowadays, the rise of industrial waste has numerous negative repercussions on both society and the environment. Also, the building industry has seen numerous risks on the riverbank as a result of the increased demand for sand. Consequently, these issues can be resolved and the ineffective external curing of high-performance concrete with a lower w/c ratio can be reduced by replacing the fine aggregate with internal curing concrete aggregate (ICCA) made from industrial waste. Here, ICCA has previously been created using various industrial wastes. This study intends to evaluate the mechanical properties and durability of ICC constructed using two types of ICCA generated from waste materials to partially replace fine aggregate. Tests by the broadly accepted methods of mechanical and durability evaluations, such as compressive strength, workability, statistic modulus of elasticity, surface resistivity, rapid chloride ion penetration, water permeability, saturated water absorption, and initial surface absorption were conducted for industrial mix design, and high-performance mix design. Three types of curing samples; internal curing, external curing, and non-curing, were evaluated. The effects on durability and mechanical properties of concrete with these ICCA aggregates as a replacement material for fine aggregate are reported. ICC showed a 10 to 20 percent increment in a slump, 5 to 15 percent increment in compressive strength, 9 to 12 percent reduction in static modulus of elasticity, and a 9 to 17 percent increment in surface resistivity compared to the conventional concrete. Moreover, it showed lower penetration of chloride ion permeability, and lower initial surface absorption at 28 days. Further, ICC showed a slightly higher depth of penetration and saturated absorption initially and a reduction with time. Keywords - durability, internal curing aggregate, internal curing, fine aggregate, mechanical properties, industrial waste.
item: Thesis-Full-text
Estimate characteristics of open graded friction courses by digital image analysis
(2021) Dedigamuwa, KV; Mampearachchi, WK
The application of Open Graded Friction Courses (OGFC) as a pavement material has become a suitable solution for areas with high rainfall intensities. Since, OGFC material can act as a function-oriented pavement material to enhance permeability, reduce noise, and introduce more friction, improving the properties OGFC asphalt material to meet the requirements has drawn the attention of researchers in the last few decades. It is evident that the existence of a complex interconnected void network in OGFC has directly affected the durability and the permeability of the mixture. Further, the interconnected void network entirely depends upon the internal aggregate arrangement. Therefore, the identification of the internal arrangement of aggregates is very important to understand the void structure and improve the performance of designing OGFC. The lack of availability of quality controlling tools in the industrial construction stage leads to the occurrence of defects at the service stage and most of these issues can be minimized by investigating the internal structure of OGFC. This study presents a cost effective, rapid Digital Image Processing (DIP) method to determine the internal aggregate structure and the gradations of a core sample during the design and construction stages. Further, the proposed method enables the identification and quantification of segregation variation, internal voids and material distribution along the depth of the specimen. Experimental program of the study majorly included permeability test and durability test to compare the analytical results obtained for validation and justification. The internal aggregate structure data was collected by capturing cross section images in order to introduce a feasible way of implementing a gradation analysis. The cross sectional details were analysed to obtain details of areas, lengths and coordinates by developing an algorithm in MATLAB software. MATLAB was also used to obtain 2D aggregates structures and 3D models of specimens were constructed by using the python tool “plotly” on “Anaconda” platform. This research provides fundamentals to interpret and analyse data using DIP to construct the internal aggregate structure of OGFC specimens to identify and quantify deviations by the means of gradation, segregation and voids. Keywords: Digital Image Processing, Gradation, Internal Structure, MATLAB, OGFC
item: Thesis-Abstract
Investigation of the suitability of sintered fly ash and reservoir sediment materials as a fine aggregate replacement material
(2021) Tharshigan, T; Mampearachchi, WK
Fly ash is produced as a byproduct from Lakvijaya coal power plant, Sri Lanka. The daily production of fly ash at Lakvijaya power plant is 950 – 1000 tons. Around 40% of fly ash is consumed by cement manufacturers, balance of fly ash is stored without any means of disposal inside the plant. This research study discusses about development of fine aggregate replacement material using sintered coal fly ash with internal curing characteristics. A series of samples were prepared with various composition of fly ash and reservoir sediment material and sintered from 8000C to 13000C temperatures in the interval of 1000C for 30 minutes of sintering time the sintered fly ash was crushed to prepare fine aggregates. Reservoir sediment material was used as a binder material and it improved green strength of solidified fly ash. TGA – DSC and XRF analysis were used to investigate the thermal and chemical properties of raw materials, respectively. Microstructure of produced fly ash aggregate was observed using SEM photographs. Water absorption, water desorption and relative density of fine aggregate were measured. Water absorption and relative density of aggregates were in the range of 21 – 40%, 1.2 – 1.55, respectively. The aggregate with 80% of fly ash and 20% of reservoir sediment material which was heated at 11000C had 21.4% water absorption and 74.12% water desorption was selected as suitable replacement material instead of natural river sand. Relative density of selected fly ash aggregate was recorded as 1.46. Concrete was prepared using wetted fly ash aggregate by replacing 17.7% of natural river sand and the concrete was not subjected to external curing. Concrete with wetted fly ash aggregate gained lower strength at early stage then it gained more strength at 28 day than that of conventional concrete. Fly ash aggregate supplied internally stored water for hydration reaction of cement after finishing the free water presence inside the concrete and gave internal curing behavior to the concrete, therefore concrete with fly ash aggregate gained more strength than conventional concrete without external curing. Keywords - coal fly ash, reservoir sediment material, sintering, fine aggregate, water desorption, internal curing concrete.
item: Thesis-Full-text
Investigation on plastic waste utilization and management in fishery harbors of Sri Lanka
(2023) Muhandiram, PMSR; Halwatura, RU; Williams, KS; Liyanage, C
Fishery harbors (FH) are recognized as hot spots for coastal pollution as intensive anthropogenic activity takes place there. According to previous beach surveys conducted in the country, plastic was recognized as the major polluter. However, there are no studies being conducted which target plastic waste generation inside FH located in Western Province of Sri Lanka. The study was conducted from October 2022 to September 2023. For this study, weekly accumulation study method was followed along the land-water interface to collect primary data. Throughout the study period, a total of 34,188 anthropogenic debris pieces weighing 2650.47 kg were recorded from 59 data collection points within five FH. Plastic has become the major polluter both by count and by weight. By count it was 29,141 (85.24%) and by weight it was 1578.07 kg (59.53%). Therefore, plastics was recognized as the major polluter in FH located in the Western Province of Sri Lanka. By count only, rubber, metal, glass, processed wood and fabric represented 7.99%, 1.98%, 1.95%, 1.78% and 1.06% of the total anthropogenic debris respectively. The spatial variation in plastic debris accumulation was statistically significant in all five FH, while seasonal variation was statistically significant at Beruwala, South Dikkowita and Panadura FH. Plastic debris accumulation rates were 1.45, 2.21, 1.57, 0.98 and 0.17 items/m2/week for Beruwala, North Dikkowita, South Dikkowita, Panadura and Negombo FH respectively. The top ten debris, fishery industry related plastic debris, single use plastics and transboundary plastic products represented 84.64%, 10.71%, 60.94% and 0.27% of the total plastic debris collected from the five FH. Lower percentage of transboundary plastic products highlights that the problem is primarily a result of mismanagement of plastic waste within the harbor. There was a strong positive (r=0.883) correlation between number of plastic debris recorded and plastic weight. Correlation between monthly rainfall and monthly average number of plastic debris recorded had a very weak positive correlation for Beruwala, North and South Dikkowita FH whilst being negative for Panadura and Negombo FH. Correlation between the tide level and number of plastic debris recorded was weakly negative (r= -0.280). Stranding debris count was significantly higher than the floating debris at FH. Therefore, conducting cleanup projects at FH during low tide will be much more effective, with a priority on addressing stranding debris. A Stakeholder workshop and a questionnaire survey were conducted as a secondary data collection method. This was to reveal the perceptions and, attitudes of stakeholders as well as to find policy gaps related with plastic debris generation inside FH. Over half of the fishermen (51%) believe that the poor waste management of plastic within the FH by the Ceylon Fishery Harbors Corporation is the primary contributing factor for large amount of plastic waste generation. It highlighted the requirement of improving awareness among fishery communities, properly implementation of existing regulations and integrated stakeholders involvement. Key words: Fishery harbors, Plastic pollution, Coastal environment, Coastal contamination, Anthropogenic debris
item: Thesis-Full-text
Study of the behavior of multi-metallic systems under high-velocity impact loads
(2023) Wijekoon, KMSR; Fernando L
The behavior of multi-material layered systems under high-velocity impact loads, such as impact and blast scenarios, has gained significant attention from researchers over the past years due to its extensive applications in the automobile and aerospace industries, and ballistic armor and blast resilient structures. The focus is being shifted to multi-material systems over monolithic systems due to their superior characteristics in stress attenuation and energy absorption, and high preference for lightweight structures. In this research, an attempt has been made to investigate the impact-induced stress wave propagation through a multi-metallic layered system that is subjected to high-velocity impact loads. This study consists of two major components. 1) Elastic wave propagation and 2) Shock wave propagation. For the elastic wave propagation, four different test cases including a steel monolithic target, steel-titanium and steel-aluminium bi-metallic targets, and a steel-titanium-aluminium tri-metallic target, were considered. They were subjected to a low-velocity (180 ms-1) impact where only elastic waves are anticipated to be generated in the target. For shock wave propagation, only a steel monolithic target was considered which was subjected to an impact velocity of 350 ms-1. For both cases, numerical and analytical frameworks were developed to simulate the material response. The LS-DYNA finite element package was used to develop two-dimensional axisymmetric numerical models, and it was validated against the existing experimental results obtained from a single-stage gas gun test which were in good agreement. The analytical models which were the main focus of the present research were implemented in MATLAB which monitors and resolves the interaction of each propagation wave and then provides the overall response of the flyer-target system. The analytical model was validated against the results obtained from the validated numerical models considering stress-time histories. The outputs acquired from the analytical model for elastic wave propagation agree with that of the numerical model with reasonable accuracy. However, the developed analytical model for shock wave propagation gives reasonable results only up to the separation of the flyer and multi-material target where a significant variation can be identified between results after the separation. The developed models can be used to vi find the most optimum configuration in terms of stress attenuation for a given set of metallic materials which reduces the time and cost associated with high-velocity impact tests. Also, they can be used to find the required bonding strength to avoid debonding at material interfaces that cannot be obtained from experiments. Keywords: elastic waves, shock waves, multi-metallic, numerical modeling, wave interaction, analytical modeling
item: Thesis-Full-text
Optimizing mechanical properties of concrete using sugarcane bagasse ASH
(2023) Sankeeth, S; Lewangamage CS; Koswattage KR; Damruwan HGH; Herath S
In this study, sugarcane bagasse ash is recognized as a pozzolan, and the examination delves into its impact on the structural properties and durability of concrete. A signif icant volume of bagasse ash is generated annually in Sri Lanka through the recycling of raw bagasse for power generation in the sugar industry. The bagasse ash utilized in this study was procured from a local sugar factory in Sri Lanka. Diverse methods, such as X-ray diffraction, X-ray fluorescence, and laser particle size analysis, were utilized to evaluate the chemical, physical, and mineralogical characteristics of the bagasse ash. Additionally, a scanning electron microscope was utilized to examine the microstructure. The assessment extended to the examination of hardened properties such as compressive strength, bond strength, tensile strength, ultrasonic pulse velocity, and durability properties including water absorption and penetration of chloride. The concrete mixtures were formulated by substituting bagasse ash at ratios rang ing from 5% to 20% by weight instead of Portland cement. The local ash demonstrated pozzolanic characteristics as per the results of chemical, physical, and mineral tests. Notably, mixtures containing 5% to 15% bagasse ash substitution were identified as optimum replacements for achieving elevated compressive and tensile strength. Si multaneously, the water absorption and rapid chloride permeability test indicated a lower value of up to a 10% ash content percentage than control concrete.
item: Thesis-Abstract
Feasibility of using lightweight load-bearing panel systems in duplex apartments of tall buildings
(2023) Mahaarachchi, TN; Jayasinghe MTR
As an inevitable result of the growing population in recent times, requirements for housing facilities, land scarcity, and overexploitation of natural resources have created many problems, both environmental and social. Due to the shortage of land in cities, land prices have increased rapidly in recent times. One solution for the lack of land is to have multi-storey apartment buildings, though the land prices can be distributed among many owners. Because of that, over the last few decades, the number of tall buildings has seen an exponential increase. Moreover, because of the urbanization of cities, more people tend to live in apartment buildings than in small housing units. Along with that, the time taken for the construction and the cost can be identified as significant issues in construction. To overcome these problems, lightweight EPS panels can be considered a proper alternative. This research is mainly focused on assessing the structural feasibility of a duplex apartment with tall buildings. This can have a significant cost benefit since the strong post-tensioned concrete floor is needed only once on two floors. To achieve that, load-bearing partitions should be lightweight. The lightweight NERD slab system is used in the duplex apartment intermediate floor due to its low cost and light weight. To assess the structural feasibility, an idealized finite element model was done using the MIDAS GEN commercial package. The conventional type of tall building is modelled using the same software and compared with the duplex model. In high-rise buildings, providing car parking within apartment buildings often leads to a situation where different grid arrangements exist on the parking and apartment floors. Another grid arrangement for a tall building requires a transfer system, such as a transfer plate or transfer beams. This study explores the transfer plate effect due to the duplex house’s architectural form. The feasibility study was carried out with a fifty-seven storey building as a case study. The results obtained from the two analytical models were used to check the structural feasibility of lightweight EPS panels as a load-bearing panel system in duplex apartments. Keywords: EPS light-weight wall panels, duplex apartments, tall buildings
item: Thesis-Full-text
Investigating community resilience to climate change : application of economic models
(2023) Nadeetharu, BKM; Kulatunga U
Climate change is a significant issue in the present which impacts the economic status of communities by affecting their livelihoods. To investigate the problems of climate change on communities, economic models of climate change can be regarded as a suitable application, as they provide the parameters and climatic conditions to be considered. Thus, this study aimed to contribute to enhancing the community's resilience to the economic impacts of climate change in Sri Lanka through the application of economic models. Five climatic conditions, seven firsthand influences of climate change, and 25 parameters under four categories to determine economic impacts have been identified through a systematic literature review. This research adopts interpretivism philosophy and pace through a qualitative research approach to derive an abductive conclusion. Data collection has been conducted in four stages; preliminary interviews, focus group discussions, key informant interviews and expert interviews respectively. Stages 01 and 04 of data collection followed the survey strategy while Stages 02 and 03 aligned with case studies within low country wet zone tea and paddy industries. The findings were analysed using content analysis, and cross-case analysis. Finally, two causal loop diagrams (CLDs) have been developed for two cases. The findings revealed temperature and rainfall as the two main climatic conditions varying in Sri Lanka, while low country wet zone mainly suffers from rainfall variations. Despite the benefit of lowering the irrigation cost, climate change poses common and unique challenges for both tea and paddy growers. Six and four strategies for building resilience have been identified for tea and paddy growers respectively. Seven and six closed loops have been identified within the CLDs for tea and paddy respectively. The findings provide an influential understanding for decision makers to derive policies and the developed CLDs can be benchmarked in system dynamic models. Keywords: Climate change, Economic impacts, Livelihoods, Causal loop diagrams (CLDs), Systematic Literature Review (SLR)
item: Thesis-Full-text
Evaluation of effect of tree roots on shear strength of soil due to root water uptake
(2023) Kaushalya AAS; Pallewattha MA; Nawagamuwa UP
Tree roots play a major role in ground and slope stabilization by increasing the strength and stiffness of the soil positively. When evaluating how vegetation affects ground improvement, tree roots are the primary factor because that they improve the strength of the soil with the help of their mechanical properties and provide the additional soil suction by the root water uptake. Previous studies, however, focused on the mechanical and hydraulic impacts of tree roots separately when evaluating the impact of vegetation, which failed to yield reliable results because suction influences on mechanical characteristics of tree roots. Recent laboratory research has shown that the mechanical interactions between roots and soil, such as root tensile strength and root cohesiveness, are suction-dependent. There are still significant gaps in knowledge regarding the effects of suction and root concentrations on root reinforcement despite these extensive previous research. This study investigated the influence of matric suction on root reinforcement of the Alstonia macrophylla with Sri Lankan Silty Sand using large-scaled direct shear tests. Cohesion due to root reinforcement of the Alstonia macrophylla should theoretically equal to the difference between the apparent cohesion of reinforced and unreinforced shear strength in saturated samples. This value was 2.99 kN/m2 when RAR, dry biomass of roots per unit volume of soil, and total leaf area of the plant were 6.22 x 10-3 %, 0.575 kg/m3 and 1195 cm2 respectively. However, the cohesion due to root reinforcement of the Alstonia macrophylla is slightly increased with the matric suction in the Sri Lankan Silty Sand as per the research outcomes
item: Thesis-Full-text
Investigation of ground vibrations due to moving trains
(2023) Thadsanamoorthy P; Damruwan HGH; Lewangamage CS
This research focuses on the assessment of train-induced ground vibrations through experimental analysis and the development of a Finite Element (FE) prediction model. The study aims to evaluate the intensity of vibrations caused by trains and understand their effects on different soil types and train speeds. A vibration sensing device named "VIBSEN" was developed for the measurement of ground vibrations. Experimental data were collected at 3m intervals from the centreline of the railway track and processed using MATLAB software. The accuracy of the device was confirmed through gravity calibration and comparison with a vibrometer. Based on the experimental study conducted at a specific site, it was determined that the minimum safe distance from the centreline of the track is approximately I Om when two trains cross simultaneously and approximately 6m when considering the passage of a single train. It should be noted that these recommendations are specific to the soil profile at the experimental site and may vary depending on subgrade soil type and parameters. The FE prediction model, developed using MIDAS GTS NX FE software, was validated using experimental results from the study and further compared with literature data. The model successfully predicted train-induced ground vibrations, demonstrating its applicability. Parametric analysis was conducted to investigate the effects of soil type and train speed on vibration intensity, including the identification of resonance frequencies and critical velocities. The findings of the study indicate that vibration intensity varies significantly depending on the soil type, with lower intensities observed for soils with higher elastic moduli. Additionally, the study highlighted that vibration intensity increases with train speed, and certain speed levels may lead to a sudden increase in intensity due to resonance effects. The resonance frequency was found to be influenced by the elastic modulus of the subgrade soil. Overall, this study provides valuable insights into train-induced ground vibrations and offers recommendations for safe distances from the track centreline. The developed VIBSEN device and FE prediction model offers reliable tools for future investigations and allow for parametric studies considering different soil properties, train loads, and speeds. These findings contribute to mitigating risks, minimizing structural failures, and reducing hazards associated with prolonged exposure to vibrations.
item: Thesis-Full-text
Homogenized response of ultra-thin woven fibre composites under flexural loading
(2023) Gowrikanthan N; Mallikarachchi HMYC; Herath HMST
Design of large space structures is restricted due to the limited storage capacity of launch vehicles. Deployable structures made with ultra-thin woven fibre composites eliminates this bottleneck due to self-deploying nature. These structures can selfdeploy using the strain energy stored during elastic folding. Popularity of selfdeployable structures got increased due to their high strength, lightweight, and good packaging properties. However, thin woven fibre composites undergo large deformation during folding process due to the formation of high curvature, which causes reduction in bending stiffness. Hence, it is crucial to understand the mechanical behaviour of these structures before implementing, in order to avoid unnecessary failures. Numerical modelling techniques have become popular in this research area due to the advancement of computational methods to obtain the mechanical properties of thin woven fibre composites. Homogenised Kirchhoff plate-based representative unit cell modelling technique with solid elements is considered in this research. Corresponding ABD stiffness matrices are obtained with using virtual work principle, where the repetitive nature of woven fibre composites is represented by periodic boundary conditions. First, a series of micro-mechanical analyses is carried out to observe the influence of the relative positioning of tows on the mechanical properties of thin woven fibre composites. Various phase shifts between the plies have been considered in this research which might be originated from the inter-ply misalignment during the manufacturing stage. The outcomes of this parametric study clearly depict the variation in in-plane and out-of-plane properties extracted from the ABD stiffness matrices and describe the potential causes for the detected deviations between experimental and numerical results. Next, a resin embedded unit cell model is developed to predict the non-linear bending behaviour with degree of deformation. Initially, a geometrically linear analysis is carried out and then the analysis is extended to non-linear region to observe the moment-curvature response. Linear analysis results of extensional stiffness and Poisson’s ratio showed good agreement with the experimental results extracted from the literature. However, the out-of-plane properties and shear stiffness values were overpredicted. Similarly, non-linear analysis overpredicted the bending stiffness throughout the considered curvature range. Hence, the resin embedded unit cell model needs further improvements and modifications to accurately predict the out-of-plane properties, and capture the reduction in bending stiffness.
item: Thesis-Abstract
Experimental analysis on the workmanship factors and performance of fibre optic infrastructure monitoring cables embedded in concrete structures
(2023) Gowshikan A; Ranasinghe KAMK; Danushka KKGK.; Xu X
Structural health monitoring helps to protect infrastructure by guiding timely interventions. Distributed Fibre Optic Sensing (DFOS) is one such monitoring technique with significant advantages such as continuous measurement capability, small size and lightweight. This is the first time introducing the Fibre Optic Monitoring technology to Sri Lanka. A recently developed FOS technique, Brillouin Optical Frequency Domain Analysis (BOFDA), provides advantages such as smaller sized analyser unit and faster measurements, however, it lacks experimental evidence on the measurement accuracy. FOS, in general, also has unestablished workmanship practices on pre-straining and placing of fibre optic cables. This study is particularly aimed at BOFDA-based instrument calibration and verification of the accuracy of the BOFDA-based strain and temperature measurements. Firstly, laboratory experiments were performed to investigate the accuracy the measurements provided by the BOFDA-based DFOS system using the strain cable calibration test setup and temperature cable calibration test setup. These calibration tests indicated that actual maximum spatial resolution of the selected BOFDA unit is in the range of 0.4 - 0.6 m. The strain and temperature measurements provided by BOFDA were found to be reliable, since constant strain and temperature coefficients were observed. The workmanship practices were examined using a set of four-point beam bending tests with different configurations of FO cable locations and pre-tensioning levels. The results showcases that the location of the fibre cables, whether on the surface or embedded in concrete either near or away from the reinforcement, had no significant effect on the accuracy of strain measurements. However, contrarily to the practice, clear evidence was found on the need for pre-straining of strain cables to obtain accurate compressive strain measurements. This research therefore showcases the reliability of BOFDA technique and encourage future fibre optic monitoring deployments to ensure pre-straining of fibre optic cables as a good workmanship practice.
item: Thesis-Full-text
Seismic vulnerability assessment of masonry infilled reinforced concrete school building frames in Sri Lanka
(2022) Sathurshan, M; Mallikarachchi, HMYC; Thamboo, JA; Wijesundara, KK
Sri Lanka is considered as an aseismic country, hence the seismic risk is not explicitly considered in the planning and designing of critical structures. However, current studies indicate that the seismic risk cannot be completely omitted when designing buildings in Sri Lanka, particularly post-disaster structures like schools and hospitals that should be designed to withstand any potential seismic action. Meanwhile, assessing the seismic risk of all the critical structures in depth across Sri Lanka might not be an easy task, and therefore, the creation of a rapid assessment method would help to effectively screen the buildings which are seismically vulnerable. Therefore, in this study, an attempt was made to assess the seismic vulnerability of school buildings in Sri Lanka in detail by incorporating possible variations and proposing an alternate Rapid Visual Screening method (RVS) for Sri Lankan conditions by incorporating FEMA P-154 guidance. In order to study the existing school building typologies, detailed structural surveys were carried out across Sri Lanka in selected school buildings. The survey revealed that school buildings in Sri Lanka can be characterised as reinforced concrete (RC) frames, infilled with unreinforced masonry walls (MI). Based on the structural configurations, mainly two building typologies were found as (1) Type 01 and (2) Type 02. Nonetheless, in terms of MI arrangements, it was observed that significant variations exist among the school buildings. Therefore, those variabilities were explicitly taken to assess the seismic performance of MI-RC school buildings. The seismic performance of the school buildings was analysed using the OpenSees (OS) finite element programme. The torsional effects and post-processing as shear capacity and stochastic material properties (concrete, steel, and masonry) from Monte-Carlo simulation were incorporated in this study. The modal analysis and non-linear static pushover analysis were carried out, in which a total of 640 building cases were analysed. The analyses of pushover (PO) and seismic fragility revealed that the Type 02 buildings exhibit significantly better performance than the Type 01 buildings. Also, the variation in MI arrangements significantly influences the seismic resistance of the buildings. In addition, the application of the proposed RVS method is effective to carry out the seismic screening method of school buildings in Sri Lanka. Keywords: School buildings, Non-linear static pushover, Seismic performance assessment, Seismic Fragility assessment and Rapid visual screening method
item: Thesis-Abstract
Designing and developing a prototype of smart and hybrid paving system
(2022) Kumarage NR; Jayasinghe C; Perera KPH
Landfilling has now become a prime concern all around the world, not only because it squanders usable land, it causes major environmental issues such as contamination of soil, water, and air, as well as an impact on human health. Glass is one of these waste products which is often dumped when mixed with impurities. A similar landfill was found in a Sri Lankan glass factory dumping its waste for over 20 years. Moreover, one of the major drawbacks of Permeable Interlocking Concrete Paving (PICP) is its unsatisfying appearance. Although many researchers created better aesthetic appearances for PICP, none were cost-effective. Hence, a study was implemented to solve these two issues by developing sustainable paving blocks with smart top-layer customizations utilizing this glass waste. Initially, finite element modelling was used to determine the optimal paving block dimensions, and 200x100x80 mm 3 was discovered to be the ideal paving block dimension for cobble-type paving blocks. Following that, tests were performed on glass waste to determine its suitability for use as fine aggregate. In all tests, glass waste exhibited favourable results. As a result, a mix design was developed using this glass waste, and it was discovered that it could replace 100% of the fine aggregate while maintaining structural strength. Three alternatives were proposed to meet the customers' aesthetic satisfaction and were tested in accordance with the SLS 1425 standard, in which all three alternatives resulted satisfactorily. Finally, a Life Cycle Costing Assessment (LCCA) was performed to determine the economic feasibility of the proposed products. LCCA indicated that when only mortar is considered, the proposed mix has a 37% cost reduction, and after smart top layer customizations, two alternatives had 6% and 5% cost reductions, while the final alternative had a 17% cost increment compared to existing paving blocks.
item: Thesis-Abstract
Case based analysis on potential benefits of changing Sri Lankan office buildings towards green rated building designs
(2022) Ariyarathna RIS; Halwathura RU; Danilina N
Office buildings are one of the main categories of buildings which possess a rapid growth rate in the context of urbanization. They contribute to a major part of energy consumption in commercial building sector. Even though, the need of adopting energyefficient features arises, the higher initial construction cost and the myth of longer payback period have been made barriers to this movement. Hence, this study focuses on identifying possible energy-efficient strategies, and their economic performance during the life cycle of the building, to perform an Life Cycle Cost (LCC) to compare the total costs incurred in the conventional office building and a green building and to select the best design that ensures the lowest overall cost with high-quality functions. This study consists of 10 randomly selected low-rise office buildings located in the commercial capital of Sri Lanka, Colombo. Followed by the preliminary survey conducted, it was recognized that high initial cost and the longer payback period was the main two hurdles for the office building owners to move towards the energyefficient buildings. A conventional office building possesses a 140,000200,000LKR/m 2 of LCC, and a Building Energy Index (BEI) of around 250 kWh/m . Thereafter, based on a defined energy efficient strategy these buildings were developed as energy efficient buildings in 4 stages. Accordingly, it was concluded that stage 4 platinum level energy efficient building is the best design for a low life cycle cost, and it results in a payback period of 3-4 years, 20%-30% of increment in initial construction cost, 30%-40% increment of maintenance cost and 20%-25% reduction of building LCC compared to the conventional office building design.
item: Thesis-Full-text
Field evaluation of thin asphalt application in low volume roads in Sri Lanka
(2022) Dishan M; Mampearachchi WK
Thin Asphalt surfacing (TAS) is an innovative idea that has the potential to lower construction and maintenance costs of road construction in Sri Lanka. Laboratory based studies conducted in Sri Lanka have shown that the local materials can be used to produce TAS, and this study focuses on the usability of TAS in the field. Few concerns were found when applying this new technology in the field was taken into consideration before field trial. Such as: (1) The possibility that variations in the gradation of aggregates within the specification limit could negatively affect the characteristics of asphalt mix. Investigations were conducted to look at the impact of coarser and finer gradations on Marshall Properties: these grades represent the upper and lower limits of the proposed specification range, where both mixtures fulfilled the requirements. (2) The impact of the top level of longitudinal profile tolerance on the actual thickness of the asphalt mat. Increase in the proposed layer thickness from 25 mm to 30 mm, and adding additional surface top level correction of the base layer to meet the top level of longitudinal profile tolerance of ±10 mm are the options that have been suggested to meet the specified thickness conditions for TAS, where it was found that both approaches can be advantageous. (3) The rate at which heat is released by an asphalt layer that is thinner than traditional asphalt layer. The results of the laboratory-based testing show that paving around 8 a.m. leaves the least amount of time for compaction. This occurred because the temperature of the ground and the surrounding air was low . Findings on the time for compaction in the morning and evening are quite comparable. This similarity shows that base temperature is more significantly impacted by solar flux than the mix temperature. After the conclusion of surveys and laboratory experiments, it was decided to trial TAS in a road in the Gampaha district with low volume traffic. Construction was done in two sections. Section 1 was constructed with a 30 mm thickness and Section 2 with a 25 mm thickness. Under the test section's field conditions, the results for 30 mm layer thickness were significantly better. The temperature reduction of the asphalt layer surface over time was observed during the trial and the time available for compaction was less than 20 minutes. Through this study it was verified that TAS mixtures within the proposed aggregate gradation limit, satisfy specification requirement, top level surface tolerance of the base layer should be adjusted to ±10 mm, it is advantageous to have 30 mm thick TAS layer rather than 25 mm TAS layer considering the fluctuations of surface level of base layer and sunny noon time is more favourable to lay TAS considering the time available for compaction. It was identified that 30 mm thick TAS sections is more attainable than 25 mm thick TAS section during field applications
item: Thesis-Full-text
Characterising mechanics of deployable coilable tape-springs
(2022) Sutharsanan N; Mallikarachchi HMYC
Deployable structures play a vital role in a variety of applications such as aerospace structures, rapid development civil engineering projects, medical devices, reconfigurable robotics and many other engineering applications. Deployable thinwalled booms make use of elastic strain energy during storage and are capable of selfdeploying to their fully deployed configuration which is an ideal candidate to overcome the bottleneck of limited launch vehicle capacity faced in space applications. In this research, an attempt has been made to characterise the mechanics of tape spring booms which are the simplest form among the coilable booms. Numerical and analytical frameworks are established to investigate the large deformation analysis of deployable coilable tape springs during the flattening process, which is the initial process of coiling. Geometrically non-linear finite element models implemented in Abaqus/Standard are used to characterize the flattening mechanics of isotropic tape springs under compressive deformation. The effects of geometric and material properties on flattening behaviour are investigated through a numerical parametric study. A simple analytical model is developed to predict the stresses and forces during compression flattening, and a good correlation has been found with the numerical study. The tension stabilized coiling behaviour of longer tape booms is then investigated through analytical and numerical studies. A useful analytical model is developed to determine the required minimum tension force to prevent instabilities such as blossoming instability and buckling instability. The influence of varying coiling radius due to the thickness of multiple turns is taken into account in the developed analytical framework. Also, the required minimum torque and power for tension stabilized coiling of tape spring are developed considering energy conservation where the effect of friction is also considered. Coiling of isotropic tape spring booms is simulated in commercially available finite element software Abaqus/Explicit. A good correlation has been found between the numerical and analytical results in terms of the required torque for coiling of longer tape-spring. Furthermore, a novel approach to predict the minimum required tension force to prevent the instabilities is proposed. A numerical parametric study is conducted utilizing this technique in order to study the effect of the coiling ratio on the required tension force. In terms of the bending and tension-dominated regimes, the numerical findings exhibit good qualitative agreement with the established analytical model. Furthermore, a linear trend is observed in the numerical results for the loss of uniqueness region, which is helpful for the development of analytical models.
item: Thesis-Full-text
Applicability of neural network models for real-time flood forecasting in dry zone and wet zone river basins, Sri Lanka
(2022) Subramaniyam C; Rajapakse RLHL
Flood forecasting is a powerful tool for flood management and early warning, where the anticipated flow values are determined by incorporating basin attributes and climatic factors. In the field, data-driven models offer beneficial solutions compared to comprehensive physical and statistical tools; neural networks have evolved to perform flood forecasting without understanding the physical mechanism. However, forecasting efficiency and reliability are insufficient due to the augmentation of predictive span and improper data handling strategies. In addition, the poor interconnectivity of spatial-temporal resolution influences the accuracy of flood forecasting in a dry zone. Thus, the present study aimed to enhance the flood forecasting ability of neural network models for a 30-day horizon by learning the daily input series of climatic and physiographic factors of the catchment region. Further, the data manipulation strategies were adapted to enhance the learning capabilities. In addition, pretrained models were developed based on the model performance in the wet zone basin to enhance the predictive quality in the dry zone basin. The NN models were developed for the Kelani River flood forecasting, where significant flood events have frequently destroyed the socio-economic features of the basin. Besides, pretrained models were tested on the Maduru Basin flood events, which have encountered inundation due to prolonged flood peaks. Thus, climatic and physiographic data were gathered for both basins and improved with hydrological and data science-based data manipulation strategies. On the other hand, the Box-Cox transformation was employed to redistribute the input series into a Gaussian state to enhance the learning ability of NN models. Consecutive windows were proposed to consider 30-day daily input to forecast the next 30day streamflow values while sampling. Thirteen (13) NN models were compiled, fitted, and tested on the Kelani Basin. In addition, grid analysis was adapted to rank the performance of models based on statistical tools, where bidirectional models explicated excellent quality in flood forecasting. Besides, uncertainty analysis was proposed to investigate the impacts of data handling and input combination on flood forecasting. Two hybrid models significantly expounded underperformance without box-cox transformation; none of the models illustrated excellent performance without box-cox transformation. Moreover, scaling/normalization severely influenced the model performance considerably for hybrid models. Besides, sensitivity analysis was applied to verify the applicability of model architecture on model performance. Unlike the types of optimizers, other sensitivity parameters revealed inconclusive results for model performance. None of the modified models delivered more excellent performance than the core models. Further, Bidirectional Gated Recurrent Unit (BiGRU), Bidirectional Long- and Short-Term Model (Bi-LSTM), and Attention Based BiLSTM (Att-BiLSTM) expressed 0.98, 0.95, and 0.97 for the wet zone flood forecasting, respectively, which were chosen as pre-trained models delivered a similar performance for the dry basin. In future studies, the consecutive data batches must be determined according to the guiding parameters, such as global warming and climate change. Besides, the loss function should be replaced with other statistical terms to incorporate an optimizer, and autocorrelation must be adapted to control the error propagation. In addition, the core model must be trained for extended periods to effectively perform transfer learning on other basins.
item: Thesis-Full-text
Building material selection framework for Tropical climatic conditions : an eco-design based approach
(2022) Gurupatham SV; Jayasinghe C; Perera KPH; Raju L
All over the world, sustainability has been given immense attention, thus novel stateof-the-art materials and building systems are emerging as alternatives. With those different alternatives, comparison and the selection of a better-performing material or a building system using diverse perspectives such as economic, ecological, social, and cultural are important to ensure the adaptation of the proposed research findings to the particular community. Even though many researchers introduced multiple material selection frameworks using economic and ecological parameters, a holistic approach including Social and Cultural adaptability of those selections has been overlooked in previous studies. This study proposed an eco-design-based material selection approach that considers the individual and wholistic perspective of diverse themes including economic, ecological, social, and cultural. Several sub-themes are identified under each theme and are verified through expert surveys. The pairwise comparison of themes and subthemes and analysis using the Analytical Hierarchy Process (AHP) leads to proposing weights for each theme and sub-theme and developing an eco-design-based material selection framework in ranking and choosing better-performing building materials. Accordingly, saving energy, reducing the overexploitation of natural resources, reducing energy emissions, and reducing construction, as well as operational cost, are the parameters that create a greater impact on the selection of sustainable material with the aid of eco-design. Furthermore, the developed framework is validated by comparing an emerging walling material Cement Stabilized Earth Blocks (CSEB) with conventional materials such as Burnt Clay Bricks (BCB) and Cement Sand Blocks (CSB). Technique for Order Preference by Similarities to Ideal Solution (TOPSIS) had been carried out to compare and rank the respective walling materials under different scenarios. Accordingly, CSEB is concluded to be the best alternative when analyzed in the eco-design concept. Furthermore, individual analysis of ecological and economic themes shows that CSEB is the best material over the long run while BCB is said to be performing well socially and culturally. The proposed framework could be highly beneficial for industry practitioners such as contractors, building developers, planners, and policymakers in choosing communitypreferred, affordable, and environmental-friendly construction materials. Moreover, this piece of research could be improved with the inclusion of fuzzy numbers which enables consideration of uncertainty.
item: Thesis-Abstract
Development of an insulation plaster for fiber reinforced polymer (FRP) concrete composites using cementitious material
(2021) Kajanan S; Gamage JCPH
The energy used to maintain the thermal comfort of building greatly contributes the greenhouse gas (GHG) emissions and global warming. This study developed a sustainable cost-effective rice husk ash (RHA) based mortar for the wall plaster to improve the thermal insulation, reduce the operational energy and enable the thermal comfort. RHA was partially replaced the sand in the conventional mortar to produce the RHA based plaster. Compressive strength and thermal conductivity tests were conducted, and the results highlight that the RHA can be replaced up to 30% of sand in the conventional mortar to produce a wall plaster with improved thermal insulation with adequate compressive strength. Further, this study investigates the thermal performance of the RHA-based plaster through measured the heat transfer rate under full open weather conditions. Two identical prototype model houses were constructed with RHA-based plaster and conventional plaster, and internal and external wall surface temperatures were measured for 3-days cycles. The results highlighted that on average peak heat flux reduction formed by the RHA-based plaster mortar was 10%. The average daily heat transfer reduction across the wall with RHA-based plaster was 26%. Further, results show that RHA-based plaster can reduce the energy that required to enable the thermal comfort by about 9% than the conventional mortar. The environmental impact analysis was also conducted to assess the sustainable performance of RHA-based mortar. The assessment highlights that RHA-based mortar has less environmental impact than the conventional mortar. Further, the CO2 emission produced by the production of RHA-based mortar is about 14% less than that of from conventional mortar. At last stage the developed plaster was applied with CFRP specimens and checked for the thermal test and bond test using single shear test. 70% to 73% fire resistance can be achieved respect to the commercially available material (Vermiculite-cement).