Master of Philosophy (M.Phil.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/18720

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item: Thesis-Full-text
Investigating the role of social media platforms in disaster risk communication in Sri Lanka
(2023) Jayathilaka, HADGS; Dr. C. S. A. Siriwardana
Disaster Risk Communication (DRC) is one of the key elements adopted by the global community to reduce the adverse effects of catastrophic disasters. Several drawbacks were identified that caused the ineffectiveness of the DRC in Sri Lanka. One of the significant downsides is the deficiency in proper communication channels for the impactful propagation of disaster-related information. Social media plays a crucial role in developed countries, with previous studies proving its beneficial impact on global disasters. Previous scholars have recognised the possibility of enhancing the efficiency of the DRC in Sri Lanka by utilizing social media. However, there is a lack of proper investigation done based on the exploration of adapting and enhancing social media practice toward the DRC in Sri Lanka. Therefore, the main objective of this study was to identify the existing gaps and barriers by investigating the prevailing use of social media for DRC in Sri Lanka. Through a comprehensive literature investigation, several aspects of using social media during disasters as a communication channel were identified. Consequently, a conceptual framework was developed for utilising social media for Disaster Risk Communication in Sri Lanka. The subsequent section of the study analysed the use of social media in DRC in Sri Lanka based on the critical parameters of that framework. Different data collection methods, such as online questionnaires, telephone surveys, and social media surveys, were used to obtain the required data for the analysis. Besides, various analytical techniques were used to conduct the analysis. Several conclusions were drawn from the analysis results, which provide numerous suggestions for bridging the gaps and barriers identified from the analysis. The outcomes of this study will help in enhancing social media usage for Disaster Risk Communication in Sri Lanka. Keywords: Disasters, Disaster Risk Reduction, Disaster Risk Management, Disaster Risk Communication, Social Media
item: Thesis-Full-text
Decision making model to enhance knowledge on climate change, sustainable design and energy conservation
(2023) Gunawardana SAA; Halwatura RU; Tupenaite L; Arooz R
Incorporating sustainability into university education enhances the knowledge of the students to practice sustainability concepts in their professional life.This research was conducted to determine how the university curricular-based education on three parameters, i.e. climate change, sustainable design, and energy conservation (CC, SD & EC), influences the individual’s factors and cognitive variables by developing decision-making models. Two complementary surveys were conducted; one for university students and another one for university lecturers. In the study conducted for university lecturers, a sample of 352 in the universities of Sri Lanka were considered. Their perceptions, current curricular contribution, their identification of issues and improvements, and their future intention to incorporate in curricula related to three parameters, i.e. CC, SD & EC were identified and their interactions were analyzed. Similarly, the influence of educational fields and social interactions on the considered variables were examined. The second study aimed at university students which comprised a sample of 586 from the universities of Sri Lanka and Russia. Cognitive variables such as Perceptions and personal factors such as Personal Interest and behavioral aspects related to three parameters, i.e. CC, SD & EC were analyzed. The influence of the university curriculum on the considered variables was examined. The data were statistically analyzed using SPSS version 25 and models were developed using Structural Equation modelling (SEM) conducted via IBM AMOS version 23. Developed models were validated through the goodness of fit indices. Out of two models, the model developed based on students’ responses was subjected to multi-group analysis to compare variations among Sri Lankan and Russian students in similar contexts. Results of the first study revealed that lecturers' perceptions and current curricular contributions have been influenced by their educational field and their social interactions related to CC, SD & EC. However, their identification of issues and improvements has only been significant with social interactions. The lecturer’s future intention to incorporate in curricula has been significantly influenced by the identification of issues and improvements. Results of the second study in the Sri Lankan context explored variables such as field of study, learning from the university and practical application during the university have not influenced the perceptions of the students towards CC, SD & EC. However, their Personal Interest (which is a personal factor) has influenced their perceptions towards CC, SD & EC. Furthermore, it was determined that some of the positive perceptions towards CC, SD & EC have influenced the positive behavior of the students towards CC, SD & EC. Russian students’ responses revealed that their perceptions on CC, SD & EC have been significantly influenced by their practical application, the field of study, and personal interest. However, learning from the university has not influenced their perceptions. Similarly, it was also identified that their positive perceptions are not necessarily depicted from their respective behavior related to CC, SD & EC. Furthermore, the goodness of fit indices validated and confirmed the reliability of the developed models. Overall, it was determined that universities as centers that generate knowledge, should try to fill the gap between objective knowledge and subjective knowledge, and therefore, it will permit students to make better-grounded decisions and also enhance their perceptions
item: Thesis-Full-text
Quantitative approach to hospital resilience based on system dynamics : case of Sri Lanka
(2023) Jayasekara JHPRU; Siriwardana CSA
Past records depict that both the intensity and frequency of climatic-related hazards are increasing devastatingly. Although the number of deaths caused by these extreme events has been comparatively less recently, the economic losses have increased considerably. The complexity of the world with interconnected infrastructure systems has been the main catalyst of these huge losses. COVID-19 and concurrent hazards have set out a perfect example that shows hazards no longer affect discreet parts of the system but render the failure of the whole system. Out of critical infrastructure sectors, damages on health systems have attracted global concern more as the impacts on the health sector can cascade further to socio-economic aspects as well. Therefore, currently, health is considered an important part of disaster risk reduction. Sri Lanka, as a tropical country, experiences climatic-related hazards more frequently. Although Sri Lanka has a disaster management mechanism and public health system, a limited number of evidence exists on integrated systemic risk management mechanisms in the country. Most of the existing emergency and disaster management mechanisms have a hazard-by-hazard approach and fail to incorporate synergized impacts of compound hazard events. The levels of integration of public health and disaster risk management aspects into each other still needs to be enhanced. In a context where systems thinking approaches are more promoted in disaster resilience, this study aims at providing a framework for assessing the public health system disaster resilience for multi-hazard contexts amidst biological hazards. In this regard, this study has followed multiple steps to evaluate the existing health disaster management approaches in the country. Initially, a desk study was conducted to identify key drivers of effective response mechanisms for pandemics, which can affect the capacities of integrated disaster risk management approaches. It was followed by a stakeholder analysis, which used Social Network Analysis (SNA) to identify the stakeholder behaviour in the country for multi-hazard preparedness planning. Furthermore, field data collection was conducted under three phases, including forty-one key informants representing the sectors that are related to disaster management in the country. Qualitative information from this step was analysed using systems thinking and cascading effects were modelled for early warnings, evacuation, shelter management, and hospital functionality. Since functional continuity of healthcare facilities was identified as a key driver of multi-hazard preparedness and response mechanisms, this study presents a model that captures interdependencies within a hospital during a hybrid hazard scenario. As the final outcome, the study presents a framework for enhancing public health systems resilience for multi-hazard contexts. The developed framework was tested for its applicability at the community level in Sri Lanka, through scenario workshops. Along with these outcomes, the study further presents a set of gaps that needs to be immediately addressed based on lessons from recent multi-hazard scenarios amidst the COVID-19 outbreak in Sri Lanka
item: Thesis-Abstract
Development of a methodology to evaluate safety performance in low volume roads
(2022) Ranawaka RKTK; Pasindu HR
Road safety is a vital element of the road's overall function, which is often neglected in decision-making for road maintenance management. As a result, the safety issues, especially in rural roads, remain without funding to implement the necessary countermeasures. One constraint faced by local authorities is the lack of analysis tools to select appropriate safety treatments within the available budget. Low-volume roads provide connectivity between residential/commercial areas and the national road network. They are especially critical in rural areas to provide accessibility to the community for social and economic needs. Low volume roads account for nearly 61% of the road network length in Sri Lanka. With the rapid motorization taking place in Sri Lanka, it is expected that traffic on these roads will increase significantly in the future. However, some of these roads have not been developed according to the standard design guidelines and raise major safety issues on such roads as a result. Considering the expected growth in traffic and prevailing issues concerning roadway design, the safety level decrease in these roads raises risk to the road user. Therefore, it is essential to evaluate the safety performance of low volume roads. Existing safety evaluation methodologies rely on traffic data, and accident statistics, which may not be readily available for the low volume road network. Therefore, it is necessary to develop a non-subjective methodology to evaluate the safety performance of low-volume roads, considering the data limitations present in developing countries. This study analyses the main casual factors of low volume road accidents and a novel approach, i.e., Cumulative Safety Index: CSI, designed to evaluate the safety performance of low volume roads considering the data limitations present in developing countries. This study also proposes a methodology to incorporate road safety performance in rural roads in maintenance planning using a multi-objective optimization approach. Road safety performance is defined in terms of the CSI, which is computed based on the severity, exposure, frequency of safety issues that road safety audits have identified. The safety performance and pavement condition-related indices, such as International Roughness Index: IRI, pothole number, etc., are included in the Multi-Objective Optimization: MOO decision criteria analysis. It comprises two objectives: minimize network IRI, and minimize network CSI. Applicability of the developed model has been demonstrated from the illustrative example of a rural road network. Results have shown that roads with safetyissues can also be prioritized in budget allocation while ensuring the network-level pavement condition can be maintained at a reasonable level. This methodology offers a simplified approach to incorporate road safety issues in rural road maintenance planning. This study presents a methodology to logically determine the safety treatment criteria for a selected road to increase the safety performance at the project level. The safety treatments are taken based on a linear programming model that optimizes the safety performance of the selected road. CSI represents the safety performance of the road, which is determined based on the prevailing issues on that road. The model comprises the objective function that maximizes the safety performance of the selected road concerning the number of prevailing safety issue types. This model is used to identify the optimal safety treatment scheme for the road chosen, ensuring prevailing road safety issues are effectively addressed. The objective function consists of the Initial CSI of the selected road and the safety improvement after treating relevant issue type coupled with a binary decision variable.
item: Thesis-Abstract
Stabilization of soil with plastic waste and leaf ash
(2022) Yathushan V; Puswewala UGA
This study aims to investigate the stabilization of three sandy soils with the addition of waste plastics, Bamboo Leaf ash (BLA), Banana Leaf ash (BALA) and a leaf ash mixture based on the enhancement in the MDD (Maximum Dry Density), OMC (Optimum Moisture Content), Soaked CBR (California Bearing Ratio), Shear strength parameters and Atterberg Limits. The soil stabilizers used in the study are the plastics strips from waste plastic file folders, BALA, BLA and a pozzolanic leaf ash mixture of five commonly available pozzolanic leaves in Sri Lanka. Plastics used in the study have 5 mm width and Aspect Ratios (ARs) of 1, 2, 3, and 4 in the weight percentages 0.5, 1, 2, 4, and 8. BALA, BLA and the leaf ash mixture used in the study are in the weight percentages 2, 4, 6, 8, and 10. The most significant improvement in MDD was achieved when 2 % of plastics with an AR 02 was mixed with soil 01. For soil 02, the best improvements in MDD with almost similar values were observed with the addition of 6 % of all the considered ashes. For soil 03, the best improvements in MDD with almost similar values were achieved with the addition of 6 % of BLA and the leaf ash mixture. The optimum improvement in soaked CBR for each soil was around (2-3) times compared to the virgin state. The optimum improvement in soaked CBR was observed with the addition of 6 % of BLA for all three soils. Shear strength parameters improved in almost all cases of the addition of plastics and ashes. A reduction of plasticity index (PI) was noted on all three soils with the addition of 2, 4 and 6 % of ashes. Soil 03 mixed with 2 % plastics of AR 03, 8 % BALA, 6 % BLA and 6 % mixture of pozzolanic ashes showed satisfactory results to be used for the upper subbase layer in flexible pavement constructions in Sri Lanka.
item: Thesis-Abstract
Investigation on the applicability of bottom ash for restoration of clay mines in Sri Lanka
(2021) Suloshini S; Ranathunga AS; Kulathilaka SAS; Gunawardana WB
The higher cost associated with the restoration of clay mines and shortage of suitable filling materials have created many abandoned clay mines in Sri Lanka, leading to various environmental and health issues. Bottom ash (BA) generated during the coal combustion process as a by-product is one such potential fill material. Therefore, utilizing BA as a full or partial replacement of soil during clay mine restoration is the main objective of this study which was fulfilled under four sub-objectives: 1) potential as a backfill material, 2) ability to prevent soil erosion, 3) potential as a soil amendment material and 4) environmental impact. BA was collected from the Lakvijaya power plant in Norochcholai, Sri Lanka. In addition, the suitability of BA as a full or partial replacement for soil was tested with six different fractions of BA (0%, 50%, 60%, 75%, 90% &100%) using a gravelly lateritic soil. The basic properties, shear strength parameters and compressibility characteristics of BA-soil mixtures were investigated. Annual soil loss due to rainfall was measured by conducting artificial rainfall tests for BA-soil mixtures. In addition, chemical composition, pH, electrical conductivity, water holding capacity and micro-structural morphology through Scanning Electron Microscope of BA-soil mixtures were determined to evaluate the potential of soil amendment capabilities. Furthermore, column leaching method was used to evaluate the trace metal concentrations of BA-soil mixtures. According to results, BA behaves as a poorly graded sand, a free draining material with low compressibility and cohesion. BA has a lower maximum dry density (975 kg/m ) and higher optimum moisture content (37%). The annual soil loss is “very low” when the fine fraction of the BA-soil mixture is lesser than 20%. BA has the potential to improve agronomic characteristics of soil due to the better water holding capacity and electrical conductivity. BA can adjust soil pH to a desirable plant growth range. Interestingly, the micropore structure of BA has a positive influence on compressibility characteristics, soil erodibility and plant growth while compaction characteristics are influenced negatively. According to column leaching test results, the leachability potential of trace metals in BA does not exceed the allowable limits. Finally, an empirical relationship for the compaction characteristics was developed using multiple regression analysis with a prediction accuracy less than ±3%. Further, the specific gravity of BA was predicted using the chemical composition by soft computing techniques with an accuracy around 96%. The proposed models could be used for the preliminary assessment of the suitability of BA prior to a project. By considering the results and economic benefits, it can be concluded that, utilizing BA as a partial replacement of a traditional fill material (up to 75%) is the most suitable combination for restoration of abandoned clay mines and similar applications according to the present study.
item: Thesis-Abstract
A Framework for critical infrastructure management with the focus on disasters : case study approach
(2021) Shehara PL A I; Siriwardana CSA
The significance of Critical Infrastructure and the important focus to enhance their level of resilience capacity is defined by the Sendai Framework for Disaster Risk Reduction developed for 2015-2030. Furthermore, Goal 9 defined by the Sustainable Development Goals calls for creating resilient infrastructure and enhancing their capacity level. Accordingly, the resilience enhancement of the Critical Infrastructure can be delivered by elements of Multi-Hazard Early Warning, which is a strategical concept of Disaster Risk Reduction mechanism. This strategical integration to resilience enhancement can be more effective with the novel technological implementation of Early Warning dissemination. In the research study, main concern is towards development of a strategical resilience assessment framework for Critical Infrastructure management in Sri Lanka. Along the focused research scope, the Transportation Infrastructure sector was focused on framework development. Transportation sector has a wide concern in which their performance on operation depends highly on the level of capability of adapting and recovering from a disaster incident. From the global level developed frameworks, the Australian Critical Infrastructure Resilience Strategy was identified as the basis for the resilience framework development. Based on this framework the integration of community, organizational and technical infrastructure resilience aspects were identified as the key basis. From the initial literature review, the parameter identification was undertaken and initial parameter selection was undertaken. Here, the community resilience aspects were determined through field survey in which overall 393 responses were collected. The organizational resilience aspects were determined through telephone interviewing in which 1004 responses were collected. The technical infrastructure resilience aspects were determined using field studies and focus group meetings. The identified parameter from the literature review and the initial literature survey was categorized and filtered under the expert opinion survey. For the quantification of the resilience capacity, the quantification of each of indicator aspects were considered. Here, the Analytical Hierarchical Process was applied to capture the weights for the each identified parameter through expertise determination. Through this, the relationships among each variable aspects were considered for the determination of resilience level. With this, the applicability was determined using a case study in Amaragedara South Grama Niladari division in Bulathsinhala Divisional Secretariat division. The key summary output of the framework implication in regional level aspects can be incorporated into the planning stage of the Disaster Management system in the country.
item: Thesis-Abstract
The Effect of terrain data resolution on flood modelling - a study in downstream of Kelani river basin, Sri Lanka
(2021) Suja ACA; Rajapakse RLHL
Frequent severe flooding in Colombo due to the overflow of the Kelani River emphasizes the necessity of flood modelling as inundation extents and flood depth can easily be identified for implementing effective flood control measures. The accuracy of flood modelling is primarily influenced by topographical data sources and their data resolution. Due to the unavailability of surveyed or Light Detection and Ranging (LiDAR) datasets in most regions of Sri Lanka, the accuracy and applicability of alternative topographical datasets need to be studied. The different topographical data sources, namely Shuttle Radar Topography Mission (SRTM) with 30 m and 90 m resolution, Advanced Spaceborne Thermal Emission (ASTER) with 30 m and 90 m resolution and 1:50,000 topographical map were chosen for this study. The 1 m resolution LiDAR dataset was used as a reference dataset to assess the accuracy of aforesaid datasets and was resampled to 30 m and 90 m to investigate the effect of resolution with the aforementioned datasets. This study was carried out downstream of Kelani River basin, Sri Lanka from Hanwella to Colombo, covering an area of 250 km2. The 2-D hydraulic modelling was carried out using Internation River Interface Cooperative (iRIC), public domain software and Arc-GIS was used to carry out most of the analyses. The results of the terrain attribute indicate that 1:50,000 topographical map has shown the complete erroneous elevation and slope variation: 70% of the area shows the constant elevation value of 20 m; 20% of the area shows the constant elevation value of 10 m; 93% of area shows as flat terrain (zero slopes). Therefore, 1:50,000 topographical map was not considered for further analysis and the rest of the datasets were considered. Moreover, results show that the accuracy of mean elevation variation is significantly affected by topographical data source rather than their data resolution. Nevertheless, slope variation is significantly affected by their data resolution rather than the topographical data source. Flood events that occurred in May 2017 and May 2018 were used for calibrating and validating the model. The model developed in the study performed well in calibration and validation in terms of three objective functions, namely Percentage Bias (PBIAS), Nash-Sutcliffe and Mean Relative Absolute Error (MRAE). The values of PBIAS were 5.61% and 8.56%, Nash-Sutcliffe were 0.80 and 0.55, and MRAE were 0.11 and 0.13, for calibration and validation, respectively. The accuracy of developed models was assessed with respect to the reference dataset in terms of two primary hydraulic contexts, namely flood depth and inundation extents. The results show that reduction in the resolution of LiDAR digital elevation model (DEM) does not significantly affect the model accuracy as even 90 m resolution LiDAR DEM produced higher accurate results (flood depth, root mean square error of 0.95 m; inundation extent, F-statistic of 70.21%) than the 30 m resolution SRTM and ASTER DEMs. Moreover, the 90 m resolution ASTER DEM produced the least accurate results in terms of both flood depth and inundation extents. The method was developed to correct the SRTM DEM (30 m resolution) to improve the accuracy using high-resolution LiDAR elevation points. The results indicate that the accuracy of both hydraulic outputs produced by corrected SRTM DEM improved (flood depth, root mean square error of 0.91 m; inundation extents, F-statistic of 80.06%). Moreover, no correlations were found between errors and land use, and errors and terrain attributes. The proposed method may be applied in the areas where high-resolution LiDAR data are not available using surveyed elevation data
item: Thesis-Abstract
A Methodology to estimate the changes in trip distribution due to the land use changes according to the modified traffic analysis zones
(2021) Weerasinghe WMCO; Bandara JMSJ
Land use and transportation have a significant impact on each other, therefore planers, engineers, decision makers and scholars have researched on the interaction between land use and transportation over the past few decades. This research leads to capture the complex inter dependency of transportation and land use on each other in an urban context. Even though there are several land use-transport interaction models in both micro level and macro level, there is a necessity to address the intermediate level zoning system to capture both link capacity and junction capacity, as well as the land use, socio-economic characteristics and the traffic flow. Moreover, except considering traditional administrative zones and cell-based analysis to estimate the trip distribution, the traffic analysis zones have to be re-demarcated to address the real ground situations. Additionally, this research describes a methodology to distribute macro level trip origin-destination (O-D) data into much smaller level zones considering the land use character of the area. The objectives of the research are, to develop a methodology to demarcate traffic analysis zoning system applicable to local level transport modelling in urban area, to develop a methodology to estimate the trip generation in local area based on the available land use information and to develop a methodology to estimate the passenger flows on links based on the Modified Traffic Analysis Zone. Further, this research provides a guidance on land use and transportation decision making. The methodology is developed based on both spatial and statistical analysis using several software and tools. The study area of the research is the Colombo Municipal Council area, which is located within Colombo District, Western Province, Sri Lanka. The necessary data are collected from secondary sources from relevant departments and authorities in Sri Lanka.
item: Thesis-Abstract
Development of a demand model for school trips in Colombo district, Sri Lanka
(2021) Damsara KDP; De Silva GLDI; Sirisoma RMNT
A school trip is defined as a trip that originated from home or a temporary residential location and terminates at an educational institution. According to the ComTrans study, a major portion of the traffic congestion in the Colombo district in the morning peak and afternoon peak are due to the school traffic. Understanding the distribution of origindestination patterns of these school trips is important to manage the school traffic. This research targeted developing an origin-destination matrix for the home-to-school trips attracted to the government schools located in the Colombo district. The O-D matrix developed for the study area is further divided into four sub O-D matrices based on the mode of travel as active transportation, public transportation, private transportation and school van/bus services. Further, the research identifies a mathematical model to estimate the number of school trips between origin-destination pairs in the study area using the multiple linear regression techniques. The distribution of home-to-school trips is found to be directly proportional to the number of school-aged children residing in the origin zone, the number of students studying at separate categories of schools at the destination zone while it is inversely proportional to the distance between origin and destination zones and the number of Category I schools (which have classes up to advanced level all streams) at the origin zone. Based on the findings of this research, two mathematical models are developed for inter-zonal school trips and intra-zonal school trips separately. The outcomes of this research can be used for planning transport supply services for school children to fulfil their educational travel needs on a normal day. It may help the authorities to promote active transportation and public transportation among school children as a sustainable mode of travel. The methodology used in this study can be extended to other districts of the country to develop a national-level travel O-D matrix for school trips. Further, the mathematical model proposed in this research can be used for other districts of the country after validating it through a sample trip length frequency distribution diagram.
item: Thesis-Abstract
Development of network level pavement management system for low volume rural roads
(2021) Sandamal RMK; Pasindu HR
In Sri Lanka, there is about 156,000 km length of roads and among those about 92% are considered as rural roads (LVRRs). These roads are playing a pivotal role in community development, transport of people, goods, and services in the rural areas by providing connectivity between residential, agricultural areas and the national road network. In the future, with rapid motorization takes place, it is expected the traffic volume on these roads will increase significantly. Limited funding, subjective and ad-hoc maintenance decision making has resulted in suboptimal maintenance level for these road networks. Moreover, the inability to collect extensive data which are needed to run most of the existing pavement management systems (PMSs) and the technical expertise required has resulted in the low usage of such systems by local road agencies. Therefore, there is a need to develop a cost-effective simplified approach for network-level decision-making to assist in pavement maintenance management. The study explored the applicability of smartphone-based roughness data to assess the pavement condition of LVRRs as a novel pavement performance evaluating criteria by validating its accuracy compared with a Class III type roughness measurement equipment. The correlation value between the two measurements was high as 0.84. Even though, the relationship has shown that smartphone roughness slightly underestimates road roughness still it can apply to LVRRs as a cost-effective, accurate method. Moreover, it was assessed whether roughness results represent pavement distress conditions in the LVRRs. Regression models were developed to find the relationship between International Roughness Index (IRI) and key distress types. It was found that Raveling, Edge Breaking, Pothole, Edge Breaking, Edge Gap has shown a good correlation with IRI as 0.61, 0.56, 0.55, 0.52 respectively. Further, to evaluate the combined effect of distress on IRI progression, stepwise multiple regression analysis was conducted by considering the roadway width and the model for narrow roads had an R-squared of 0.89. For the wider roads the model accuracy is high as with R-squared of 0.86. Interestingly, pothole was identified as the key distress type in both models while edge breaking and edge gap only relevant in narrow roads. Finally, IRI progression was evaluated with the Pavement Condition Index (PCI) and a non-linear relationship was found with an Rsquared of 0.75 from the sigmoidal function. Moreover, relationship between IRI with Pavement Serviceability Rating (PSR) was evaluated and found that a good relationship with R-squared of 0.76 for the model. The relevant maintenance strategies used for LVRRs were identified by establishing threshold and trigger values based on the works of literature and current practice in the Sri Lankan context. To support the decision-making criteria, an analysis scheme was developed by using a defined decision tree. The objective function was established as the minimization of the average network IRI value which represents the maximum network condition. Two analysis systems were developed; one with Integer Programming and the other with a Genetic Algorithm (GA) based system. In addition to that, Engineer’s judgment was compared with the two methods by using an illustrative example. From the results, it was found that GA is always provided the optimum work program while Integer Programming merged into a suboptimal level. Although Engineer’s objective decision-making has shown significant variation when there is a budgetary constraint. However, when there is a sufficient amount of budget available most of the Engineer’s judgments were also close to the optimum solution. Further, in this study socio-economic importance was incorporated in the maintenance planning decision-making scheme by using the multi-objective optimization analysis. A socioeconomic priority index was developed by using the priority factors namely traffic volume, land use, community importance & accessibility to the road network. In there, a network-level maintenance strategy budget estimation tool will also be introduced by considering different road surface conditions and maintenance strategies used in LVRRs. The set of optimal solutions for the multi-objective problem generated using the ‘Pareto Optimality’ concept. A case study was performed and found that the method would be useful in prioritizing the roads having socio-economic importance. Furthermore, another illustrative example was performed by incorporating safety performance in decision criteria using a predefined parameter called Cumulative Safety Index (CSI). The study has also shown that rather than spending money on optimizing a single objective, optimization of multiple objectives at a time would be a better option since the improvement of the existing network is higher in that case. Moreover, the multi-objective optimization approach would provide ability to include objective functions which cannot be incorporated in single objective optimization approach. The core attributes of the proposed system are, reduced the data requirements, simplified the analytical tools and allowing users to customize considering the resource constraints in prioritization and optimization and that would allow road agencies to make objective decisions and optimize the road maintenance process. The finding from this research can be used for maintenance planning for local road authorities in Sri Lanka as well as for other developing countries by adopting the parameter defining for their local context.
item: Thesis-Abstract
Assessment of structural vulnerability of Sri Lankan hospitals under natural hazards – Tsunami as a case study
(2021) Hasalanka HHH; Siriwardana CSA; Mallikarachchi HMYC
Hospitals are considered critical service units of a society that need to operate before, during, and after disasters. The Ministry of Health of Sri Lanka has embraced the “Safe Hospitals” Initiative promoted by the World Health Organization (WHO), as a strategic priority for health sector Disaster Management to strengthen the resilience of the hospitals. WHO has developed a toolkit for the assessment of the safety of hospitals including structural, non-structural, and functional aspects. This toolkit consists of four modules that are; hazard identification, structural safety, non – structural safety, and emergency and disaster management. A review of this toolkit has pointed out the need for major alterations to the structural safety module of the Safe Hospital Toolkit to Sri Lanka since the Sri Lankan disaster profile is quite different from that of the Latin American countries in which the toolkit was developed; where earthquakes and cyclones are predominate. The objective of this assessment was to develop a toolkit to assess the structural safety of hospitals in Sri Lanka addressing the structural vulnerability/robustness of buildings considering natural hazards; high winds, floods, tsunamis, and landslides. Accordingly, a draft Structural Safety of Hospitals assessment Sri Lanka (draft SSH – SL) has been developed based on the Safe Hospital Toolkit and the available Sri Lankan guidelines for hazard resilient constructions. Then, the draft SSH – SL has been used in a pilot study to identify its limitations, on two hospitals based on their functionality, namely the District General Hospital Gampaha and the Teaching Hospital, Kegalle. To further develop the SSH - SL, field data of another pilot study conducted on six hospitals on the southern coast are used along with a thorough literature review. Moreover, expert surveys were conducted to further improve the toolkit and to obtain the weights using the Analytical Hierarchy Process (AHP), for all the criteria in the SSH – SL, and a Structural Robustness Index (SRI) is defined. Finally, the developed tool under tsunamis is checked for applicability based on the data obtained from the second pilot study and is validated by comparing the actual damage occurred in 2004 Indian Ocean Tsunami with the obtained SRI scores. However, the developed tool for other assessments require validation through more case studies. According to the relative weights obtained through AHP, two main attributes; construction material and the foundation system were found to be significantly important. The assessments of tsunamis and floods share the same building attributes with different weights; the attributes of the lateral load resisting system and the number of stories get a higher weight under the tsunamis compared to floods, as the impact loads applied by the tsunamis are higher than that of the floods. Considering the SRI scores, it was found that the median score for the general assessment is 3 whereas it is 2.33 for all the other assessments. This gives a clear idea of the robustness of buildings as the SRIs above the median score are tend to be robust and the SRIs below the median tend to be vulnerable. The case study carried out focussing on the assessment developed for tsunamis suggests that the Structural Robustness Index (SRI) method is a more nuanced and improved method for assessing the structural robustness compared to the PTVA method. It is highlighted that the SRI method identifies structures that are above the median level in terms of structural robustness than that of the PTVA method. As far as the intra-hospital variation is concerned, the SRI variation mostly depends on the building attributes such as the number of storeys and the construction material. It is also identified that there is a coupling effect between building attributes such as the construction material and the number of storeys as the buildings with a higher number of storeys are also tend to be made of reinforced concrete frames whereas the single storey buildings are made of masonry. The inter-hospital variation of SRIs mostly depends on the surrounding attributes as they change with the geographical location. These results are valid for the buildings up to four storeys including unreinforced masonry, reinforced concrete structures with masonry infills, and reinforced concrete framed structures that were assessed during the field survey. The SSH - SL could be further improved by incorporating the level of exposure and functional attributes and emergency and disaster management attributes to develop a comprehensive risk index, which is beneficial for the disaster management decision-making stage of hospitals.
item: Thesis-Full-text
Study on the performance of CFRP strengthened corroded steel members
(2020) Perera UND; Gamage JCPH
Most of the metallic structures such as offshore platforms and railway bridges are now in the need of retrofitting due to corrosion. One of the efficient ways of strengthening these structures is by using (Carbon Fibre Reinforced Polymer) CFRP materials. Since the weakest link in this system is the bond between the adherends, the effect of pre-corrosion level of the steel elements on the bond characteristics and durability performance of the strengthened units should be properly evaluated. Even though there are many research studies on bond durability none of them has used corroded steel plates for bond strength evaluation and considered the inherent surface characteristics of the corroded steel surfaces. Therefore, this study aimed at investigating the bond performance of CFRP bonded corroded steel plates which are subjected to different ageing conditions and surface roughness characteristics. A total of one hundred and twenty-eight conditioned and non-conditioned double strap joint specimens were tested. Both corroded and non-corroded steel plates and two different surface preparation methods were used to witness the importance of the surface texture properties. Scanning Electronic Microscopic (SEM) analysis was carried out to determine the surface characteristic properties of the corroded/non-corroded steel plates. The short-term bond performance was evaluated along with different bonding configurations. In the long-term analysis, six different environmental exposures; seawater, wet/dry cycles, open tropical environment, and distilled water at three different temperature levels, 25 o C -30 C and 3 o C were considered for conditioning. Residual bond strengths of the conditioned test specimens were evaluated after 6- and 12-month exposure periods at ambient temperature. A numerical model was developed to estimate the stress-strain variation of CFRP/steel specimens along the bond line. Bond-slip curves were evaluated to estimate the interfacial fracture energy of CFRP/steel composites. Moreover, experimental results were compared with the analytical results obtained from Hart-Smith model and a theoretical relationship between the failure modes was derived. Test results indicated a major influence of surface roughness on the long-term performance of CFRP/steel joints. CFRP strengthened corroded steel joints showed a residual bond capacity of about 90% in seawater immersion and 111% in tropical environmental condition suggesting its suitability to adopt CFRP technique in these exposures. After 12 months of exposure duration, a similar bond degradation was observed of about 31% in distilled water immersed specimens at ambient temperature and about 60% in dry/wet cyclic condition irrespective of the pre-corrosion level. During an exposure period of 12 months, the rate of bond degradation was found to be less than 20% for cold water immersed specimens with non-corroded steel plates. The interfacial fracture energy of CFRP/steel composites exposed to hot humid environments indicated a significant reduction of 78% compared to control test specimens.
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Numerical Modelling and experimental investigation on enhancing punching shear capacity using carbon fiber reinforced polymer on flat slabs
(2020) Silva MAL; Gamage JCPH
Flat slabs are much vulnerable to shear failures because stress transferring between the column and the slab happens within a considerable small region. This creates high stress at the slab-column connection area result in punching shear failure. Shear failures are a little different from other failure modes such as flexural failure and excessive deflections because it shows a sudden nature while failing the member. Therefore, giving adequate shear capacity for the flat slabs is crucial. Carbon Fiber Reinforced Polymers (CFRP) is a new material which can be used for structural strengthening. Use of CFRP is promoted by its competitive advantages such as high strength and stiffness to weight ratio, corrosion resistance, low thermal expansion, non-magnetic properties, good fatigue properties and ease of handling. The sudden punching shear failure tendency of flat slabs is a critical issue. Installation of CFRP flexural reinforcements and post installed CFRP shear reinforcements to enhance punching shear capacity are successful approaches. In this study, medium scale flat slab panels were prepared and strengthened with CFRP. Effects of seven alternative bonding arrangements of CFRP were studied. More than 120% punching shear gain was noted from the specimens strengthened with the combination of CFRP flexural and shear reinforcements. Further, the effects from end anchorage of external CFRP and the refilling material at drilled locations to install CFRP shear strengthening scheme were investigated in terms of the enhancement on punching shear performance. A numerical investigation was also conducted to analyze bond behavior and stress behavior. The model predicted performances are in good agreement with the test results. A parametric study was also performed. The use of double-layered CFRP as external reinforcement was found to be the most effective multi-layered system. Further, the identification of the critical locations for the application of the external CFRP strengthening scheme was determined and the practical importance of providing end anchorage was quantified.
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Development of a model to evaluate capacity of urban multi-lane roads under heterogeneous traffic conditions
(2020) Jayaratne DND; Pasindu HR
Road capacity is defined as the maximum sustainable hourly flow rate at which vehicles can reasonably be expected to traverse a point or uniform section of a lane during a given time period under prevailing roadway and traffic conditions in the US Highway Capacity Manual. The knowledge of capacity of a given section of a road is an important input parameter for transport planning and traffic management studies. Presently, there aren’t any up-to-date guidelines for road capacity estimation in Sri Lanka. The use of foreign guidelines is not recommended as each country has unique factors that influence capacity. Since urban multi-lane roads are typically the busiest roads, this research study focuses on developing a capacity estimation model for urban multi-lane roads in Sri Lanka. Flow and speed data were collected using manual counting methods and Google Distance Matrix API (Application Program Interface) method respectively. The heterogeneous traffic flows were converted to Passenger Car Units (PCUs) using Chandra’s method. Greenshields’ traffic flow model was used to calibrate the empirical data. Capacity values were established from the developed flow-speed model. Using this method, the capacity values of all study locations were established. The average observed lane capacity was 1829 pcu/h/l. Regression models were developed to estimate capacity of four-lane and six-lane roads. It was observed that the four-lane road capacity was influenced by the effective lane width, access point density, built environment and median type whereas the six-lane capacity was influenced by the effective lane width and access point density. The four-lane capacity model had an R-squared value of 0.81 and the six-lane capacity model had an R-squared value of 0.86. The two models were combined to create a single model that predicts both 4-lane and 6-lane roads. In addition to the capacity models, a regression model was developed to estimate the Free Flow Speed (FFS) of roads. The predictor variables of the FFS model are lateral clearance, built environment and median type. Verification of developed models were done by surveying 10 road sections. It was observed that all three models accurately predicted flow and speed from the statistical tests done (Mean Absolute Percentage Error <10%). Important findings from the research study includes the development models to estimate four-lane and six-lane capacity values, and FFS. The typical base capacity for a 4-lane urban road was found to be 2044 pcu/h/l. The base capacity for a 6-lane sub-urban road section was estimated to be 2108 pcu/h/l. Even though the capacity values are comparable with capacity values in guidelines such as the HCM (1900-2200 pcu/h/l) since the speeds at capacity are in the range of 20km/h the traffic streams are susceptible to breakdown. The typical FFS of a rural road section with 2m lateral clearance and a center median was 50km/h. Sub-urban and urban road sections with similar conditions have 36km/h and 35km/h FFS speeds respectively. The findings of this research can be used for transport planning and traffic engineering studies in Sri Lanka as well as for further research in the area of capacity estimation.
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An Assessment of wind loading and wind energy potential for Sri Lanka
(2019) Maduranga WLS; Lewangamage CS
It was more than 40 years ago that Sri Lanka last established a wind loading map after the severe cyclone that struck the country in 1978. It is strongly believed that statistical methods had not been used in developing this wind loading map. Hence, the map can either overestimate or underestimate the wind speeds at least in some of the regions of the country. Therefore, an updated map which suits the changing climate patterns experienced in the country has become a necessity. In Sri Lanka, different wind codes are being used when structures are designed to withstand wind actions. Moreover, there is no suitable wind loading map that can be used with the Eurocode 1 or BS 6399-2. The existing wind resource maps for Sri Lanka have been developed in macro scales with low resolutions which is not adequate for effective decision making in wind power generation. Moreover, most of them represents wind speed distributions except for wind power distribution. Therefore, the industry always uses expensive methods to identify the suitable regions for the establishment of wind turbines. As the initial stage of this study a wind loading map for Sri Lanka was developed for different return periods (5, 10, 50, 100, 200, 500 and 1000 years) and for different averaging time periods (3-second gust, 10-minute average and hourly mean) using the wind data obtained from 24 weather stations. The data used were the monthly maximums of 3-minute average and instantaneous maximum wind speeds, recorded over a period of about 35 years. Extreme value distributions called Gringorten and Gumbel methods were tested to predict the extreme wind speeds. Finally, the Gringorten methods was adopted due to its unbiased nature. The generated wind contours for both 3-second gust and 10-minute average basic wind speeds were analyzed for defining the wind loading zones for Sri Lanka. Altogether a new wind power distribution map was proposed for Jaffna Peninsula region in Sri Lanka which has been previously identified as a region with a higher wind energy potential. The required data was obtained from SLSEA (Sri Lanka Sustainable Energy Authority) and the Survey Department of Sri Lanka. Computational Fluid Dynamics based model has been used for the generation of wind power distribution map. The resolution of the map has been increased up to 150 m x 150 m (5” x 5”). Coastal regions such as Veravil, Pooneryn, Ampan, Punkudutivu, Kayts, Kankesanturai, Ponnalli Khadu, Karainagar, Mandaitivu and Alvai were identified as the regions which have the highest wind energy potential in Jaffna Peninsula.
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Basinwide analysis of water resources and pollute transport using a distributed parameter model
(2019) Dahanayake AC; Rajapakse RLHL
The Nachchaduwa sub-catchment (598.74 km2) of the Malwathu Oya basin is seasonally stressed in the dry periods and its downstream parts undergo intermittent floods during monsoon seasons while the fate and behaviour of excess Nitrogen (N) and Phosphorus (P) added to the waterways due to agricultural fertilizers used in the upstream areas remain unresolved. This study incorporated the Water and Energy Transfer Processes (WEP) model to assess the water resources and pollutant transport of the catchment concerning the present status and six possible future scenarios. The required data for the model runs including meteorological, geographical, hydrological, and data related to water quality and anthropogenic activities, were collected and processed identifying the suitable model parameter values. The amounts of N and P in fertilizers applied in this catchment exceeded the actual plant requirement. In both wet and dry seasons, the differences between the measured water quality parameters in upstream and downstream were not statistically significant. The model results of the hydrological component showed that the catchment response to the rainfall was highly regulated due to reservoir storage effect. The model results of the material transport component showed that, on average, the wet season had about 5~7 times the dry season value of the Total Suspended Solids (TSS) in the streams, and in both seasons, the modelled TSS, NO3- and PO43- were within the ranges of the previously published results. Scenario analysis found almost all water quality parameters reduced with the reduction of fertilizer input (maximum 30.64% reduction) and with the increase in temperature (maximum 2.27% reduction), but they increased with the increase in rainfall (maximum 13.49% increase). The findings will be useful in identifying best water resources management practices and coping with the residual N and P in streams and water bodies in a more pragmatic manner.
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Prediction of temperature rise in concrete due to heat of hydration of cement
Mataraarachchi, AIGK; Nanayakkara, SMA
Temperature rise due to heat of hydration in concrete depends on many factors such as geometry of the concrete element, chemical, physical and thermal properties of concrete materials, mix proportion, initial temperature during concrete batching, and thermal boundary conditions during concrete hardening etc. The multicomponent cement hydration model developed by Maekawa et al., predicts the heat generation due to cement hydration based on cement contents, water contents, reference heat generation rate of main mineral components in cement, i.e. alite (C3S), belite (C2S), aluminate (C3A), ferrite (C4AF), and gypsum (CS2H), mineral of cement, fineness of cement, thermal activity and interdependences of mineral components, and effects of consumption of free water during the hydration process etc. This cement hydration model was incorporated in the transient heat conduction analysis. The transient heat conduction analysis was carried out with ANSYS, finite element analysis software using Advance Parametric Design Language (APDL) computer programming to predict the temperature ruse due to heat of hydration of cement in concrete element for a given thermal boundary conditions. Since the heat of hydration of cement is highly temperature dependent, variation of thermal properties of concrete at early ages is essential to predict the temperature response due to heat of hydration of cement in concrete. Experimental investigations were carried out to develop a model to estimate the variation of thermal conductivity of concrete from fresh to hardened state. The specific heat capacity of concrete (ϲ) was estimated based on the specific heat capacities of cement powder and hydration products using Dulong – Petit Rule (DPR), Neumann – Kopp Rule (NKR), and mixing theory. Thermal conductivity of concrete (λ) was determined by fitting temperature rise curve at center of cube with temperature rise curve predicted by transient heat conduction analysis. Estimated specific heat capacity of concrete was applied in iv transient heat conduction analysis program, to predict temperature rise curve from 1hrs to 1day for several mix proportions. A mathematical model was developed to predict the variation of thermal conductivity based on experimentally investigated thermal conductivity data, mix proportions, thermal conductivity of concrete material found in literature, cement and water contents, formation, shapes, and saturation of gel and capillary pores of cement paste , degrees of hydration, surface saturation of aggregates by applying into general and effective medium theories used in estimation of effective thermal conductivity of a multicomponent material. The developed model was calibrated and verified with experimental data of concrete cube samples for several mix proportions. A computer program was developed using APDL coding of ANSYS software to predict the thermal properties of concrete once mix proportion, chemical, physical and thermal properties of concrete materials are known. This model was coupled with the multicomponent heat of hydration model to improve the program’s ability to predict temperature rise with effects of variation of thermal properties with degree of hydration of cement. The developed multicomponent heat of hydration model was calibrated and verified with temperature rise data detained from several field tests which were carried out in several construction projects in Sri Lanka. Measured and predicted temperature response are in good agreement, and therefore the proposed model can be used to predict temperature rise when chemical composition, mix proportions, and thermal boundary conditions are known. Furthermore, the developed hydration model was used to obtain appropriate values for T1 (i.e. temperature drop between hydration peak and ambient temperature under local conditions which are required in design of water retaining structures.
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An Analysis of the influence of the field level hydraulic property approximations in storm water modelling
(2018) Wanniarachchi, SS; Wijesekera, NTS
This study analyses the effect of the catchment field approximations for accurate flood hydrograph prediction. Considering the availability of gauged data, the Karasnagala watershed of Attanagalu Oya, located in Gampaha district in the Western province of Sri Lanka was modelled with EPA SWMM 5. Following an event based approach, 3 days Minimum Inter event Time (MIT) and 0 mm/day Minimum inter Event Depth (MED) were used as the threshold. Fifty events were separated from the 1971 to 1982 period. Concave method and constant slope method were compared for baseflow separation in this study. Four major field approximation types were identified as stream geometrical parameters approximations, soil infiltration parameter approximations, approximation of watershed intermittent storages, and subcatchment delineation approximation. Quantitative representation of the catchment intermittent storages and qualitative representation of the connectivity of the catchment intermittent storages were identified as the objectives of the layout parameter optimization. Soil parameter approximations and the stream network geometry parameter approximations were verified by the field observations. Model calibration and verification revealed that EPA SWMM5 can be successfully used to develop regional Karasnagala watershed model with mean ratio of absolute error (MRAE) 0.289 for calibration, and 0.375 MRAE for verification. Incorporation of intermittent storages with optimized model layout obtained best fitting of hydrograph recession MRAE 0.167. Evaluation of available models and the modelling carried out with calibration & verification revealed that EPA SWMM 5 can be used to develop a rural watershed model. Field approximation for subcatchment lumping with a 16 sub basin configuration showed the marginal increment of modelling error when compared with distributed modelling. Stream parameter approximations revealed that the head water streams/lesser order streams parameters sensitivity is higher than the higher order streams. In soil parameter approximations, saturated hydraulic conductivity of the soil was the most influencing parameter.
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Validation of mechanistic empirical design approach for pavement design - case study for Sri Lanka
(2018) Jayarathna KARN; Mampearachchi WK
Pavement design is a vital part in new road construction and rehabilitation of roads. American Association of State Highway and Transportation Officials (AASHTO) pavement design guideline and Transport Research Laboratory (U.K) Road Note 31 (TRL RN-31) guideline are widely used for designing road pavements by most of the road agencies. Both these design guidelines are empirical guidelines and based on empirical formulas developed from experimental studies conducted in extreme weather conditions. In recognition of the potential of analysing pavements and predicting their performance, pavement design agencies have been encouraging the movement towards mechanistic empirical pavement design methods. Performance models used for the empirical pavement designs are basically derived from experiments which are conducted in controlled laboratory conditions. So it should be validated before utilising for the road pavement designs. The aim of the research was to check the applicability of Mechanistic Empirical (M-E) models developed by Austroad guide for tropical climatic conditions prevails in Sri Lankan roads. The computer program CIRCLY which is based on Austroad guide was used for the analysis. Cumulative Damage Factor (CDF) given by the computer program was compared with the in service pavement condition. Pavement Condition Index (PCI) was used to represent the pavement condition. PCI values were calculated only for structural based distresses as assessed by type, severity and density according to the ASTM method. CDF values obtained from CIRCLY were verified with the PCI values obtained from the pavement condition. Since PCI and CDF have a good relationship, CIRCLY software which is based on Austroad pavement design guideline could be introduced as a good analytical tool for designing road pavements in tropical climatic conditions. Then the research was focused on evaluating the suitability of a mechanistic empirical pavement design tool CIRCLY to investigate a pavement failure. In this study, failure of a non-structural surface road which is failed immediately after completing the construction was selected for the analysis. This road was designed according to the Overseas Road Note 31(ORN 31) and designed with a non-structural surface type, Double Bitumen Surface Treatment (DBST). Soil samples collected from critically damaged locations were tested. Results showed that the inadequate strength of the sub base layer as the reason to the failure. Failure investigations were done using a mechanistic tool CIRCLY and reliable reclamation method was proposed.