Doctor of Philosophy (Ph.D.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/12429

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item: Thesis-Abstract
Development of a hybrid air purification unit for the indoors in tropics
(2023) Weerasinghe, KGNH; Halwatura RU
Indoor air pollution poses a critical concern in today's world, influenced by various factors. Ensuring a safe indoor environment demands addressing the profound impact of pollution. Multiple strategies have been deployed to mitigate indoor air pollution, with a focal point emerging as biofiltration using indoor plants. This prompted a thorough exploration into the capacity of NASA-recommended indoor plants, which had undergone minimal experimentation in tropical climates. Simultaneously, an assessment was made on the efficacy of indigenous herb plants in curbing indoor air pollution. The plant selection process involved using a plant selection matrix to identify the most suitable plants for the study. Individual plant performances were rigorously tested within controlled chamber studies, evaluating their abilities to reduce carbon dioxide and other pollutant gases. The net performance of plant leaf area in carbon dioxide assimilation was measured and compared, resulting in a ranking of plants based on their performances. Among these categories, the Peace Lily (Spathiphyllum blandum) and Thippili (Piper longum) plants emerged as the top performers. Using these selected plants, a hybrid air purification unit was innovated, combining natural plant-based purification with modern technology and additional functionalities. Subsequently, the actual-scale performance of this developed system was assessed to determine its environmental sustainability. A comprehensive questionnaire was employed to gauge the social sustainability aspect. The plants' performances were also evaluated in air-conditioned settings, followed by an economic comparison to ascertain practical feasibility. The culmination of these endeavors has revealed that employing specific combinations of indoor plants facilitates achieving desired indoor air quality levels, particularly in terms of reducing carbon dioxide levels. This practice is beneficial economically and is highly recommended for indoor spaces where individuals spend approximately 90% of their time. Ensuring indoor safety becomes paramount, and this Hybrid Air Purification Unit not only contributes to energy savings and enhances environmental air quality but also encompasses the immeasurable aesthetic and therapeutic effects of plants. Keywords: Air Purification, Carbon Dioxide, Hydroponic Cultivation, Indoor Air Quality, Indoor Plants
item: Thesis-Full-text
Improving reliability in predicting the degradation of building assets
(2023) Wickramasinghe, GAVK; Dias WPS; Setunge S; Mallikarachchi HMYC
Predictive modelling of building component degradation optimises project management and maintenance costs. Typically, the visual inspection-based generic condition ratings of building components are collected over time and analysed to determine age-related degradation trends and corresponding life cycle costs. Using two datasets, this research proposes two new approaches: (i) deficiency-based (as opposed to generic) condition ratings of building components from seven local councils in Sri Lanka were analysed to develop Markov models at the component level (engineering-based approach); (ii) nominal replacement costs and times for building components assigned by estimators from the City of Melbourne were used to arrive at degradation rates for component groups through a novel concept of cumulative lost value ratio (CLVR) (monetary-based approach). In the engineering-based approach, snapshot data were collected using both deficiency-based and generic deterioration-based condition scales, and the Markov Chain Monte Carlo technique was used to develop reliability-based models. The results showed that deficiency-based models were more accurate and reliable. The monetary-based approach explored the CLVR concept and the validity of using Markov models for component groups, where stochasticity is based on component mix rather than degradation process randomness. The study's theoretical contribution was to interpret "degradation" in terms of curable and incurable deterioration from a maintenance perspective, estimate component maintenance-free ages using data screening, establish new monetary indices such as LVR and CLVR, evaluate the impact of influencing factors using GRG NLO categorisation, and utilise a monetary-based degradation forecasting paradigm utilising nominal cost data as an alternative to using physical condition data. In practice, the deficiency-based approach will directly improve predictive maintenance reliability, lead to longer maintenance intervals, convert deficiency-based ratings to cost-based ratings using the LVR-based index, and bundle maintenance through categorisation via degradation patterns. The monetary-based approach will eliminate inconsistent physical condition assessments and enable more building assets to be modelled. Keywords: Building components; Deficiency; Degradation; Markov modelling; Influencing factors
item: Thesis-Full-text
Development and validation of a novel CFRP/steel hybrid crack repairing technique for the steel structures
(2023) Abeygunasekara S; Gamage JCPH; Fawzia S
Steel structures such as steel bridges greatly contribute to the socio economic development of the world. The current traffic demand has exhausted the service life of steel bridges paving the way for failures without prior warning due to fatigue. In fact, fatigue contributes to change the microstructure of a material which fails below the yield point. Therefore, fatigue could be considered as an issue related to materials, even though it is linked to the area of engineering. Interestingly, several unavoidable stress types on structures occur on steel bridges due to various reasons. As a result, avoiding fatigue on structures has become impossible during their service life. The result of stress fluctuation has caused crack initiation on steel structures while the initial stage is at a micro scale level and not visible to the naked eye. Thus, it should be controlled at the initial stage avoiding adverse effects later. Although the conventional crack repair techniques have extended service lives of structures they have led to numerous drawbacks too. The crack stop hole technique could be considered as an emergency repairing technique to extend the fatigue life of a cracked steel structures that is quick, simple and economic. This technique was successfully applied in the aerospace industry primarily, however there had been irregularities due to the size of the hole with re-cracking appearing due to continuous service loads. Carbon fiber reinforce polymer (CFRP) materials have become popular as it has potential to replace the conventional repairing techniques with recent research focused on CFRP materials due to its light weight, corrosion resistivity, damping characteristics, fatigue resistivity and high tensile features. Therefore, this study proposes a crack stop hole (CSH) technique combined with a CFRP strengthening method to acquire the lost capacity due to fatigue in old structures with delaying re-cracking by further continue their services by steel bridges in the road and railway network operate at present. An experimental test program carried out to determine the behavior of strengthened and nonstrengthened CSH in steel members subjected to low cycle flexural fatigue. Overall, the test program was focused on estimating yield strength losses and yield strength gained by CFRP. Interestingly, various types of fatigue testing apparatus are available in the open market for a relatively high cost which is not affordable in a university laboratory, thus a hydro-electric controlling fatigue loading apparatus was designed and fabricated as an initiation to this research study to fulfill this vacuum. In this development process, machine operation, and development technique with finite element analysis on the test frame was investigated. In the next phase of this research, a numerical model was developed using an advanced finite element model (FEM) and results were validated using the laboratory test results. The proposed numerical model was based on the cyclic J-integral method under the detect cyclic mode. The test results agreed with the model results consisting nine key parameters affecting the final results. This CFRP strengthened CSH technique is significantly enhanced fatigue life of the structural members. This investigation reported the yield strength losses; which are in the range of 13.4 % to 25.2 % compared to the non-conditioned and yield strength gains with CFRP; which is in the range of 32.2 % to 45.3 % compared to the non-strengthened CSH with the diameter varies from 4 mm to 25 mm. A considerable amount of strain controlled were recorded by CFRP with respect to non-strengthened CSH. When considering the critical parameter effects, the test results recorded a yield strength gain with respect to off-set distance; which was in the range of 36 % to 131 % compared to the CSH at the midpoint. The yield strength variation recorded due to the length of CFRP layer was in the range of 89 % to 223 % compared to the least length considered. This investigation recommended by CFRP strengthened technique has significantly enhanced fatigue bearing capacity of structural members with CSH. Design guidelines are developed for practical implementations.
item: Thesis-Abstract
Coconut fiber reinforced polymer composite for non-load bearing panel walls
(2022) Dharmaratne P D; Halwatura RU; Nilmini AHLR; Jayasinghe R
The study's main aim was to develop a lightweight walling panel for apartment buildings by employing coconut [coir] fiber with waste polyethylene. In this study, the flexural performance of coconut fiber reinforced polymer [CFRP] sandwich panels with different core configurations has studied experimentally and numerically. The numerical investigation was carried out using finite element analysis software “ANSYS 17.2”. The coconut fiber reinforced polymer sandwich panel was developed with thin CFRP sheets for the outer faces and cell arrangement for the internal core structure which was made by the same CFRP sheets. The sequences of cells with different core structures were considered to determine the optimum solution for flexural behavior. The first part of this study was the investigation of coconut fiber's physical, mechanical, and chemical properties by using an experimental investigation and a literature review. The next step was to develop the CFRP composites. In this study, the coir fiber was used as reinforced material, and the waste polyethylene was utilized as a matrix material. Composite was developed using hand-layup techniques by varying the coir length and coir weight fractions. This composite material was analyzed using ASTM standards for tensile and bending performance. The sample which optimum results obtained relevant to the coir length and weight fraction were used to develop a composite sandwich panel of 400mm x 400mm in size. The most suitable manufacturing conditions were also studied. The flexural properties of this panel were inspected using experimental and numerical methods. The three-point bending test was carried out to investigate the maximum failure stresses for the panel sample. The next part of this study is to develop the numerical models for the three-point bend test using finite element software. Then, the experimental results obtained from the three-point bend test and numerical outcomes are compared and validated. In the end, the numerical analysis is expanded to examine the sample panel's flexural performance of different cell arrangements. Finally, the failure stresses and the volume at minimum failure stress were identified for each cell configuration. This result concluded that the best cell configuration with minimum weight for wall panels was the result. The proposed wall panel should be durable and low-cost. Therefore, service characteristics and production costs were analyzed. Further, to extend this research, the proposed wall system's life cycle cost and embodied energy were analyzed to identify the long-term benefits of the proposed walling system.
item: Thesis-Abstract
Integration of double skin green wall as a sustainable design approach in tropical context
(2022) Rupasinghe HT; Halwatura RU
Global warming and energy crisis are two of the biggest issues the world faces today which require immediate mitigatory actions. Building sector plays a major role in contributing to these issues due to the high energy consumption and carbon emissions. Highly dense urbanities directly contribute in urban heat island effect thus local warming. Therefore, researchers have given considerable interest on the building envelop design with the concerns for energy efficiency, aesthetic appearance and sustainability. As a result, integration of green facades with buildings has rapidly evolved due to the aesthetic appeal and sustainable benefits such as uplifting the urban environmental conditions by promoting air quality, reducing heat island effect and etc. However, adaptation of vertical greenery is still at an initial stage in Sri Lanka. The research was initiated to introduce vertical greenery to a broader context and to develop an innovative modular green wall system for building facades as a sustainable building envelop in Sri Lankan context. Field studies were conducted in identifying the potential of introducing a vertical greening system and benefits of existing vertical greening systems in tropical Sri Lankan context. Modular panel and green wall system development was conducted as on-site experiments and the thermal performance evaluation and long-term benefits of the proposed modular panel vertical greening system was conducted as on-site investigations combined with software simulations. Results of the field investigations on the perception on vertical greening in local context demonstrated that general public, building occupants and the building designers are willing to accept the vertical greening as a sustainable approach for buildings. Yet, lack of knowledge on the vertical greening systems, maintenance methods and their benefits and misconceptions on related costs have impeded the popularization of vertical greening. Identified existing vertical greening types in local context; living walls, indirect and direct green facades are beneficial in reducing the surface temperature of buildings where living walls recorded the highest temperature reduction of 10.15 o C. Internal air temperature reduction was recorded to be 2.21 o C, 1.82 o C and 0.66 o C by living wall, indirect green façade and direct green façade. Pilot and extended field investigations on plant selection for the proposed vertical greening system resulted in shortlisting two species, from which Axonopus compressus was selected as the best plant species where a maximum 10.08 o C external wall surface temperature reduction and 3.15 o C internal surface temperature reduction was recorded. The experimental studies on finalizing growth media resulted 1:1/2:1/2: 1/4 coir: sand: compost: soil ratio as the growth media with the best compaction and the permeability for the plant growth in the proposed vertical greening system. Proposed system is advantageous as it can be easily introduced to existing structures and as the panels can be handled separately allowing easy installation and easy replacement with minimum technical support. Size of the modular panel was finalized as 600mm (width) x 900mm (height) for easy handling and the fiber was selected as the material due to strength and durability. Developed walling system recorded a surface temperature reduction of 17.26 C in external wall and internal wall surface and a temperature reduction of 2.89 C of internal air temperature. Simulation studies conducted in building scale and urban scale resulted significant indoor air temperature reduction, cooling load reduction and urban air temperature reduction when integrating the proposed modular panel green wall whereas the quantifiable long-term benefits are achievable in terms of savings from energy consumption and façade maintenance and numerous un-quantifiable benefits related to sustainability and health.
item: Thesis-Abstract
A Dynamic, clay double wall system for indoor cooling
(2022) Padmaja RAM; Halwatura RU
Truly, sustainable development promises environmental, social, economic, yet personal meaningfulness, beyond increasing financial wealth. The usage of clay in construction is proven sustainable in all three aspects since its usage from the very beginning of human civilization. However, the chauvinism toward clay as a nonmodern material is detrimental, and therefore novel innovations of clay, are required to fasten with modern architecture for a whole new perspective. The usage of clay for primary, heavy walling is common in hot arid climates, yet fewer studies incorporate clay for interiors and double walling in the tropics. This gap was addressed by developing a Dynamic, Clay Double Walling (DCDW) solution for heat reduction with easy maintenance and favorable aesthetics. The cooling effect of these structures can be attributed to the resistance of heat flux to the building due to the porosity of the structure, heat absorption, and thus decline of thermal conductivity. The research thus investigates improvements in internal porosity and air permeability of clay, for improved mechanical and chemical properties, and thermal stability upon firing. Patterns and characteristics for best indoor air temperature reduction were identified on the material mix, mix composition, firing configurations, thermal conductivity, shrinkage, panel thickness, etc. The practicality and application potentials of the invention were tested on-site, potential improvements were tested virtually (with building simulations) for their effectiveness, and in completion, the long-term sustainability, and profitability of the DCDW system were investigated by identifying the LCC. The innovation suggests an energy-efficient, low-cost, low maintenance and lightweight, sustainable, double walling solution for high-end to low-end, yet new construction to retrofitting for tropical interiors.
item: Thesis-Full-text
Development of wall putty for tropics using drinking water treatment plant waste alum sludge
(2022) Galkanda GAHH; Halwatura RU; Nilmini AHLR
Water is the main source of life; therefore, a sufficient amount of safe water consumption is essential for public health. It is one of the responsibilities of a country, to ensure the access of its citizens to consume sufficient safe water. In Sri Lanka, the national water supply and drainage board (NWSDB) is the responsible authority for drinking water purification and distribution. NWSDB owned 323 water supply schemes. In drinking water treatment plants, surface water is collected and treated to drinking quality removing impurities dissolved in surface water. In the purification process aluminium sulphate (Al 2 (SO 4 ) 3 ) (Alum) is used as the coagulant and generated alum sludge at the end. The sludge disposal to surface water bodies creates the undesirable formation of mud deposits according to the activation of alum. Direct discharge of sludge into water bodies creates damage to its’ creatures and ecosystems. Therefore, direct disposal of alum sludge in open lands and water bodies is prohibited by legislation. Dewatered alum sludge is disposed at landfills and rock blasting wells. However, the increasing daily generation of sludge is creating an urgent necessity for a sustainable solution. The increasing amount of daily alum sludge production has considerable environmental and economic concerns in most countries. Therefore, the world's attention turned to finding a sustainable way to reuse or recycle DWTP alum sludge. This research aimed to address the issues mentioned, by developing a wall putty using waste alum sludge generated in drinking water treatment plants (DWTP) in Sri Lanka. Properties of the DWTP waste sludge differ according to the climatic conditions, geographical conditions, water treatment process and raw water quality. The research was conducted after the identification of the properties of DWTP waste alum sludge of different plants. Laboratory experiments were conducted to study the properties of sludge samples collected from DWTPs in Ambathale, Biyagama and Kandana. Biyagama DWTP was selected to collect sludge for the study due to the low moisture content and high solid content compared to other samples. Waste sludge is discharged at the end of the water treatment process, in semisolid form with high moisture content and it is dewatered through a sludge treatment process in Biyagama DWTP. Dewatered sludge generation of the plant is estimated at 10m 3 per day. Properties of DWTP waste alum sludge were studied. According to the results, moisture content variation, volumetric shrinkage variation, chemical composition and heavy metal analysis of the sludge was analyzed. In the first phase of the study, experiments were conducted to develop a wall putty mix using wet alum sludge. Test results reveal that volumetric shrinkage can be reduced with physical additives and adhesiveness can be improved with binders, but a wall putty mix cannot be developed with wet sludge by mixing additives and a binder, due to the high moisture content, high shrinkage and alum activation. In the second phase of the study, experiments were conducted to develop a dry powder from wet sludge overcoming the alum activation. To that thermal alterations of DWTP waste alum sludge were studied. Colour and density variations of the burned sludge at different temperatures were studied. Sludge becomes harder when burned, due to the alum activation and none of the processes that exist in the world, to produce dry powder from DWTP alum sludge. Alum activation of the sludge can be overcome by burning sludge with a lubricant. According to the experiments, coconut oil is identified as an effective lubricant. The density of burned sludge with oil is lower than that of burned sludge without oil at each temperature. Finally, a process was developed to produce dry powder from DWTP alum sludge. In the final phase of the study putty properties of the developed dry powder were analyzed and optimized and the performances of the developed wall putty mix were analyzed compared to existing wall finishes. And the real scale performances of the putty were tested. Finally, it was concluded that the developed dry powder is applicable as a wall finisher successfully on both interior and exterior walls. And also new research areas were identified for further studies from this research.
item: Thesis-Abstract
Decoding the potentials of vernacular timber preservation technology for structural applications
(2022) Mendis MS; Halwatura RU; Somadewa R; Amarasekara H; Jayasinghe R
ABSTRACT Along with the celebrated history in the field of construction in the world, wood has been a building material for hundreds of years. The stability of timber structures is influenced by their reliance on external factors as it’s a hygroscopic material. Where the moisture content has an impact on almost every structural parameter, including strength, stiffness, and dimensional stability. It is also extremely vulnerable to biological degradation caused by insects, fungi, and bacteria affecting the molecular structure. These scarcities were undertaken in traditional wooden structures in a significant, yet sensitive manner in a tropical country like Sri Lanka. The durability of traditional wooden constructions exists under a highly appreciable status. In a tropical environment, the prolonged physical sustainability of wood is a challenging task. These show a greater degree of tolerance in the harsh tropical environment. Empirically expressive information sources were investigated, therefore structures for shelters were selected for further analysis. In this case, Tampita Vihara (the shrines on pillars), Devala (shrines dedicated to deities), Ambalam (resting places for travelers), and Mandapa (the assembly spaces for administrative practices) of which physical remains are still available in a relatively preserved state of standing evidence were carefully chosen. Numerous literature findings are documented on their religious beliefs and the significance of their architecture. But the structural engineering aspects relevant to material perspectives have not been studied adequately. A holistic investigation of timber in construction was carried out using knowledge from traditional vernacular buildings. Traditional vernacular v 1 construction relied on a thorough awareness of the surrounding environment, as well as the characteristics of locally available materials and manual labor. Traditional people are essential stakeholders in forest management because they are often economically, socially, and culturally reliant on forests. This resulted in building artisans attaining a profound knowledge of the utilization and manipulation of materials. This study examines the state of the structures, which entails a thorough understanding of past and present conditions. The goal of collecting extensive data from various typological structures is to establish a knowledge basis for the future. Field survey analysis around Sri Lanka was conducted to accumulate and consolidate the traditional vernacular timber processing and preservation technologies. Results disclosed wood logs burying under paddy field mud as a well-established technique to treat wood. As well, three dominant plant species were identified as Mikania micrantha, Titonia diversifolia, Gliricidia sepium assorted with paddy field mud to enhance the properties before treatment. Further, the field survey results and the microscopic investigations proved Mangifera indica wood was used for roof elements utilized after the above treatment in traditional vernacular structures with in the use life range 40 to 50 years. This showed its potential to be used for structural applications after proper treatment. Finally, an experimental trial was performed to evaluate the traditional vernacular technology with amendments, reinventing two types of wood preservatives based on the material matrix as plant extracts assorted with paddy field mud and only plant extracts obtained for water. This combination of traditional vernacular and contemporary aspects could offer an interesting and profitable approach to the further development of the wood industry. Keywords: Timber architectural typologies; timber preservation technology; Mikania; Gliricidia sepium; Titonia diversifolia; Plant extracts; wood preservatives. 1 The term vernacular comes from linguistics, where it refers to language usage specific to a time, region, or group.
item: Thesis-Abstract
Management of flood risk with spatial planning
(2021) Herath HMM; Rajapakse RLHL
Flood risk has become a significant issue particularly in urban regions of Asia. Climate change will intensify existing flood vulnerability and further strengthen it due to socio-economic inequalities. A new set of problems are created by the traditional decision-making of flood management in the face of climate change and rapid urban development. The concept of the socio-ecological system suggests that resilience is the key to managing complex systems and reducing flood vulnerability. In addition, recognizing the significance of nonlinear and nonstationary interactions of flood risk in decision making has highlighted the transition of flood management towards Flood Risk Management (FRM). Acknowledging the uncertainty associated with flood risk has become a key aspect in decision-making. Decision-makers agree on the need for adaptive and integrated policies and strategies of FRM rather than modifying the flood and making it easier to cope with by eliminating the highest probability of floods. Flood resilience embeds the incorporation of spatially distributed land-use policies, strategies, and guidelines which are a must for the management of flood vulnerability. As a result, the characterization, assessment, and management of flood risk were subjected to a critical review during the past years. Risk-based flood management is yet in its early period of development. Though the theory has advanced over the years, there still are visible shortcomings in the operationalization of the concepts and methods, mainly due to the lack of a framework for clear recognition and understanding of the components of the FRM system. The FRM and spatial planning domains have developed their knowledge bases separately over a long period. Recently, FRM and spatial planning have begun to share a similar perspective in the decision-making process. The role of spatial planning as an integrated planning tool has been emphasized in the decision-making of flood risk management. It is largely evident that as at present, the role of spatial planning in flood risk management remains inadequate mainly because of the absence of a common framework for stakeholders’ integration. The main objective of this research is to identify the complete FRM system and its components with recommendations for its operationalization. This research has developed a solution model to structure the complexity of the planning process of FRM. The criteria and sub-criteria of the conceptual framework of the decision model have been identified based on the systematic literature review. Further, the criteria and sub-criteria of the conceptual framework have been selected and prioritized using the Delphi technique and Analytical Hierarchical Process (AHP). Forty-two experts have participated in this research and the established framework has been validated using a case study. Panadura urban area which is located in the coastal wet zone and Colombo Metropolitan Region has been selected as the case study area for application of the framework. This research has established a methodological framework for the operationalization of FRM. The main criteria which determine the practicing of FRM are the conceptualization of flood risk in the planning process, assessment of flood risk in the planning process, as well as the discourse of the governance structure, and the available participatory tools in the context. This study has identified and prioritized sixteen sub-criteria to manage the uncertainty in the planning process. The established framework can be used to identify the strengths and the weaknesses of the planning process in a given context and to guide the planning process to operate risk-based flood management objectives, strategies, and guidelines. The established framework can be used to evaluate the alternative options of flood risk management for achieving flood resilience. The case study has revealed that the existing decision-making process of FRM does not recognize the complex interdependencies between flood risk, spatial form, and spatial planning. As a result, the current practices of FRM are unable to achieve flood resilience. Therefore, this research recommends the integration of FRM with spatial planning. The developed framework is more sensitive to the governance structure of the context, therefore more case studies are needed to conduct in different governance contexts for further refine
item: Thesis-Abstract
Development of soil based flooring material for tropics
(2021) Galabada GH; Halwatura RU; Nilmini AHLR
The unplanned and rapid growth of developments has led to adverse impacts on the climate and biodiversity. Among them, the building industry is one of the foremost sectors. Therefore, the proper selection of building materials and techniques is of prime importance. Out of several sustainable materials, the soil has gained more attraction due to its advantageous features. Hence, this century has seen several notable milestones after passing thousands of years with the usage of soil in construction. Earthen flooring is one aesthetically attractive building element that has recently been restored and modernized. In fact, terrazzo, ceramic tiles woods, etc. are the widely available flooring materials associated with certain undesirable features. Hence, a necessity has arisen to seek alternative flooring materials. However, soil as a flooring material has not been investigated properly. Therefore, this research focuses on developing soil as a flooring material with sustainable features while pursuing possible means of increasing the strength of soil as a flooring material and enhancing the top surface finish. Then, the durability and service characteristics, cost benefits, thermal performance would be evaluated with the behavior on a real scale. The optimum soil gradation was first investigated. Next, investigation results showed that the increase in water content causes a decrease in the compressive strength, linearly at a constant rate for all cement percentages. The selected soil cement mix with water form a concrete and 150 mm standard cubes were used to determine the compressive strength. The best size and shape of test specimens were predicted and the relationship between compressive strength and specimen size and shape was identified in this background. Consequently, soil concrete was tested with the addition of metal as a course aggregate, but it did not influence the improvement of compressive strength in a significant level. Soil concrete with chemical admixtures showed that the admixtures were useful to enhance the workability and strength. The Mixed proportion consisted of fine particle contents 0-10%, a sand content 55%-60%, gravel content 30%-35% with a maximum gravel size of 25mm. The required cement was 18%-20% that depended on the usage of the admixture. The required moisture range was 16%-19% for soil concrete without admixtures to achieve a workable mix. To form the top surface to be architecturally attractive and for smoothness with regard to user comfort, the surfaces were smoothened in this background. Among several resins, one synthetic resin and floor sealer were selected and applied on the prepared soil floor samples as a surface coating. The Phenol-formaldehyde (novolac) resin was selected and cured with the Hexamethylenetetramine (HMTA) with heat treatment. The bonding capacity of coating in the soil floor, the water absorption, the abrasion resistance, the slip resistance and the stain resistance were analyzed according to the relevant standards to evaluate the soil floor with the resin coating for durability and service characteristics. Though all the tested parameters were within the standard requirements, the abrasion resistance of resin surface failed in this context. However, the floors which were with floor sealers showed positive results. At the end of the series of experiments, the mixing proportion, the top surface finishing material and the method of construction were decided for the continuation of the research. Thermal performance and cost benefits were then evaluated and compared with other selected existing floorings. According to the temperature variation pattern, the soil floor showed a significantly low top surface temperature compared to the other floorings and indoor air temperature. In fact, the Life Cycle Cost (LCC) for soil floor is significantly less compared to other existing floorings. Finally, the study findings suggest that soil could be used as a flooring material and a floor sealer could be used as a top surface finishing layer with a long-term sustainability. However, further research is required to find the suitability for a building's upper floors and the use of natural resin as a top surface finishing material.
item: Thesis-Abstract
Innovative approach to produce soil - based building products
(2021) Malkanthi SN; Perera AADAJ
Soil as a building material has been used in different forms which include mud, adobe, rammed earth and bricks. Also, Compressed Stabilized Earth Blocks (CSEBs), a form of soil blocks with different additives, including cement, fly ash, and lime, have been investigated by many researchers for their advantageous properties. A literature review established that compressive strength significantly depends on the clay and silt (finer) content and 25% finer content produces the optimum results. However, investigators have not considered the amounts of other large particles. Furthermore, most of the researchers have adopted the method of adding different materials to soil in order to reduce the finer content in the soil. This study focused on an innovative approach to reduce finer content by washing and to utilize finer part of soil for different soil-based products simultaneously. Washing of soil is introduced as a method to reduce the finer content and soil with reduced finer content was investigated for production of compressed stabilized earth blocks. Further, the water re-cycling and its optimization for the washing process too was investigated. The separated finer content together with fly ash was investigated for the production of other soil-based productions namely roof tiles and burnt-bricks. This study also investigated the use of theories of particle packing optimization which changed the soil grading while enhancing the properties of CSEBs. It established the changing of soil particles in different ranges to fit the soil grading to an optimization curve. Moreover, the use of fly ash as a finer replacement to the washed soil produced significant improvements in CSEB properties made with washed soil compared to that of CSEB made with un-washed soil. Laboratory testing clearly showed that the use of washed soil with 5%-10% finer content improved the compressive strength of the CSEB by 50% with different percentages of cement stabilization. In addition, significant improvements in dry densities and water absorption ratios of blocks were also observed with this particle size distribution modification. Industrial scaled soil blocks made with the selected optimum finer content of 7.5% and 7% cement stabilization verified that the blocks properties meet the requirements given in the standards SLS 1382 and SLS 855. The soil washing process reduced the finer content in the soil producing a considerable amount of finer that could be used to produce building materials like roof tiles and burnt bricks. This extracted finer alone was difficult to be used, however adding fly ash gave significant enhancements to properties of roof tiles and burnt bricks. In fact, the study showed that 25% addition of fly ash to the extracted finer was more desirable. Roof tiles made with extracted finer and 25% of fly ash reported that the breaking strength, water absorption and permeability of tiles meet the requirements given in SLS 2. Burnt bricks made with extracted finer and 25% of fly ash also reported that the compressive strength, water absorption, and efflorescence meet the requirements given in SLS 39. Moreover, the properties of wire-cut bricks made with extracted finer and 25% fly ash also satisfied the requirements in SLS 39. The process optimization established that up to 60% water can be re-cycled. Cost analysis for the building materials considered in this study showed that the unit price of each product was significantly low compared to the current market price. Therefore, further research could be done to streamline all the processes and products considered in this study.
item: Thesis-Abstract
Performance evaluation frame work for service quality improvements in public bus transport
(2021) Sharic, AHS; Bandara, JMSJ
The aim of this thesis is to develop service quality measurement methods for bus transport considering two main components: passenger expectation and service performance. Existing measures of passenger expectations do not address the heterogenic characteristics of passengers. Existing measures on bus transport service performance lack consideration of possible dynamic elements of bus operations, such as thresholds for service quality factors, stop level, route level, service headway, bus size etc. There is a need for regulators to monitor the progress of achievement in sustainable transport through public transport service quality improvements. The thesis answers the questions about to what extent the levels of service quality are expected by the bus transport passengers and what is the existing level of service performance of the bus transport operation. Walking time, waiting time, travel time, in bus environment, and station environment are identified as important bus transport service quality factors for passengers. Conjoint analysis is used to measure the weight of passenger expectations on bus transport service quality factors using customer satisfaction surveys on service quality attribute levels. The normalization approach was introduced to address the heterogeneity of passenger behavior. The Threshold Enabled Earliness Index was developed to evaluate the reliability of buses (waiting time) at bus stops for both arrivals and departures using data on scheduled and actual arrival and departure times of the buses at stops. The Threshold Enabled Probability value is created using cross tabulation analysis to evaluate bus travel time reliability (travel time). Two Passenger Comfort Level Indexes STPCLI & SEPCLI to capture standing and seating passenger comfort levels are proposed that could be estimated using boarding and alighting counts. These two indexes are capable of capturing comfort levels for the entire route or a part of a route and not confined to a given location. In the absence of route level income information, methods have been developed to estimate bus revenue when individual passenger boarding and alighting data is available, or cumulative boarding and alighting data at the fare section level is available, or when only demand information or the history of demand distribution is available. A computer algorithm for estimating STPCLI, SEPCLI and to estimate fare revenue at route or part of route for different demand levels at different service headways for different bus sizes is developed. This algorithm could capture the number of passengers iii who would miss a bus due to capacity limitations and is useful in situations where limitations on loading need to be imposed especially to maintain social distancing. The study helps identify the bus transport passenger expectations about the quality of the bus transport service and it also helps to evaluate the service performance of the bus transport system in fulfilling those expectations. These measures can be used to compare the level of service quality among different sections of a bus route, for the entire route, among different routes or for an area and among different areas. This study finally contributes to the ongoing debate on the critiques of the operationalization of service quality measurements. Keywords: Service quality, bus transport, passenger expectation, service
item: Thesis-Abstract
A Reliable potable water purification system using nanomaterial-incorporated matrix for households in CKDu prevalent areas
(2021) Sudasinghe MI; Jayaweera M.W; Manatunge J.M.A; Gunawardana W.B
Chronic kidney disease of unknown aetiology (CKDu) in Sri Lanka is a national concerning health hazard as those affected face high mortality rates per year. One hypothesis on the disease pathogenesis is long-term exposure to fluoride, hardness, and cadmium in drinking water and their synergic effects, which causes nephrotoxic health hazards. Removal of fluoride, hardness, and cadmium is paramount in providing safe drinking water to the community in CKDu areas. However, available water treatment technologies in such areas do not offer an appropriate solution to drinking water issues. Hence, there are prerequisite to developing a reliable water purification unit to provide safe drinking water. This study investigated the best combination of materials to remove fluoride, hardness, cadmium, and faecal coliform in water to develop a reliable water purification unit to protect the community health and enhance their well-being. Firstly, nephrotoxic risk factors in drinking water, their threshold levels, and the level of components required to remove complying with the required drinking water guideline values were evaluated. Water samples collected reported hardness in the range of 111.73 ± 1.41 – 680.33 ± 1.53 mg/L as CaCO 3 and fluoride 0.72 ± 0.03 mg/L and 2.84 ± 0.05 mg/L. The cadmium concentrations reported below the detection limit of 0.025 mg/L. Literature reported that fluoride (0.1–13.7 mg/L) and hardness (63.6–1921.0 mg/L) concentrations in water are very high. Fluoride concentrations in most CKDu prevalent areas exceed the drinking water guideline value (1.5 mg/L). The World Health Organisation does not declare a health concern permissible value to hardness in water. The cadmium level was reported in trace level in potable water less than the permissible drinking water guideline value (0.003 mg/L). Nephrotoxic drinking water guideline values should be declared for CKDu prevalent areas to control the spreading of nephrotoxic health hazards. In non-CKDu prevalent areas, potable water hardness values were often reported below the level of 120.0 mg/L and fluoride around 0.2 mg/L. Hence, potable water consumption with a fluoride level of around 0.2 mg/L, hardness 120.0 mg/L and cadmium 0.003 mg/L will control the occurrence of CKDu. Available water treatment technologies introduced in CKDu prevalent areas were evaluated to identify their effectiveness in removing fluoride, hardness, and cadmium. Reverse osmosis, twolayer and seven-layer filter units have been introduced, treating potable water as a short-term II solution for the disease. The reverse osmosis unit removes most of the ions in water, retaining beneficial ions less in hardness 4.0–20.0 mg/L, high in fluoride 0.29–5.5 mg/L for human intake. The other two filters (two-layer and seven-layer filter units) do not remove fluoride and hardness effectively and add more ions into treated water due to the leachability in some minerals in the media. Treated water does not meet the required drinking water guideline values, highlighting a new requirement for water treatment units. The risk assessment for RO treated water was conducted to identify non-carcinogenic health effects in long term consumption. Hazard’s quotient values of different age categories did not exceed the value one (1 > HQ) for a short duration of water consumption. Children (Age category 1-9 years) are highly vulnerable to non-carcinogenic health hazards, and their HQ value exceeded one (HQ > 1) within a short period for fluoride (80 days), calcium (1,440 days), magnesium (2,160 days), and cadmium (360 days) before other age categories. HI mean values with higher concentrations elaborated that multicomponent concentration combinations bring adverse health effects on females in 1–9 and 10–19 years of age categories and males after 20 years of age. With mixture of component, age category 1–9 years exceeded HI>1 within 2 weeks for higher concentrations of the mixture, age category 10–19 years within one month, age category 2–90 years withing three months. The higher concentration value of components makes people vulnerable for adverse health hazard within short period of exposure. Long-run consumption of RO water causes non-carcinogenic health effects. Hence, developing a new water treatment unit is of utmost importance to provide safe drinking water. The modified fly ash (Zeolite) (ZEOL), MgO loaded alumina (MOMA), silver oxide nanoparticle + graphene oxide composite (SONPs + GO) proposes the best combination of materials to remove hardness, fluoride, and faecal coliform in potable water after conducting batch and fixed-bed column studies. The fluoride (Q = 18.76 mg/g) and hardness (Q = 263.16 mg/g) experimental data aligned with the Langmuir model for batch studies. The fluoride and hardness data corroborated with the Thomas model for fixed-bed column studies. The length of unused bed values was calculated as 1.62 cm, 1.00 cm, and 0.81 cm for ZEOL, MOMA, and SONPs + GO when each material's breakthrough points were considered the maximum allowable concentration. The height of the ZEOL bed required to remove hardness for three months of service period was calculated as 29.09 cm with the mass of adsorbent 2.63 Kg, 18.86 cm adsorbent bed height including the mass of 1.37 Kg of MOMA, and 6.48 cm with the mass III of 1.09 Kg of SONPs + GO. The cost of 1.0 L of treated water production was approximately Rs. 8.80 and the total cost for 10.0 L of water (daily consumption of a family) was estimated at Rs. 88.00. If a family of five household members consumes water for three months, the cost of treated water production was calculated as Rs. 7,920.00 (monthly cost Rs. 2,640.00). The best combination of multi-layer materials is a promising water treatment unit to remove fluoride, hardness, and faecal coliform in drinking water. Therefore, the fabrication of a multi-layer home filter unit using ZEOL, MOMA, and SONPs + GO is recommended to provide safe, clean potable water for the community in CKDu prevalent ares.
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Risks of inadequacies of inputs of preconstruction activities to design phase on cost and time overruns in construction projects
(2021) Daluwatte, L; Ranasinghe, M
Cost and Time overruns are common occurrences in construction projects completed in Sri Lanka. This research study was carried out to find the possible reasons for these overruns. The objectives of the study were to review, identify and analyze risks created by the inadequacies, correlations, coherence and accuracy of the input data of pre-construction activities to the design phase of construction projects and to develop and validate an industry best practice framework/model/guideline to minimize/eliminate cost and time overruns of construction projects due to risks of inadequacies, correlations, coherence and accuracy of the inputs of pre-construction activities to the design phase of the projects. Initially, contributory factors for Cost and Time overruns of construction projects were identified. ‘Design effects’ was found to be the critical contributory factor. A study on ‘Design effects’ identified the pre-construction activities that are input to the design phase of construction projects. These pre-construction activities were used to examine ‘Relevance of the activity’ and ‘Adequacy of the input of the activity’ to the design phase in a construction project. Accordingly, a model, “z = 100 - 2.6916e0.024x” where ‘Inadequacy of the input to the design phase (z)’ and ‘Relevance of a pre-construction activity (x)’ was derived for the input of a pre-construction activity to design phase of a construction project. Pre-construction activities were expanded and analysed to assess the risks created by inadequate inputs from the pre-construction activities to the design phase of construction projects as follows. Scientifically developed questionnaires based on the mixed type of research method and where internal consistency was rated as ‘excellent’ were used for data collection. The probabilistic random sampling method confirmed that the sample of respondents selected for the study was adequate. One questionnaire was used to collect data from 32 projects to examine ‘Relevance’ and ‘Adequacy’ of input from pre-construction activities to the design phase of construction projects. The other questionnaire was used to collect data from 100 projects to examine the possibility of eliminating/minimising the Risk of Cost overruns and Risk of Time overruns by retaining services of a third-party independent designer to verify the adequacies of input from preconstruction activities to the design phase of construction projects. All respondents to the questionnaires were substantive experts actively involved in construction projects. A structure to collect data was developed to identify and analyze risks from the input of respective pre-construction activities to the design phase of construction projects. The developed framework analysed risks using Risk Matrix, Relative Importance Index (RII), Severity Index (SI), Descriptive Statistics, Sampling Adequacy, Reliability, Validity, Correlation and Accuracy of data, Biases, Coherence of responses and Calibration of respondents. Guideline for industry best practice was derived by using scientific techniques of data analysis for risks created by the inadequacies of input from respective pre-construction activities to the design phase of construction projects. Results from the analysis satisfied the limits set by each scientific technique used for the analysis. The analysis highlighted the ranks of preconstruction activities which with inadequate input to the design phase of construction projects increased the Risk of exceeding Cost, Risk of exceeding Time and minimising the Risk of exceeding Cost and Time. Risk interpretation revealed that top ranks of preconstruction activities were ‘Likely’ to induce Risk of exceeding Cost and Risk of exceeding Time of construction projects. Guideline for industry best practice was validated through statistical methods and Case studies from the construction industry. The main conclusions of the study were that: i) Inadequacies of input from preconstruction activities to the design phase contributed towards Cost overruns and Time overruns in construction projects; ii) Risks created by the inadequacies, correlations, coherence and accuracy of the input data of pre-construction activities to the design phase of construction projects contributed towards Cost overruns and Time overruns in construction projects and iii) Verification of the input from preconstruction activities to the design phase of construction projects by a third party independent designer would minimise the Risk of exceeding Cost and the Risk of exceeding Time of Construction projects. In addition to the 3 main conclusions described above, there were 19 conclusions and 3 recommendations.
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Development of advanced design criteria for stronger lattice towers
(2021) Gunathilaka AMLN; Jayasinghe MTR; Lewangamage CS
The key lateral loads acting on a freestanding telecommunication/broadcasting tower are due to wind effects though occasionally seismic forces also can act. Though earthquake design guidelines are well covered directly or indirectly in many tower designs standards, telecommunication/broadcasting towers in Sri Lanka and in Indian subcontinent are not specifically designed for earthquake induced forces. Therefore, a detailed study was undertaken to determine the probable structural performances that can be expected from commonly adopted Four leg and Three leg self supporting lattice towers. For this study, the earthquake levels that can be possibly expected in Sri Lanka and in the South Asian region have been considered. A key parameter that can directly affect the seismic performance is subsoil conditions. Hence, a probable range of subsoil conditions have been considered in this study as certain subsoil conditions could amplify seismic waves under certain conditions. For a range of tower heights that are generally used, Response Spectrum analysis techniques have been used to assess the probable performance of lattice towers. An assessment was also made with equivalent static method to determine the applicability of it over a wide range of conditions. One of the key observations has been that the earthquake induced stresses on key members of lattice towers could be of lower magnitude than due to effects of wind. The parameters that could affect the seismic behaviour of a lattice tower are the subsoil stratum and the natural period of vibration of the lattice tower. The main finding of seismic analysis of lattice towers is that for the likely seismic hazard levels in Sri Lanka, key elements of towers will be subjected to much lower stress levels than induced by the winds of design magnitudes. However, if more severe earthquakes that could occur in the South Asian region are considered, there is a possibility for the earthquake induced forces to reach structurally significant levels. However, still such forces are less than the wind induced forces. For both earthquake and wind induced lateral loads, one of the key elements that needs careful attention is the connection of the tower to the foundation through baseplates. Baseplates are crucial elements related to structural stability of self supporting lattice towers. It acts as the interface between the tower body and the foundation. iii Due to structural characteristics of towers, uplift forces induced on baseplates govern the design of the baseplates. This is a rare case to occur on baseplate of buildings and other conventional structures. Hence, guidelines published in design codes and standard text books for design of baseplates are not really applicable for self-standing towers. This is a gray area that needs attention. Hence, an extensive study was carried out in this regard using Yield line theory to develop a design guideline. The developed theory was verified through a detailed experimental investigation and a finite element modeling using computer aided non liner modeling techniques. The formulae developed were modified for industrial applications considering all practical deviations which could not be addressed under fundamental theory using extensive parametric analyses carried out with the Finite Element models. The findings have been presented as design guidelines in the form of equations that can be used by structural design engineers undertaking free standing tower designs.
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The effect of firing temperature on micro-structural properties of non- expansive clays in development of effective internal curing concrete aggregate
(2020) Bandara MMHW; Mampearachchi WK
Internal curing concrete provides number of advantages in the concrete construction industry. It provides adequate water to hydrate all the cement. Moreover, internal curing increases the durability, compressive strength and eliminates the formation of shrinkage cracks. The most popular internal curing materials are the manufactured and natural lightweight aggregates. Those aggregates generally produce using expansive clays. Natural lightweight aggregates and expansive clay mines are not available in most countries limiting the production of internal curing concrete to a few countries. Moreover, those aggregates have various disadvantages in use of internal curing concrete production. Mainly, it reduces the compressive strength of concrete. Furthermore, some aggregates have lower water absorption capacity, and some have lower water desorption capacity. Thus, the main focus of this research is to develop an effective pore structure for internal curing aggregate using non-expansive clays. Different clay samples were obtained from local mine in Nachchaduwa, Dankotuwa, Metiagoda, and another clay sample was imported from China. Subsequently, those were chemically analyzed, and the percentage of each chemical composition was obtained. Afterwards, selected clay types were identified as bloating and unbolting clays according to the method that was suggested by Charles M. Riley. Nachchaduwa and dankotuwa; Metiagoda and China clay samples were identified as bloating and unbolting clays respectively. After that, the level of expansion was identified based on the bloating coefficient. All the clay samples showed lower bloating coefficient than 2.5. Thus, they were categorized as non expansive clays. The requirements for effective internal curing aggregates were identified through an extensive literature review and limits of those parameters were defined based on the literature review. Moreover, a aggregate production process was established by considering various effect of clay heating on development of pore structure. The effective range of heating temperature of each clay type was identified according to a simultaneous thermal analysis. Subsequently, clay specimens of equal sizes were prepared using each clay samples and heated at selected range of temperature to produce various pore structures within the clay specimens. Afterwards, heated samples were cooled, crushed, and fine aggregates were produced. Pore size, pore connectivity, pore strength and the pore expansion of each aggregate were identified through an extensive analysis of the pore structure. Afterwards, the aggregates were categorized based on the properties of the pore structure of each aggregate. The internal curing properties of those pore structures were measured based on water absorption, water desorption and density of the aggregates. Afterwards, performance of those pore structures was identified, and limits of the effective pore structures were defined. Bloted nonexpansive clay materials were identified as the most suitable materials to produce effective pore structure within heated clay mass. Conversely, unbloted non-expansive materials were not suitable to produce internal curing aggregate. According to the research findings, the effective pore structure should contain at least 27% of open porosity. The mean pore radius and the pore expansion should range from 0.3 to 0.5 m and from 1.1 to 1.5 mean bloating coefficient respectively. Furthermore, the compressive strength of pore structure should be greater than 10N/mm2. Finally, two different aggregates which have the effective pore structure and less effective pore structure were selected for verification process. The selected aggregates were produced in larger scale using industrial facilities of Rajarata and Midaya factories. Subsequently, three different types of grade 30 concrete were prepared from each aggregate type to validate the effectiveness of pore structure. Those concrete types were external curing concrete (ECC), nonii curing concrete (NCC) and internal curing concrete (ICC). Moreover, internal curing concrete with 3 days external curing (ICC/3EC) was prepared to study the combined effect of external and internal curing. ECC specimens were kept under submerged for curing, ECC/3EC samples were kept in submerged only for 3 days. NCC and ICC specimens were kept in open space. During the preparation of concrete specimens, workability of the samples was measured. Afterwards, concrete specimens were tested to obtain the compressive strength values at 7, 14 and 28 days. Subsequently, the drying shrinkage of the internal curing concretes which contain the selected aggregates was measured. According to those results, the aggregates which contain the effective pore structure exhibit effective internal curing properties while other aggregate failed to act as an effective internal curing aggregate
item: Thesis-Full-text
Influence of indoor environment on sick building syndrome
(2020) Perera TM; Jayasinghe C; Perera SAS; Rajapaksa SW
People spend most of their time indoors, either at home or at work. Therefore, it is essential to maintain a high level of health and safety inside all types of buildings. The phenomenon where the health conditions of the occupants are adversely affected due to the indoor environment, it is called “Sick Building Syndrome” which is abbreviated as the SBS. The origin of indoor air pollutants is mainly categorized into three distinct sources. They are building materials and related human practices during construction and operation stages, outdoor sources and the prevailing ventilation condition of the structure in the discussion. The importance of studying in-depth of the causes and prevention of SBS, lead this research to identify the effect of different building materials and operational practices on indoor air quality (IAQ) and quantify their impact with respect to its emission and the exposure of the occupants. Further, strategies have been determined to minimize the SBS while developing guidelines to create a healthier built environment. In order to achieve these objectives, concentrations of Carbon Monoxide (CO), Carbon Dioxide (CO2), Nitrogen Dioxide (NO2), Total Volatile Organic Compounds (TVOCs) and Particulate Matter (PM2.5) were measured using Indoor Air Quality Monitor (IQM60 Environmental Monitor V5.0) and Haz-Dust Particulate Air Monitor. A questionnaire survey was conducted to evaluate the satisfaction of the occupants with the indoor environment that they reside and obtain an idea on their reviews to formulate a relationship between the level of comfort and IAQ. At the same time, the effect of the ventilation condition was assessed using the IAQ results of each of these locations. Out of all the building materials and related activities, solvent-based wall paint was selected for the detailed analysis due to the identification of a prominent contribution to the indoor air pollution with its usage. Results from the questionnaire survey were able to justify and present a relationship between the indoor air pollutants and the key symptoms related to SBS. At the same time, ventilation condition has been identified as a key factor that contributes to the betterment of IAQ. A Computational Fluid Dynamic (CFD) model was developed using ANSYS-Fluent software, which was used to predict the TVOCs concentration generated from solvent-based wall paint concerning the ventilation rates under the control of environmental and test conditions. The experimental results were used to validate the CFD model before it is recommended for future references. The validated CFD model could be used to predict the building flush-out period and appropriate ventilation condition to dilute the accumulated pollutants inside the buildings.
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Optimizing passenger movements through airport terminals
Saparamadu, DDGADS; Bandara, JMSJ
Minimizing walking distances, waiting times and delays at critical service centers such as ticket counters, immigration, baggage claim and security checks and optimal spacing of other services or frictions such as shops, washrooms, food cabins and internet accesses within a terminal could contribute much towards passenger comfort. Knowledge regarding arrival and waiting patterns of passengers at mandatory service centers and other services helps model passenger flow through the terminal. This knowledge depends on airport location, the operating strategy of the terminal and the frictions placed in between mandatory service centers. Existing simulation and analytical models for walking distances and waiting times are for specific use at one airport or one part of the airport only. They cannot be used elsewhere. Therefore, finding out flexible mathematical models for common use at all airport terminals is the main purpose of this research. The research concentrates on two main objectives, of which, the first is to develop mathematical models to optimize passenger flow through different servers and other facilities minimizing total waiting time at all mandatory service centers. The other objective is to evaluate the different terminal configurations and find the optimum terminal configuration with the least waiting time for passengers. Data related to waiting time and service time at different mandatory service centers helped find placements for suitable frictions to be located before the mandatory service centers. Criteria developed for the purpose were means and variances of waiting times at mandatory service centers with and without frictions. If the mean waiting time at a mandatory service center without friction is less than that at a mandatory service center with friction, a friction before the mandatory service center gets rejected. Queuing theory helped fix suitable frictions before the mandatory service centers. These analytical solutions were verified using the Monte Carlo simulation using queuing theory. Secondly, proper frictions to be placed before the gates in terminal configurations to minimize passenger delays were realized with the pier type terminal configuration, where the three pier type terminal configurations with frictions was considered for optimal terminal configuration to minimize passenger delays. The optimum terminal configuration to minimize passenger delays appeared to be the terminal with three piers holding an unequal number of gates. The developed models include the common features of all airport terminals and are capable of describing any terminal configuration.
item: Thesis-Full-text
In-situ mud-concrete as a material for load-bearing walls and sustainable building practices
Arooz, FR; Halwatura, R
The world is still struggling to find solutions for the increasing demand for housing with the growing population. To deal with this problem the greater importance has given in researching alternative materials and technologies which can cater sustainable solutions to these evolving demands. However, this materials and technologies must be suitable and appropriate to the local economy, social background and the cultural setting of that country. In the context of innovating sustainable building materials, ‘soil’ receives great attention as an environmental-friendly material, due to its economic affordability, low embodied energy and enhanced natural moisture buffering capacities. Self-compacting Mud-Concrete load-bearing walling (MCW) system is an in-situ cast walling system that combines well-graded soil, cement (stabilizer) and water in their correct proportions. It receives great attention due to its sustainable advantages such as less raw material wastage, low-cost methods, quick construction technology and the low embodied energy consumption. This research presents a detailed analysis of mix design development, system development, thermal performances, long-term performance and cost-effectiveness of self-compacting Mud-Concrete load-bearing walls (MCW). Results demonstrate that optimum usable gravel range is 4.75-32mm in MCW technology. Further, the mix design was finalized as fine - 5% (≤ sieve size 0.425mm), sand - 50 % (sieve size 0.425mm ≤ sand ≤4.75 mm) and gravel - 45% (sieve size 4.75mm ≤ gravel≤ 32mm) with 4% minimum cement of the total dry mix. In addition, optimum 20% of water can use to keep the self-compacting quality of the mix. Grading curves were developed constantly at 4%, 6%, 8% and 10% cement produced the best mix design with standardized methods. Also, the methods were introduced to predict the exact strength of MCW prior to construction. Accelerated erosion tests were conducted to determine the durability of MCW cast of the best mix design and the results satisfied the standard durability requirements under SLS1283. In addition, MCW can be listed as one of the excellent moisture buffering materials according to NORDEST classification system. Optimum lifting height of a wall segment was found as 1200mm which can cast at once without proposing any joints. In every 1200mm height, the proper horizontal joint should be introduced in in-situ cast process and the introduced joint should keep the maximum continuity in between the wall segments. In addition, the results show maximum horizontal shrinkage is 0.23% and maximum vertical shrinkage is 0.22% within 07 days of curing period. Increasing the curing period from 07 days to 14 days, the shrinkage strain was reduced from 0.23% to 0.15%. It depicts that shrinkage strain can reduce in 65% by increasing the curing period for 14 days. Thus 14 days proper curing procedure was recommended to in-situ cast MC wall and the curing should start soon after dismantling the formwork of the wall segments. MCW has 1.2 W/m.K of conductivity, 1440 J/kg.K of specific heat capacity, 1540 kg/m2 of density, 0.366 m2.K/W of R-value and 2.17 W/m2.K of U-Value. MCW acts as a good thermally resistive material due to its thermal mass and insulation characters. Comparatively, MCW has a low embodied energy and life-cycle cost due to the less material wastage, high reusability, fewer labour consumption and quick in-situ construction technologies. Ultimately the research invented a self-compacting in-situ cast load-bearing walling system through Mud-Concrete, which can highly cater to sustainable demands in the construction industry.
item: Thesis-Full-text
Development of a sustainable energy rating system for residential buildings in Sri Lanka
Pathirana, SM; Halwathura, R; Rodrogo, A
Energy rating system can be considered as a key policy instrument that will assist the government to reduce energy consumption. Energy rating includes the direct bene ts such as, energy requirement and carbon dioxide emission reduction, cost reduction for the users, increase the public awareness regarding energy issues, and improve the availability of information regarding the building. The government of Sri Lanka also has identi ed the importance of energy performance of buildings and considers it as a strategy for the sustainable energy development of the country. Existing rating systems in the world only considered limited factors related to energy consumption and to provide more accurate rating system it is proposed that a more sustainable energy rating system should be developed considering all the criteria. This research is aimed at identifying the existing rating systems, investigate the existing systems, to identify the parameters required for determining the energy performance of residential buildings, to develop and equation for calculating the energy score and to develop a scale for comparing the energy performance of residential buildings in hot and humid climate in Sri Lanka. To achieve the above mentioned objectives, this research followed the concept of sustainable energy which comprises of both energy e ciency and renewable energy. The energy e ciency of a residential building needs to consider the energy e ciency due to building properties and energy e ciency of the occupants. To evaluate the energy e ciency of the building properties, the asset rating method was used where the building is modeled and the energy consumption for thermal comfort and lighting is calculated. Using 4569 di erent models (varying window to wall ratio, orientation, zone size, zone location, building shape and oor area), a parametric analysis was conducted to develop an optimum model which was then used as the reference value for the rst sub rating (Building consumption rate). A questionnaire survey was conducted to identify the factors a ecting the energy consumption of the Sri Lankan residential buildings and in total 336 lled questionnaires were used for parametric analysis. The questionnaire revealed that the number of bedrooms is not signi cant for energy consumption and the occupant characteristics and the equipment usage are highly signi cant factors. Therefore, when developing the occupancy behaviour rate, the average domestic energy consumption in Sri Lanka was used as reference, without normalising. To consider the renewable energy usage, another sub rating named energy source rate was developed and to decide whether to o set the energy consumption with renewable energy use or to use a separate index, another questionnaire survey was conducted with rooftop solar PV consumers. The results of the survey indicated ii that there is a strong rebound e ect due to the solar PV adoption and there are some other social and technical impacts as well. Therefore, when developing the energy source rate, a sustainability index was used and based on the percentage of contribution of the energy sources to the nal energy use the nal energy source rate was determined. These three sub ratings were normalised and brought to a common scale of 0 to 100. The sub ratings were integrated using weightages which were obtained using a perception survey of engineers, architects, quantity surveyors and facility managers in the industry. The application of the rating method is explained using two actual examples. Further, a sensitivity analysis was done to re ect the e ect of the changes in the parameters used in the score calculation equation using the rst sample house. The rating methodology proposed in this thesis can be used over any country or any building by changing the reference values and weightages. Keywords: Energy rating; energy e ciency; buildings; thermal comfort; renewable energy; energy labels; consumer behaviour