Master of Science in Civil Engineering

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item: Thesis-Abstract
A Fuzzy approach to handle uncertainty and vagueness in life cycle costing for air conditioning systems
Perera, RCR; Perera, AADAJ
Air conditioning cost being the most cost effective element of building services in buildings because of its higher operating cost. In order to select a cost benefited one among the available types a life cycle cost analysis can be applied. Life cycle costing (LCC) by its definition is totally based on predictions. Accuracy in its application depends on how far the predictions covers the reality, handles the uncertainties involved and ultimately how far predicting. There are five major variables that contribute to the operating cost as well as to the inaccuracy of LCC. Those are: indoor temperature; outdoor temperature; relative humidity; number of occupants; and period of operating. These variables inherit very high uncertainty and vagueness. Thus, predictions and decision making has to provide space for handling them. The fuzzy set theory is employed to handle the inherent uncertainty and vagueness of the human decision making process. Hence, the hypothesis of the research was "Fuzzy expert system will address the problem". Conducting interviews and questionnaire surveys, with air conditioning design experts, the knowledge for the knowledgebase and decision-making logic for inference engine of the system were established. Then the system was prototyped in MATLAB Rll TM. Traditional methods can process only descriptive data while fuzzy system can process both descriptive and non-descriptive (continuous) data and produce accurate output. For example, indoor temperature and number of occupants are changing almost every minute. This dynamicity is effectively accommodated in fuzzy membership functions. Since fuzzy systems can do multi-variant manipulating for sensitivity analysis, the contribution of all the input variables towards the output variable "change in operating cost" can be obtained at the same time. Finally, the developed system was tested for its accuracy in prediction of operating cost with data from hotel buildings covering the data taken from questionnaire survey and then with a real set of data to govern the whole system behavior. It exhibited 80% of accuracy. The thesis describes the approach, development of model and the testing in detail. Key words: Life Cycle Costing (LCC), air conditioning, uncertainties, vagueness, Fuzzy logic
item: Thesis-Full-text
A Hybrid approach to the representation and processing of design standards
Neilson, AI
This thesis presents an environment for the modelling and processing of structural design standards. This environment is known as SADA, an acronym for Standards Automated Design Assistant. SADA addresses many of the drawbacks conventionally associated with design standards and existing models of design standards. A study of existing standards models and design standards was carried out, which resulted in the identification of a number of key issues, including:  structural design standards are ambiguous and are therefore subject to interpretation;  structural design standards generally address standard or routine design contexts, existing standards models fail to recognise this;  existing models are generally opaque in nature: i. it is not clear to the user how the standards have been modeled ii. processing of the standard is a 'black-box' activity, furthermore; iii. users have no control over the modelling or processing activities. SADA consists of four main modules, each consisting of several components:  Code Information Base;  Processing Module;  Dependency Network Generator;  Design Case Base. Each module performs its designated tasks contributing to the overall functionality of SADA. Nurnerous standards can be encapsulated and. browsed in a hypertext manner within the SADA model. SADA supports the production of designs within the scope of the standards contained in the model. Standard and non-standard contexts are distinguished. A procedural approach is adopted for the production of standard or routine designs. Case Based support is provided for handling non-standard designs. A conformance checking facility is provided for designs produced within SADA, and independently. An applicability checking feature easures standards are not applied out of context. Various features giving the user control over the modelling and processing of the standards contained in SADA have been implemented.
item: Thesis-Abstract
A methamatical model study to forcast inflow to Senanayake Samudra
Dias, PPG; Kariyawasam, C
The Objective of this Study is to develop a Mathematical Model to Forecast Inflows to Senanayake Samudra, given the rainfall in its catchment. This forecast can effectively be used in establishing the reservoir operating criteria. The Model is a self cleansing one which will modify its basic parameters as new data are fed in. The Water Balance Equation is used to develop the Model. Original plan was to collect the rainfall data for the past thirty years of all the rainfall stations within and adjoining the catchment and characteristics of the basin. However the useful rainfall data were available only for the past five years. Hence the Monthly Model and the Weekly Model were developed with the available data.
item: Thesis-Abstract
A New test for the evaluation of air classifier performance
McNabb, MB
sciency of mechanically extracting valuable resources from municipal solid waste (MSW). With today's techniques, resources such as combustibles, aluminum, glass, and ferrous materials can be extracted from ordinary refuse, processed, and returned to society for further use. This thesis examines one aspect of resource recovery engineering, namely the separation of MSW combustibles from noncombustibles by air classification. The combustible or organic fraction of MSW is valuable to society because it can be processed into refuse derived fuel (RDF) which power companies can mix with coal and burn in their combustion chanbers to create the steam that operates electric generators. Recovered combustibles are of greatest value when they are of high "purity" or rather are free from the contamination of noncombustibles, have a high energy value per unit mass, and require minimal processing. Problems caused by contaminants in RDF include glass slagging on the combustion chamber grates, increased residue left after burning, and a lowering of the RDF energy value.
item: Thesis-Abstract
A preliminary assessment of the Gal Oya water management project
Atukorala, NT; Kariyawasam, C
The Galoya Irrigation Project is the first multipurpose Scheme started in Sri Lanka. The project was commissioned in the year 1956. After nearly over 20 yrs. of its existence the project was in a rather poor condition. The original project served an area of 45,000 Acs, however after over 23 yrs, Irrigation facilities were available only for nearly 32,500 Acs for Maha & 19,250 Acs for Yala. The Gal Oya rehabilitation project was funded by the USAID and commenced in 1980 and continued beyond 1985. This study analyses the impact of the project on the work done from 1980 to 1985 (Most of the work was done during this period) The study was centered mainly on the aspects connected to irrigation as delving into other areas of assessment would be a vast exercise. The Irrigation aspect covered the following fields and the findings are. a. The Social Aspect With the rehabilitation programme there was a turn around of behavior of farmers. For example vandalism was reduced to almost nothing. No structures were damaged and no bunds cut. Third parties were not approached regarding water issues. Cultivation-calendar was adhered to as planned at the cultivation meetings. b. Water management and duty of water Rehabilitation of the project successfully improved a. The water conveyance capacity b. The water control capacity c. The water measurement capacity The foregoing enabled a very effective water management programme to be introduced and is being followed even today. This involved a computer programme with a very satisfactory feedback system. A number of water control structures were installed where necessary enabling the optimum use of water and preventing wastage. This measure improved the duty of water from pre-project value of 5.2 acft/Ac to the post project figure of 3.68 acft/Ac. c. Paddy production There was a gradual increase in the acreage and the Yield /Ac as the project progressed. The total acreage increased from pre-project 19,250 Acs Yala to post-project 53,000 Ac s Yala in 1985. Maha Acreages were pre-project 32,500 Acs to post-project 53,000 Acs. The increase in yield was pre project 34 bushels/Ac in 1979 to post project 60 bushels/Ac in 1985. The Yield is expected to increase further with the increase in confidence in the delivery schedules of water prompting greater agronomic imputs & increased labour inputs. Incidentally the yield in 1986 was 66.4 bushels/Ac. and in 1987 it was 70.5 bu. shels,/Ac. d. Economic Evaluation An economic evaluation was done taking into account only the increase in production of paddy and the .IRR was found to be 33.8%. However when the impact of the project as a whole is considered the fact that this project has raised the standard of living of the farmers within the project, created a sense of civic obligation among them together with a spin off of additional employment etc. cannot be underscored thus enabling this rehabilitation project as an example suitable for imitation in other rehabilitation projects to be taken up in the future.
item: Thesis-Abstract
A Study of customer satisfaction and application of QFD for quality improvement in residential apartments
Samarajeewa, KGA; Gunawardena, ND
There has been a significant growth in the residential apartment market in Sri Lanka during the last decade. The main reasons behind this upsurge include the growth of population, changes in living patterns and the soaring prices of property particularly in urban areas of the country. Sustainability of this segment of construction depends to a greater extent on the ability of developers to satisfy customer requirements in the long run. At present, most of the residential apartments are designed without the involvement of potential users or customers. When there is a communication gap among the parties, particularly with respect to user requirements, the goal of customer satisfaction and high quality services cannot be achieved. To ensure defects free and user-friendly form of residential apartments, the right blend of design, construction and operation phases is vital. This study has analyzed the information obtained through questionnaire survey to measure occupants' perception of characteristics of their apartment and its surroundings in terms of both 'importance' and 'quality'. The analysis considered both the private and public sector apartments and its process, critical issues regarding housing and customer attitudes were identified. Further, the results of the study revealed that understanding and determining the real customer requirements are essential for the sustainability of the residential apartment business; to address this issue, Quality Function Deployment (QFD) technique could be used quite successfully and if there is a mechanism to listen.to the voice of the customers such as the Post Occupancy Evaluation (POE) surveys presented in this research or any other that enables the involvement of users during the early stages. Key words: Residential apartments, Quality, _.Customer satisfaction, Post Occupancy Evaluation, Quality Function Deployment
item: Thesis-Abstract
A study of the present and potential in Sri Lanka
Pattiaratchi, DS; Madusuthanan, N
The Government had initiated a National Agricultural, Food and Nutrition Strategy to-assess Sri Lanka's agricultural and food situation and establish priorities for sectoral development. Since the plan involves the use of land, a computerized Land Information System was set up to facilitate the analysis and evaluation of Land use in Sri Lanka. A Radio Shack Model II micro-computer was used for this purpose. Data on Soils, climate, topography and present land use were fed into the computerized data bank. The grid cell system of data storage was used. The dimensions or a grid cell are 1.05 x 2.1 Km covering an extent of 224 hectares. The final maps are plotted to a scale of 1:500,000. The soi1 data were obtained from the manuscript copies or reconnaissance soli maps drawn to a scale of 1:63,630 available at the Land Use Division. The climatic data were obtained from the agro-climatic data and rainfall probability maps produced by the Land and Water Use Division in 1976 and 1983 respectively. Slope data were compiled with the help of contour Lines on Topographic maps of scale 1:63,360. Data on present land use were obtained from three sources viz. (a) Survey Department (1981) 1:100,000 and 1:50,000 scale maps of Polonnaruwa, Batticaloa, Kandy and Colombo(final maps) and Puttalam, Gampaha, Kegalle, Kurunegala, Badulla, Ampara and Matale Districts (prelimlnary maps) (b) Land Use Division (1980 to 1983) 1: 63,360 and 1:50,000 scale maps of Matara, Nuwara Eliya, part of Ratnapura and Hambantota Districts(c) Huntings Survey Corporatlon (1956) 1: 6 3,360 scale maps for the balance Districts updated by date from Topographic sheets of 1970s and data on Irrigation schemes implemented by the Irrigation Department and Mahaweli Authority. Data on soils, climate and topography were assessed to determine suitabilility of lands for (a) rainfed annual crops (b) irrigation upland annual crops (c) rainted paddy under puddle conditions (d) irrigated paddy under puddled conditions (e) rainfed sugar cane (f) irrigated sugar cane (g) rainted minor perennial crops. Four classes of suitability as recommended in the FAO Framework for Land Evaluation Viz S1Highly Suitable, S2 Moderately Suitable, S3-Marginally Suitable and N Unsuitable were recognized in this exercise. Tables of district wise of land suitability classes were also complied. Secondly the present land use was analyzed with respect to the suitability classes. The map complied for this purpose shows locations at which the analyzed land use is practised giving the symbol of the suitability class. A table giving the district wise extents is also complied. Thirdly the potential locations for expansion of the considered land use is compiled. Only locations of class S1 and S2 suitability are considered. Lands under forest reserves, wild life parks, land earmarked for Mahaweli and other development projects and other reserves are shown with separate symbols F, P, M, D and R respectively for class Sl lands and f, p, m, d and r for class S2 lands. A districtwise extents table too is compiled.
item: Thesis-Abstract
A Systems approach to assess the vulnerability of buildings to bomb blast
Chandratilake, SRMSR; Dias, WPS
A blast event lies within the social system and involves people. Hence vulnerability to blast loading can be considered a socio-technical or "soft" system, where our ability to model and hence predict bounds on behaviour is poor. Even where the "hard" part of the system is concerned (i.e. structural response), blast loading is difficult to idealize and its effects cannot be fully predicted. For all the above reasons, the analysis of vulnerability to blast loading must be grounded in past experience. Grounded Theory is a way in which theory is built from phenomena. Theory is considered as being grounded in phenomena; the reliability of data forms the basis for claiming the phenomena exist. Once the specific phenomena in the different case studies have been identified, they can be generalized into concepts. Coherence among concepts is the appropriate grounds for theory formation and acceptance. Grounded Theory is "explicity emergent" and does not test a hypothesis. For the above reasons, Grounded Theory was used to structure this ill-structured research problem that also required a reliance on experience. The main objective of the study was to construct a hierarchy of concepts, which would constitute aspects that contribute to building vulnerability, using case histories. "Vulnerability" is treated as the top level concept, itself consisting of other concepts. Ten case studies of blast loading .were chosen. These represented a variety of building uses, structural form and construction material, and also reflected a variety of explosive types and different locations worldwide. Data (e.g. statements) from case histories were used to identify phenomena. It was possible to extract 63 phenomena relating to building vulnerability from these case studies; some concepts were repeated in the case study phenomena. It was observed that the concepts lent themselves to hierarchical structuring. Some of the concepts could be grouped into a single concept that "emerged" from the former. The 63 original phenomena were used to generate 52 concepts, at various levels in the hierarchy. The hierarchy that was constructed consisted of seven levels. Each emergent concept can be called a "holon" - i.e. it is a whole when considering its constituent lower level concepts, and a part when considering an emergent higher level concept it contributes towards. The top levels of the hierarchy obtained differed somewhat from those that were previously constructed using "top down" approaches based largely on literature surveys; this demonstrates the value of a "bottom up" approach that seeks to "listen to the data" from case studies. Level 2 of the hierarchy shows that the vulnerability due to blast effects is a social process where context too plays a key role; hence due consideration must be given to context when seeking to assess or reduce vulnerability. Some of the concepts that were frequently repeated in the case study phenomena are "advance warning", "standoff distance", "nature of terrorism", "confinement", "building layout", "structural redundancy", "security" and "glass"; a method of weighting is required to account for the importance of such concepts (reflected in their repetition) within the hierarchy. The assessment procedure combines existing numerical models as well as ways of processing vague information and expert judgments. It is also a very flexible tool which allows the handling of various types of artifacts which are significantly different from past experience. Experts will use linguistic assessments to measure the evidence about the dependability of holons to sustain their function in a particular blast incident. Linguistic assessments are matched to interval probability numbers. An interval number is used to capture, in practical manner, features of fuzziness and incompleteness. Interval Probability Theory (IPT) is used to combine evidential support values throughout the hierarchy. A computer implementation of the model was developed to show its potential for practical use. The software developed was used to apply the methodology to a building located in the heart of Colombo. The interpretation of results shows the potential of the model to be used as a management tool for practical decision making.
item: Thesis-Abstract
An analysis of a univariate and bivariate time series
De Silva, HN
The first part of this report is an univariate Analysis of time series data of the Southern Oscillation Index. The analysis was done in both the time domain and the frequency domain. The nature of the phenomena is such that it seems to suggest that prediction of the future will very definitely be linked to the past. Examination of the autocorrelation function and the partial auto correlation function proved that this was very definitely true. Analysis in the time domain gave some useful results and it was possible to come up with an AR(4) model. Frequency domain analysis was not as useful since it was not possible to find constant amplitudes and phase values at the dominant frequencies. However Spectral Analysis was useful in determining the periodicity of the data, and this was found to be very close to the periodicity of the El-Nino phenomena to which the Southern Oscillation is reputed to be very closely linked. The analysis was done mainly using Splus, a very convenient statistical package. The second part of this report 1S a bivariate analysis of time series data, comprising of the above mentioned SOl series, and a series of Sea Surface Temperature (SST) data. Again the analysis was done in both the time and frequency domains. In the time domain it was attempted to fit an ARMAX model. It was possible to come up with a model comprising of three SOl terms and four moving average (MA) terms. The model provided reasonable fit, but it was not completely satisfactory. Frequency domain analysis provided some interesting results even though a definite predictor model was not obtained. Analysis of the phase, gain and coherency plots' together with an analysis of the auto spectra lead to a conclusion that a definite correlation between the two series existed. The significant frequencies at which such correlation was found corresponded to the recurrence interval range of the EL-Nino phenomena.
item: Thesis-Full-text
Analysis and development of high rate composting system using municipal solid waste in Sri Lanka
Manipura, WMJASB; De Alwis, A; Pilapitiya, S; Pathinathar, S
Municipal solid waste has become a major problem in every country in terms of public health and environmental damage. As a developing country, Sri Lanka too faces the same challenge not only by public health and environmental damage, but also in finding an affordable yet effective technology, which is socially and economically acceptable. Municipal Solid Waste (MSW) is qualitatively heterogeneous. Therefore, it is difficult to find a unique solution for proper treatment. I.e. The solution is always an integrated one, which consists of sorting, biological/thermal/chemical treatment, recycling and land filling. However quantification and characterization of solid waste in a given area are important factors prior to selecting suitable technology. Therefore, it is required to find waste quantity, composition, density, moisture content, annual rate of waste generation and calorific value of waste etc in a given area. In Sri Lanka, moisture content and organic fraction are reasonably high and lack of high thermal value materials in solid waste stream, have lead to an overall low calorific value of MSW. The general practice for handling the MSW is low rate compo sting systems. Most have been failed due to poor process management, lack of knowledge of proper operation (feedstock formulation, process control, end point indicators), poor product quality, long lead-time, weaker community participation and lack of public awareness. In all systems existing at present bad odor and leachate are unsolved issues. These systems have largely been controlled by default rather than by design. Thus, losing the public confidence on composting is inevitable. Properly engineered composting systems require to monitor and control of key parameters such as aeration, C/N ratio of feedstock, pile temperature, moisture content and particle size. The broad objectives of the research were, a detailed review of solid waste management practices in Sri Lanka and process of compo sting, Identification of composting strategies & evaluation of systems, and design of a high rate in-vessel composting system. During the design, it was considered to maintain the optimum environmental conditions for higher rate of decomposition by microbial activities, aeration demands, and required moisture content throughout the process. The main component of the model is a rotating drum reactor, which is operated under the thermophilic temperature conditions. The rate of decomposition at thermophilic temperatures is much higher (low residence time) than the mesophilic temperatures. A shredder could be used for size reduction of incoming feed in order to determine the optimum particle size. As source separation is very poor in Sri Lanka, this research addresses the possibility of using a semi-mechanized waste segregation device at the secondary stage. Special care was taken to control the odor and leachate of the system. On the other hand, the confidence on .low rate windrow / static pile compo sting among the people have been lost due to the process mismanagement. Therefore, the design offers to have an energy optimized semi mechanized system in which minimum labor contact with the waste occurs. The reactor is operated by a feedback control system, in which real-time monitoring of critical parameters are done. Based on the existing value and the set point (optimum value for each parameter: moisture and aeration), the control action is taken. Further, intermittent rotation of the reactor facilitates the proper temperature distribution inside, particle size reduction and uniform porosity throughout the mixture while reducing the energy consumption faced by the continuous operated system. Sensor setup at different heights of the reactor monitors the temperature and moisture content along the axis of the system. It has been observed that moisture is the limiting factor, when the temperature feedback control system is used in the composting. However, real-time monitoring of the moisture content avoids this difficulty. Further, weak pathogen inactivation is a major drawback found in most of the manually turned systems. Intermittent rotation and temperature feedback control system ensure the proper temperature distribution across the reactor and mixes the matrix properly in order to subject to uniform temperature throughout the mass. The modular basis helps for easy movement and it consumes less space compared to the windrow system. According to the national database on solid waste in Sri Lanka, 88% of Local Authorities collects less than 10 Tons per day. This shows the possibility of use of modular units in areas, where space is limited. Close monitoring of the critical parameters of the system helps to maintain optimal decomposition rates while ensuring consisted product quality during the decomposition. Since organic farming is a growing area in export-oriented agriculture (Tea, vegetables) in our country, this research helps to produce a good soil conditioner (with consistent finished product) using MSW while solving a major environmental problem. Tea plantation companies put special attention to identify the requirements of quality standards for the production of famous 'Ceylon Tea'. Hence as a part of this work, analysis of the critical parameters of the compost, manufactured by different organizations in the country that use solid waste as the substrate was carried out. It is important to match compo sting quality and the particular plantation requirement to develop a sustainable market for the compost produced using MSW. This has been particularly lacking in the Sri Lankan market with the compost producer hoping to realize a good price for anything that is produced; an expectation that had not been realized.
item: Thesis-Full-text
Analysis and initial design of civil engineering structures using structural optimization
(2023) Lowhikan SS; Mallikarachchi HMYC; Herath HMST
Structural optimization of solids aims to find the optimal designs of structures by minimizing a constrained objective function such as the material compliance within a given problem domain. This constrained optimization problem is subjected to a set of displacement and load boundary conditions which in turn will be minimized with respect to a structural parameter. Although various structural optimization techniques have a sound mathematical basis, the practical constructability of optimal designs poses a great challenge in the manufacturing stage. The recent development in additive manufacturing partially side-steps this problem predominantly in the domain of Mechanical Engineering. However, in Civil Engineering structures, there is a great possibility of utilizing these optimization tools, especially in precast constructions. Currently, there is only a limited number of unified frameworks which output ready to manufacture parametric Computer-Aided Design (CAD) of the optimal designs. From a generative design perspective, it is essential to have a single platform that outputs a structurally optimized CAD model because CAD models are an integral part of most industrial product development and manufacturing stages. This study focuses on developing a novel unified workflow handling topology, layout and size optimization in a single parametric platform (Rhino-Grasshopper) which outputs a ready-to-manufacture CAD model with the assessment of their structural integrity. In the proposed method, the first topology optimized pixel model is generated for any two-dimensional problem and converted into a one-pixel-wide chain model using skeletonization. From the obtained skeleton, a spatial frame structure is extracted, and then its member sizes and layout are optimized. Finally, the CAD model is generated using Constructive Solid Geometry (CSG) trees and its structural performance is assessed. In addition, industry-standard structural sections can be assigned to the CAD model to be analyzed and designed in accordance with standard codes of practice.
item: Thesis-Abstract
Analysis of operation and maintenance of giant's tank scheme
Thuraisingham, M; Kariyawasam, C
Giant's tank is located in Mannar district of the Northern Province in Sri Lanka. This tank has 10 sluices, 3 taking off from the inlet channel and the balance 7 from the tank. This scheme consists 162 minor tanks which are balancing reservoirs for the irrigable area of 24,438 acres. During dry periods, tailend farmers faced lot of water problems due to cascade type tanks distribution systems and improper maintenance of the scheme, mainly due to the shortage of funds. Few year s ago the Government of Sri Lanka decided to recover some of the Operation and Maintenance Cost from the farmers. It was estimated that the cost of operating and maintaining a major irrigation scheme is about, Rs. 200 per acre. The government of Sri Lanka requested the farmers to pay Rs. 100 per acre and the government agreed to provide the balance. The government plan" was to increase the farmer’s contribution by Rs. 20 each year for five years. According to this plan after the fifth year total cost of operating and maintaining the systems will be met out of the farmer’s contribution. However the O & M fee collection was not successful. The farmer’s contribution dropped annually. As such the government decided to keep the farmer s contribution the initial Rs. 100 level. One of the reasons for not paying the O & M fee is that the farmer's feel that the irrigation water is not equally distributed. This report suggests an alternate way to distribute the cost of operation and, maintenance.
item: Thesis-Abstract
Analysis of safety on Moratuwa - Egoda Uyana road and identification of reasons and possible mitigatory measures
(2014-07-10) Fernando, WAJE; Kumarage, AS
Road accidents have been on the upward trend the world over including Sri Lanka. According to Traffic Police Statistics, about one hundred road accidents are reported daily in the island, of which, about five to six are fatal. This state of affairs, particularly relating to Sri Lanka could be attributed to several factors, some of which would seem to be peculiar to this country. Among them are the heavy influx of motor vehicles. (particularly after liberalisation of imports), the population explosion, increased employment From Table 1.1 it is seen that the cumulative vehicle population has increased from 156, 334 in 1974 to 1,244,653 in 1995 on an average of 10.4o/o per annum. The ESCAP region covering Asia and the Pacific is one of the fastest developing regions in the world. Since the mid 1980's the rate of increase of GDP in developing ESCAP countries has been about double the global rates. In the 1985-1991 period, the share of the world trade of ESCAP countries increased from 40.0% in 1985 to 47.2% in 1991 (Turner, 1993) resulting in increasing traffic on roads.
item: Thesis-Abstract
Analysis on the culture of professionals in the Sri Lankan construction industry
Kasthurirathna, KTACG; Sugathadasa, R
Construction industry is very significant to the Sri Lankan national economy. Therefore success in the construction industry always makes the way to success of a country. The construction industry is reliant upon human exchanges and large number of stakeholders in construction projects makes the industry prone to disputes. Because of the diversified nature of the industry, different values are held by different groups of individuals. When successfully managed, however, differences in the culture can lead to innovative business practices and faster and better learning within the organization. Keeping all aforementioned facts in mind, the research seeks to investigate what is the culture of the professionals in Sri Lankan construction industry. Many cultural concepts such as Deal and Kennedy's model, Charles Handy's model, Garath Morgan's findings and many more were studied and evaluated beforehand the selection of Hofstede's four-dimensional cultural model as the foundation concept for the research. By using the suitably adapted version of the Hofstede's Values Survey Module82 questionnaire (VSM82) and methodology, a survey was carried out among 300 construction professionals comprising Architects, Engineers and Quantity Surveyors, working within Sri Lanka to determine the cultural values of the construction industry. From this sample 180 professionals were chosen to represent the overall construction industry. Remaining 120 was divided in to two categories according to their industry of work engagement as road and building construction industry professionals. The results obtained from the 300 questionnaires were analyzed using Hofstede's four-factor approach of Power distance; Uncertainty avoidance, Individualism and Masculinity. The research revealed differences as well as similarities of the cultural characteristics of Sri Lankan construction professionals as a whole and the professionals in the building and road construction industry. The reasons for the changes as well as similarities , revealed a fascinating insight in to the professional's culture of the Sri Lankan construction industry.
item: Thesis-Full-text
Application of CFRP composite for sustainable solution of corroded slab system due to low nominal cover case study on nerd slab system
(2023) Ganewattha CK; Gamage JCPH
Carbon Fiber Reinforced Polymer (CFRP) strengthening technique had been shown excellent performance in externally strengthening reinforced concrete (RC) elements due to their superior properties compared to the alternative strengthening techniques. A substantial number of studies have been done to study the behavior of externally bonded CFRP strengthened RC elements. However, as per the knowledge, while most studies have focused on the external strengthening of RC beams using CFRP, and very few studies have focused on strengthening the pre-stressed beams and slabs. Pre-stressed concrete is most popular building technique in construction buildings. Steel corrosion is recognized as the most serious and dominant mechanisms of deterioration for concrete structures. Subsequently, the capacity of the pre-tension elements decreases after exposure to corrosion. NERD center slab system faces such unacceptable losses in load carrying capacity, stiffness, and ductility due to severe corrosion in pre-stressed beams. This study focuses on how CFRP can go for a load increment after reaching its ultimate load carrying capacity. The test procedure was arranged in two stages. The first stage testing was used to show the performance/ behavior of composite slab specimen and pre-stressed beam, with the application of load. The second stage of testing was carried out to make comparison between the structural performance of retrofitted and strengthen specimens. Specimens were selected for retrofitting after application of loading in stage 1. The total of 12 specimens were exposed to the loading and behavior of each of the specimen were observed. Specimens were selected as slabs and eight number of them were composite slabs with or without shear links which have overall dimensions equal to 1800 * 600 mm and other four were pre-stressed beams with overall dimensions of 1800 mm in length. In this study, CFRP is proposed as the economical solution which does not touch the structural integrity of the structure. All the specimens were tested using universal loading machine. In stage 1, specimens were loaded up to its ultimate failure. In stage 2, all the tested specimens were retrofitted using CFRP. In total number of six specimens were used for retrofitting. Another six specimens were also strengthened using CFRP before loading. In each stage of loading several observations were done. Such as mode of failure, cracking width distribution, ultimate load, and each composite panel's corresponding deflection were also recorded. In stage 1, flexural and shear cracks propagated in the pre-stressed beam and the beam failed at the applied load of more than 50 kN. Stage 2 focused on the performance/ behavior of the retrofitted and strengthened specimen after application of CFRP. The results from stage 2 showed a considerable reduction (nearly 20%) in loading of retrofitted/ strengthened composite slabs compared to control specimens. Difference in failure pattern is caused for this discrepancy in load demand of second stage. The experimental results showed some satisfactory performance in regaining the lost strength of the composite specimens due to corrosion.
item: Thesis-Abstract
Application of mathematical modelling for assessment of nearshore wave climate
Ranasinghe, DPL; Gunaratna, PP
In Sri Lanka, nearshore wave climate is influenced by the simultaneous occurrence of swell waves approaching from a more or less southerly direction and sea waves mainly influenced by monsoonal weather pattern. Some nearshore areas are also vulnerable for occasional impact of cyclonic wave conditions. This complexity and high degree of temporal and spatial variability of waves clearly emphasize the need for accurate assessment of near shore wave climate. The lack of wave recordings at nearshore location restricts the assessment of nearshore wave climate to some extent. This deficiency in wave data can be overcome by transforming waves from location at which wave data are available through wave propagation modelling. This research study is aimed to develop two dimensional mathematical model based on an irregular wave description capable of simulating wave propagation from offshore to nearshore considering wave transformations due to shoaling, refraction , wave breaking and bottom friction dissipation. The wave conservation equation and the model of Battjes and Janssen were used as the basis to develop the model. Galle (70m depth) is considered as offshore location which represents the entire deep water wave climate off the southern offshore coast. Hambantota (17m depth) and Kudawella(I5m depth) were selected as nearshore locations to establish the directional wavestatistics for swell and sea waves by applying the developed mathematical model. Finally based on obtained nearshore wave data base, predictions for extreme wave conditions were made as design wave parameters for coastal and harbour structures. Extremewave heights analysis were done for both offshore and nearshore locations in southerncoast of Sri Lanka using two statistical extreme value probability distributions, namely Gumbel (Fischer-Tippet Type 1) distribution and the Weibull distribution
item: Thesis-Abstract
Application of mathematical modelling for predicting coastline evolution
Fernando, MSL; Samarawickrama, SP
Increased river sand mining in the west of Sri Lanka has led to coastal erosion over the last few decades. Erosion has been particularly severe along the coast north of the Maha Oya. The CRMP project, which included structures and sand nourishment, was the most recent scheme to stabilize this coast. However, the shoreline to the north of the last structure began eroding just two years after the completion of this project. The objective of this study was to set up and calibrate a mathematical model of shoreline change to understand this erosion and to evaluate options for future protection. The one-line model GENESIS was selected and an extensive sensitivity analysis carried out to assess the reliability of the results. Available data - which includes shoreline surveys before, during and after the CRMP project and long term wave data recorded at Colombo - was augmented by measurements of the shoreline north of the last structure. Shore profiles and grain sizes were also obtained. The model was applied to the shoreline changes observed between and northwards of the last seven groynes of the CRMP project both during and after construction. The model results were in reasonable agreement with observations. The high erosion rates north of the last structure were due to the reduced sand supply from the south, i.e. the structures to the south were trapping more of the nourished sand than expected in the design of the CRMP project. The model was used to assess options - including the groynes constructed recently - for the protection of this shoreline. While different options were able to stabilize specific areas, erosion will continue somewhere until the sand supply is augmented by further sand nourishment. The study demonstrated the utility of detailed, shoreline monitoring for the quantification of changes and the calibration of models.
item: Thesis-Abstract
Application of the electrical analog technique to study a limestone aquifer
Karunasena, R; Senarath, DCH
This dissertation describes a hydrological study of the Vanathavillu Limestone aquifer using the Electrical Resister Analogue Techniques. Vanathavillu is situated about 18 km, north of Puttalam covering an area of about 80 km2. It is considered to be an isolated basin with the boundaries in the north at Kalaoya delta and the other boundaries being impermeable due to faults on the west and the south and an outcrop of basement in the east. The basin consists of two main water bearing strata namely, the upper Moongil Aru formation of quaternary age and a lower Limestone aquifer of Miocene age. Some observations had been carried out during the past two decade with reference to the geology and the hydrogeology of the area. The aquifer parameters and hydrological factors such as recharge and abstraction have been estimated with some degree of uncertainty. The application of the Electrical Analog Technique in the present study is to obtain refined estimates of these parameters and thereby predict the maximum usefulness of the aquifer. In using the Analog method, more weightage was given to some data such as piezometric head contours already established so that the uncertain data could be checked for their validity. Based on the numerical values of the aquifer parameters that were established and the recharge quantities that were evaluated, an overall evaluation of the aquifer as a source of water supply is carried out.
item: Thesis-Abstract
Application of unsaturated shear strength properties in slope stability analysis
Rathnasiri, RM; peiris,TA; Puswewala, UGA
Unsaturated soil mechanics is becoming increasingly popular in the world of Geotechnical Engineering due to the additional shear strength that unsaturated soils possess compared to saturated soils and specific problems that are associated with unsaturated soils. In this thesis, unsaturated shear strength properties of a selected residual soil are derived and their effects on the stability of slopes are investigated. The shear strength function and the Soil Water Characteristic Curve (SWCC) of the soil found at Pussallawa landslide are developed through a laboratory testing programme. Thereafter, the Pussallawa landslide is analysed under saturated and unsaturated conditions depending on the location of the water table, using shear strength parameters obtained from the laboratory testing programme. In addition, the Kahagalla landslide and a hypothetical cut slope are analysed similarly assuming different locations of water table. An EXCEL spreadsheet is developed to analyse stability of slopes using saturated and unsaturated shear strength of soils. Results obtained for the hypothetical cut slope by the spreadsheet application developed here are compared with those given by the ,SLOPEIW software, using different methods available to analyse stability of slopes. This yields a comparison among the different methods of slope stability analysis. Results are presented in graphical and tabular form. As it is difficult to measure insitu suction values in local slopes at present, the parametric study done here gives an insight into the problem of landslides. This method can be refined to find a reliable factor of safety for slopes once methods are developed locally for insitu measurement of suction. The analysis shows that there is a significant improvement in the factor of safety when the slopes are unsaturated, compared to that when they are saturated and the factor of safety under unsaturated conditions increases as the depth to water table from the failure surface increases. It also shows how slopes can fail upon saturation.
item: Thesis-Abstract
Assessing Tsunami hazard and mitigation measures
Karunathilaka, AVAU; Hettiarachchi, SL; Samarawickrama, SP
The Indian Ocean Tsunami in 2004 caused widespread damage in the coastal regions of Sri Lanka. The extent of inundation and the associated damage varied significantly with the local near shore wave height, topography and the resistance offered to the overland flow. This study is concerned on a methodology to calculate and record the wave heights around Sri Lanka by a tsunami generated in Indu- Andaman region or Sunda trench and the mitigation measures which could be implement within the coastal region. As Sri Lanka is exposed to tsunamis, as indicated by the Indian Ocean Tsunami in 2004 and subsequent alerts in 2005 and 2007, it will be important to assess the risk of tsunamis for Sri Lanka in terms of tsunami arrival time, nearshore wave height, extent of inundation, period of risk etc. Online Software named ComMIT developed by the Indian Ocean Tsunami Warning System was used to calculate the tsunami wave heights along the coastal belt of Sri Lanka and it was selected after consideration of input parameters and the given output of some available tsunami software. Taking into consideration of the tsunami generation, deep water propagation and shallow water transformation, it is expected by this study to simulate various scenarios to arrive at an outcome which can be finally used to develop a database containing information to be effectively utilized by a tsunami early warning system. As part of the research, large scale physical modelling was developed to simulate tsunamis and testing was done by generating waves in the 2D flume of the Lanka Hydraulic Institute. Physical tests were carried out to assess the effectiveness of breakwaters and coastal vegetation as a tsunami impact mitigation measure and results on the effect of wave steepness and the porosity of the vegetation in reducing the tsunami wave heights were presented.