Master of Science By Research

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

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item: Thesis-Full-text
Accident analysis beyond descriptive statistics
Devasurendra, KW; Bandara, S
Worldwide, more than 1.2 million people die annually from road accidents and now it is the 8th leading cause of death in the world. In the context of Sri Lanka, road traffic injury is also a leading cause of mortality and morbidity. In year 2014, 35,967 crashes were reported where 6% of them are fatal contributing to 2,440 deaths. Providing effective countermeasures for the identified safety issues and proper policy developments are vital in mitigating the issue of road traffic accidents. Under this study, a comprehensive analysis of road traffic crashes of the country in terms of descriptive statistics was carried out using ‘Sri Lanka Police Accident Database’ to find the road safety condition of the country with the objective of providing a basis to encourage concentrated and in depth studies in road safety of the country. Over the decade 2005 – 2014, on an average, 6 people have died every day in Sri Lanka form road traffic crashes. According to the accident details of the last five years, age group 15-29 accounted for 33% of the total casualties in the country and 23% of the total fatalities due to road crashes. Pedestrians accounted for 21% of those who died from 3W related crashes. Promotion of public transport, strict law enforcement on helmet usage, design change of three-wheelers to limit sharp turns and more road safety education are among the suggestions made that can improve the road safety condition. However, only with descriptive statistics it is not possible to carry out an in depth review of the causes of accidents. Therefore, statistical methodologies have been improving which have enabled better safety design and policy improvements. In this study, a stepwise binary logistic regression was used for heavy vehicle related crashes to show the importance of accident analysis. Among the identified contributory factors, heavy vehicle crashes occurring during 03:00 – 06:00 hours, occurring at Batticalo, Chilaw and Jaffna DS Divisions and crashes involving intercity busses, semi government heavy vehicles are some of the factors that have a higher chance of becoming a fatal crash.
item: Thesis-Full-text
Analysis of disaster management frameworks to evaluate the hazard induced risks of coastal communities
(2020) Rathnayake WKD; Siriwardana CSA; Dissanayake PBR; Bandara CS
Natural hazards were recognized globally as the most pressing risk in terms of impact and probability of occurrence. This context presses the need for strong, effective risk management mechanisms in the field of disaster management. Yet the ever increasing casualties, economic losses due to natural hazards raise the question on the effectiveness of respective mechanisms to mitigate such. That leads to the objective of this research work, to find engineered solutions for the disaster risk management mechanism to be more effective. The research work conducted in three phases. First a literature survey to identify the risk management principles, disaster management principles, and disaster and risk relativity and evaluation methods. The next phase is framework development. Number of frameworks were developed as part of the research work to evaluate the effectiveness of a disaster management mechanism and to capture the details of a given mechanism. Third phase is the three case studies in three countries, Sri Lanka, Myanmar and Maldives. Collected data were then analyzed to capture an ideal disaster management mechanism. It was identified that there are number of factors can include in to a disaster management mechanism from a risk management perspective. Also it was identified that the developed frameworks do capture the details of a disaster management mechanism in a satisfactory way. There are number of practices countries can share within to enhance the mechanisms. Also the research work concluded with an institutional ideal arrangement in a disaster risk management perspective.
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-Abstract
Application of geographic information system for land clearances in the city of Colombo Sri Lanka
(11/30/2011) Leelananda, HH; Wijesekera, NTS; Peiris, TA
The study aims to improve land clearance processes in Urban Development Authority (UDA) with the support of Geographic Information Systems. The objective is realized through the conduct of geographical analysis, query, and modeling. The study takes Thimbirigasyaya Ward in the City of Colombo as a case for developing the land clearance system. UDA is the main Government Agency dealing with physical planning in Sri Lanka. The primary activity of the UDA is the preparation, implementation, and maintaining of National Physical Plans, Regional Structure Plans, and Local Development Plan within its declared areas. A study is done to understand the context of land clearance processes in UDA and to develop a digital system for land clearances. The study takes a critical look at how UDA practices land clearances and monitoring, and applies information technology tools to support such functions. It reviews UDA regulations and identifies issues in land clearances and database management. The method that has been exercised in developing a Land Information System (LIS) is basically in three forms. They are (1) Identifications of shortcomings in the present system. (2) Identifications of targets. (3) Finding ways in reaching the targets. Collection of data is first subjected to detailed study in order to find its accuracy and a database has been to developed using data layers and attributes by converting analog maps and statistical data into digital form. Then land information were tested and verified for its accuracy. Selection of the study area was done through a suitability analysis and availability of updated data. A model was then developed using GIS tools, its data accuracy was checked and found that the results had been in proper order. The developed LIS was compared with the existing processing system and was proved effective. The accuracy of the data is very important in the process of developing a good LIS. In this study checks were carried out to ensure data accuracy. Numerical checks including stepwise calculations and field measurements were done to verify the model. The system developed using GIS has a significant advantage over the existing system. Clear improvements were visible in the area of labour and time saving and also in the provision of alternative solutions. System output identified the present distribution and use of land parcels. This gives rise to the need of establishing norms for rational decision making. UDA is basically benefited by this system on followings. (1) Serve as platform to integrate data and facilitate data exchange, (2) provide immediate access to data, (3) spatial analysis for selection of alternative sites, and (4) easy decision-making.
item: Thesis-Full-text
Application of mathamatical modelling in investigating coastal phenomena
(12/2/2011) Wijesekara, GN; Hettiarachchi, SSL; Samarawickrama, S
With the evolvement of Information Technology, the simulation of physical theories on real matter in order to envisage the behavior of man-made structures and its impact on earth resources have “spread its wings” from scaled models to highly sophisticated virtual reality computer models where all elements can be viewed in 2D/3D in graphic user interfaces. Particularly the study in Coastal wave mechanics and simulation of such uncertainty with man-made structures, have proven the value of technology and it has been much effective with cost and time. With the current research that had been carried so far, commercially used in-house wave models were studied and a whole new design and analysis of a computer simulated numerical model for Sediment Transport Modelling was carried out. Case study on Hambanthota describes the coastal processes that has been undertaken in order to investigate the wave climate, wave induced currents and sediment movement for the proposed fishery harbour at Hambathota in Sri Lanka. Various components of an available wave modelling suite (“Halcrow”) were applied to evaluate the nearshore wave climate for design purposes, for optimization of the harbour configuration, for examination of wave penetration and for the input to the beach evolution model. The wave modelling shows that there is no significance wave penetration for the proposed fishery harbour. In addition, Wave-induced current modelling and investigation of beach evolution of the existing bay has been undertaken. The proceedings of a final year project discussed on environmental impact on ecological and social environment with several proposed alternatives for a fishery harbour in Negombo Lagoon were considered for a case study using a commercial wave model to examine the significance impact of the wave climate for the nearshore region and structures proposed to be located in Negombo Bay. Several components of “Halcrow” wave model are used in order to validate the first alternative and modifications required are suggested herewith. Most important of all, a sophisticated numerical model is designed and analyzed with the use of paradigms of software engineering for the simulation of Alongshore Abstract Sediment Transport. Equations by Kamphuis (1992) based on empirical co-relations and dimensional analysis of properties have been used and followed through the whole design. Theories and equations integrated from research carried out by Dr. Saman Samarawickrama were used in deriving solutions for the numerical model of which the design is based on many GIS (Geographical Information System) functionalities.
item: Thesis-Full-text
Auto-tuning multi-tiered application for performance
Fernando, V; Jayasena, S
Auto-Tuning Multi Tiered Applications for Performance With the widespread use of cluster-based environments, getting the maximum possible performance from multi-tiered web applications becomes an important task. The large numbers of configurable parameters in such environments and applications, however, makes manual performance tuning (i.e., searching for and identifying key parameters that affect performance and optimal values for those parameters) extremely difficult, if not virtually impossible. The problem becomes further complicated because the key parameters and/or their optimal values will vary across environments, applications and workloads. In this work, we explore the autotuning approach, which is generally used to automatically tune the performance of programs in traditional HPC settings, to tune multi-tiered web applications. Our approach is based on OpenTuner, a framework used to build auto-tuners to search through a configuration space for an optimal configuration. Even for this autotuning approach, the wide variations and the dynamic nature in the runtime environment, such as network congestion, variations in demand, possible node failures and changes in workloads pose a significant challenge. In this work, we explore offline and online tuning techniques to overcome the challenges of autotuning multi-tiered applications. We present results of offline autotuning experiments that tuned benchmark applications for multiple performance goals. We show that 20% - 25% improvements in response time and throughput can be achieved through our offline autotuning approach. We present a way of reducing the tuning time by pruning the configuration space. We identify the parameters in web servers that contribute most to performance. We also show that different performance goals can lead to differences in configurations and discuss the shortcomings of offline autotuning methods. We also take a look at online tuning methods and show that online tuning of multi-tiered applications is feasible.
item: Thesis-Full-text
Bond performance of CFRP/Steel composite at elevated temperatures
(2019) Chandrathilaka ERK; Gamage JCPH
Carbon Fibre Reinforced Polymer (CFRP) is being used as a retrofitting material for different structures such as, concrete and steel. Glass transition temperature (Tg) of the bond between CFRP and steel influences on the service and fire performance of strengthened members. A total of eighty-two CFRP/steel double strap joints were prepared and tested under elevated temperature. They were cured under a range of elevated temperature conditions in the control laboratory environment and in the open environment which is practically feasible in large civil engineering structures. The test results showed a similar trend of reductions in the bond strength, Poisson’s ratio and Elastic modulus of CFRP/steel joint with the exposure to the elevated temperature. More than 50% reduction in the Poisson’s ratio, elastic modulus and the bond strength was noted when the bond line temperature exceeds Tg + 15 0C, irrespective of the curing time and curing conditions. Initial elevated temperature curing also causes for shifting the curves in the right-skewed direction. A significant increase in Tg of bond was noted with 4 hours initial curing at 75 0C, i.e. Tg +20 0C. Then a numerical model develops to predict the bond characteristics of CFRP/steel composites cured under different curing conditions and their behaviour at elevated temperatures. The measured material properties and their degradation with the temperature exposure were considered. The predicted bond performance was in a good agreement with the test results. The strain variation in the CFRP sheet was used to develop the bond shear stress-slip variations. Parametric studies were also conducted to evaluate the effects of bond line parameters on the bond shear stressslip relationship at elevated temperature. The results indicate that the maximum bond shear stress of the joint lies in the range between 25 MPa and 28 MPa at ambient conditions, irrespective of the curing type. A rapid decrease in the maximum bond shear stress appears with exposure to the elevated temperature. Maximum shear stress reaches 10 MPa when the bond line temperature exceeds 90 0C. The elevated temperature curing, exposed temperature during service and the bond thickness notably affects on the bond slip behavior.
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-Full-text
Building performance of sandwich panels made out of building debris and stabilized earth
Jayathilake, KADSB; Jayasinghe, C
With the aim of promoting sustainable construction, several building materials with lower life cycle cost have been developed. This in turn would limit the over exploitation of natural resources used to produce conventional building material such as bricks and cement sand blocks. Building demolition waste has added to the environmental impacts created by the building industry. This paper covers a research carried out to investigate the possibility of using recycled building demolition waste (BDW) in constructing some building elements with a comprehensive experimental programme. BDW has been combined with stabilized rammed earth (SRE) which is another greener material, to construct a composite walling material. The optimum mix proportion of BDW and SRE was established together with other important material properties to assess the proposed material for acceptable building performance. Based on the results, the proposed composite walling system made out of BDW and SRE can be confidently used as a load bearing walling material.
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
A Case study on sustainable restoration approach for cascade pond systems in Jaffna municipal council area for effective flood management
(2019) Thilakarathne JASI; Rajapakse RLHL; Wijayaratna TMN
A unique characteristic of dry zone rainfall is its higher peak rainfall, even though the annual rainfall is relatively low. Jaffna peninsula is located in the northernmost part of Sri Lanka and faces these critical storm events during the second inter-monsoon. The pond system in the area was acting as the major water retention body, however due to the lack of awareness and proper rehabilitation, their retention efficiencies have severely been reduced. Research methodology was developed to check the effect of reservoir connectivity for flood mitigation. HEC-ResSim computer simulation application was used to model Paalkulam and Nayanmarkaddu kulam pond cascades in the Jaffna Municipal Council region. Model results were used to quantify the flood affected area and the results were validated based on a water balance model. Daily rainfall data of year 2017, pond survey (contour) maps, canal network and natural stream network were used. Two scenario analyses were followed to identify the reduction in inundation area after the inclusion of reservoir cascade behaviour and the two rehabilitation approaches for sustainable pond restoration. HEC-ResSim modeling was continued for scenario analyses, considering the insignificant deviations (6~8%) with the water balance model results. During the 2017 flood hazard, 27.5% of Paalkulam cascade catchment area out of total 156.7 ha was flooded and it was found that the affected area could have been reduced to 13.2% saving 21.73 ha area (14.3% of the Cascade land area), had the cascade connectivity been restored. The bund raising and bed dredging approaches showed a flood area reduction of 4.5 ha (20.2%) and 7.2 ha (33.3%) for downstream reservoirs and 5.8 ha (26.4%) and 3.9 ha (17.2%) for upstream reservoirs. Furthermore, the second scenario analysis for rehabilitation approaches confirmed that the most suited rehabilitation approach for upstream and downstream reservoirs are reservoir bund raising and reservoir bed dredging, respectively. Therefore, for a sustainable pond rehabilitation approach, proper accounting of the cascade connectivity is vital. Moreover, the best pond rehabilitation approach highly depends on the corresponding pond location in the cascade.
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
Comparative study on building materials for the construction of refuge space
(2020) Eric TB; Jayasinghe MTR; Lewangamage CS; Ibell T
With the effects of climate change, natural disasters are becoming more severe and more frequent, resulting in loss of lives and an impact on a country’s economy. Disaster resistant structures play a vital role in preventing loss of lives and damage to the belongings. As a consequence of a whole disaster resistant house being unaffordable, converting a part of the house to a disaster resistant refuge space could be attractive and could pave a way to build resilient communities. Selecting a suitable building material is a vital decision as they account for almost 60% of the total cost and govern the disaster resistance of the structure. There are many options to choose from alternative materials in addition to conventional building materials. One such alternative material is produced by recycling Expanded Polystyrene (EPS) wastes. It is the EPS based lightweight concrete (LWC) wall panels. This study aims at evaluating the material properties and characteristics of this construction method. A detailed comparative study was conducted in comparing the strength, durability, thermal performance, embodied energy and carbon footprint of the LWC panels to the conventional building materials: bricks and cement blocks. Furthermore, this study presents details of work study and cost analysis conducted on a full-scale model construction. The potential of LWC panels as a mainstream building material is shown with the comparative study. Moreover, this study presents the aspects of a survey conducted among experienced and young engineers, professionals, and the general public on the importance of material properties. This thesis also discusses a multi-criterion decision problem solved through the Analytical Hierarchy Process (AHP) in obtaining the most suitable material as a case study
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-Full-text
Detection and estimation of damage in framed structures using experimental modal data
(2020) De Silva WARK; Lewangamage CS; Jayasinghe M.T.R
The inevitable ageing and degradation of buildings and the structural failures that follow, have ignited a need for early prognosis of probable structural failures so that proactive measures can be undertaken. Hence, one of the important steps of structural health monitoring (SHM) process is the detection of damage and estimation of damage severity. Modal data can be effectively used for this purpose owing to their sole dependency on mechanical characteristics of a structure. However, the focus of mode shape-based damage detection techniques has concentrated only on symmetric structures whereas the existing buildings are typically asymmetric. This study presents a damage detection methodology using the behaviour of mode shape derivatives such as mode shape slope and mode shape curvature for a symmetric framed structure applied on an experimental model tested using a shaking table, and a calibrated finite element model. Furthermore, an extended parametric analysis has been performed to investigate damage localization and quantify severity. Finally, the models have been modified to incorporate the irregularity effects and damage detection possibility has been explored. The study enables to provide key conclusions for damage detection with respect to localization and severity in the steel frame model. Damage detection method using the mode shape curvature is identified to be more sensitive as opposed to mode shape slope method. And the effect of mass irregularity on the detection methods were identified.
item: Thesis-Full-text
Developing a natural acoustic barrier for urban areas
Senanayake, MAD; Halwatura, RU
Increasing noise pollution has severally effected the urban areas where noise generated by traffic is considered as the major noise polluter. As a solution to the noise problem using noise barriers is an approach proven to be effective but due to land scarcity and social needs in urban areas applying noise barrier solution is challenging. Using a natural barrier as a noise barrier is a promising approach. Natural barriers are large or small closely grown tree belts, vegetation walls, natural stone structures, tree fences etc. Natural barriers, have emerged as the new trend to address problems in urban areas and has developed into vertical gardening, green roofs and hybrid natural barriers presently. The use of natural barriers as a solution is highly dependent on the human perception. The research was carried out to identify the human perception and human acceptance of natural barriers in Sri Lankan context and find out the level of acoustic disturbance people are facing. Focusing urban and suburb areas a quantitative approach was adopted via a questionnaire survey and actual sound measurements were taken in the western province of Sri Lanka. Secondly field testing was carried out to evaluate the performance of existing natural barriers to identify their acoustic performance. Closely grown tree belts which assumes a cuboid shape were used as test barriers. Multiple Linear Regression (MLR) models Artificial Neural Network (ANN) models were used to evaluate the performance of natural barriers. Cuboid shape natural barrier with 85% of green cover or more and overall height closer to 2 meters or more has proven to be an effective acoustic barrier for urban areas.
item: Thesis-Abstract
Developing an activity pattern choice model for individuals in western province
(2021) Fernando D; De Silva GLDI
Transport demand models assess impacts of transport policies and transport infrastructure. In recent times transport modellers have been moving towards disaggregate activity based models from widely used aggregate trip/tour based models. Hence the unit of analysis has shifted from vehicle flows/trips between zones to individual’s activity patterns which in turn has aided in modelling complex human behavioural responses to current policy decisions. With Sri Lanka also moving towards activity based modelling in the near future identifying a suitable method to represent activity patterns of individuals is a key aspect. The research addresses the issue by developing an activity pattern choice model using home visit survey (HVS) data for individuals in Western Province. Based on HVS data activity patterns for each member was developed with each pattern consisting of spatial and temporal representation. 3 main categories (Education, Work & Other) were clearly identified and each member was assigned a category based on the most prominent trip in the pattern. The 3 categories were further categorized based on aspects of number of tours, purpose, diversions and time. 17 subgroups were identified which consisted of 5 work, 4 educational & 8 other pattern groups. The identified 17subgroups were used to develop the activity pattern choice model based on socio economic data. Initially a multi-level structure was considered. But due to the fuzziness of the results each level was considered as a single level and hence estimated separately. Each level consists of 2 choices and one choice is estimated relative to the other. Estimation of the 7 level choice model was carried out using “Apollo” module in R programming language. The developed choice model at upper levels of education and work patterns displays a high level of accuracy. But lower level of the model mainly the patterns related to other pattern groups displays fuzziness and hence displays a lower level of accuracy at these levels.
item: Thesis-Full-text
Development of a low cost insulation system using bottom ash for CFRP - concrete composites
(2020) Arachchi KADYTK; Gamage JCPH; De Silva GIP
The civil engineering industry is moving towards more greener and sustainable means of construction materials today. Improving the thermal comfort in buildings while conserving the natural resources is essential to maintain the ecological balance whilst improving health, wellbeing and productivity of humans. On the other hand, concrete structures have been the main construction element for the past five decades. Retrofitting these concrete structures using fiber reinforced polymer (FRP) has been a popular trend in the recent years. An insulation material has been developed using bottom ash which is a byproduct of the coal power generation process. The developed plaster could be used for either thermal comfort in buildings or as a cementitious insulation material for CFRP/Concrete composites. The research was conducted in four phases. Properties of bottom ash and properties of developed material were investigated in the first two phases. Modification of developed insulation material and application of CFRP/Concrete composites were investigated in the latter two phases. A N-type plaster was developed by replacing fine aggregates in conventional cement sand plaster by bottom ash. 60% of the sand was replaced by bottom ash. A thickness of 20 mm of the developed plaster can decrease the heat transfer 45% than conventional plaster. Furthermore, the developed plaster is 8% more cost effective than conventional plaster
item: Thesis-Full-text
Development of a methodology for pavement maintenance optimization and prioritization for provincial road network in Sri Lanka
(2018) Gunasoma HDS; Pasindu HR
Pavement management system is a decision support system that is used by highway agencies to maintain its road networks, extending their useful life within the available budget and resource constraints. Methodology of selecting maintenance strategies for authorities is an integral component of the pavement management system. Most current systems cannot be customized to reflect the local conditions with resources available and required extensive data collection and calibration, which are not sustainable for those authorities especially in developing countries. Thus, the identification of new approaches, which have been suited for the relevant factors in developing countries in pavement management, is a major requirement. The study focused on the existing pavement management systems, first it aims to identify the main constraints that affect the pavement maintenance planning and for formulation of the maintenance strategy in road agencies at provincial level. The main constraints and priority factors were identified by the opinion survey from the Engineers of road agencies. Based on the opinion survey five main priority factors were finalized namely pavement condition, traffic volume, connectivity to local road network, land use pattern and importance to community. An optimization model was developed to maximize the overall network condition whilst incorporating the priority factors identified in the study. Priority index of each pavement sections computed from the prioritization model is incorporated to optimization model. The proposed model is capable of determining the optimum maintenance activities for each road sections considering the budgetary, network condition and road section priority considerations. Applicability of the proposed model is illustrated using a case study consists with pavement sections with different attributes. Results from a case study using the proposed method show that the suggested maintenance and rehabilitation plans make sense from engineering and socio-economic considerations. Keywords: Pavement management systems, Pavement Maintenance, Optimization, Prioritization
item: Thesis-Full-text
Development of a resilience measurement tool to evaluate the community resilience
(2019) Perera GMCA; Siriwardana CSA; Wijayaratna TMN
The frequency of disasters and emergencies has increased rapidly during the past few decades and it is necessary to conduct more research in this field to improve the knowledge levels and capacities of individuals/systems. And subsequently this can assist policy makers. Instead of managing disasters after the outbreak, in the present situation the researchers are more concerned about improving the resilience of communities to face impacts. Under this background, methods to measure community resilience are vital because it can be used to identify the vulnerable communities and resilience scores can be used in the decision-making process. To assist the process, this research aims to develop a universal tool to quantify the levels of resilience of communities to the impacts. From the literature, indicators which are relevant to resilience measurements were listed, suitable indicators were filtered and then the method of measurement was defined. Overall, 108 indicators have been listed on this scorecard under five main capital domains, including, social, economic, physical, human and environmental. This list was sent to the experts and the index was refined based on the expert comments. To provide the resilience score, two types of scoring methods (Community Resilience Scores - CRS1 and CRS2) have been introduced in this dissertation where the first method uses a general approach to calculate the resilience and the second method uses a more descriptive approach including the four main disaster management phases (Mitigation, Preparedness, Response and Recovery). The scoring method has been defined to calculate the overall resilience, resilience to floods and resilience to droughts. The method has not validated yet and open for researchers to test this method. However, applicability of the tool is explained using a few case studies and these cases show the overall resilience values, values for resilience for floods and droughts in some selected regions in Sri Lanka. From the case studies, the overall resilience values (CRS1) show that social and environmental resilience is higher in the rural areas compared to the urban areas while the economic and physical resilience is higher in the urban areas compared to the rural areas. According to the CRS2 the response stage shows lower scores in many of the selected regions. Similarly, using the values of the proposed two matrices (CRS1 and CRS2), gaps in the major capital domains in a given administrative region can be identified and this is important to undertake further developments and for allocation of resources. The proposed scoring method can be used to prepare resilience level maps and to identify vulnerable regions as well. The study can be extended to improve the index to measure the resilience to other disasters, including hurricanes, landslides, tsunamis and other coastal hazards.