Browsing by Author "Wijekoon, S"

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item: Conference-Full-text
A comparative study to evaluate the effectiveness of different structural forms for medium-rise apartment buildings
(IEEE, 2022-07) Wijekoon, S; Jayasinghe, T; Herath, S; Herath, A; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
The rapid urban migration and the infrequency of spaces in megacities have become a challenge for all most all countries. To fulfill the housing requirements of the ever-growing population with the scarcity of valuable lands, the best solution is to come up with high-rise or medium-rise apartment buildings. Even though there are different structural forms that can be incorporated into high-rise apartment structures, most of the time structural designers select based on their experience and approach which are not effective all the time. The structural design for a given structure should be optimum in terms of structural performance and associated costs. Since wind and seismic forces govern the design of high-rise structures, those lateral forces are significant to be studied. So, this analytical study was carried out to evaluate the effectiveness of six different structural systems of 20-story RC (Reinforced Concrete) structures under the effect of wind and seismic loadings including a moment-resisting frame as the base model, four wall frame structures and a frame-tube structure. Models are compared based on the parameters such as maximum top storey displacement, inter-storey drift ratios, member forces and moments utilization, seismic induced base shear and human perception levels of lateral acceleration.
item: Thesis-Abstract
Conversion of dye sludge to RDF
(2014-08-08) Rubasingha, SN; De Alwis, A; Wijekoon, S
In Sri Lanka the Dye sludge production from textile industry is large. The large amount of produced dye sludge needs to be properly managed otherwise it will cause lot of environmental problems. Currently textile industries in Sri Lanka use the landfilling method to dispose dye sludge. Because of the landfilling method lot of environmental problems are surfaced, such as emission of toxic gases, ground water pollution and bad odour in environment. This study investigates the feasibility of using the waste dye sludge as fuel called Refused Derived Fuel (RDF). The method is used to produce RDF from dye sludge is mix dye sludge with other wastes available in textile industry. Other waste types which are supposed to use mix with dye sludge are fabrics, paper waste and saw dust. The mixing of waste dye sludge with other wastes in different compositions are investigated. Also different quality parameters of waste sludge and mixtures (after mixing with other wastes) are analysed.Calorifc values of waste sludge with different moisture content and mixtures with different waste fractions ,ash content,sulfer content,chlorine content,heavy metal content are main characterization parameters. Results analysed and it revealed that by mixing dye sludge with other wastes calorific value can be increased from 6 MJ/Kg to 22 MJ/Kg. By considering availability of the waste types during the last year most commonly used mixture composition is selected. We propose that waste dye sludge mixed with other waste types in textile industry is a suitable and effective alternative energy source in Sri Lanka
item: Conference-Extended-Abstract
Cross domain authentication with open ID for web-services
(2011) Siriwardena, P; Attenayake, S; Mahagederawatte, H; Wijekoon, S; Wijenayake, D; Dias, G
Cross domain authentication for web services is important when web services in one organization are accessed from another. This paper presents the implementations of cross domain authentication in web service environment with OpenID. OpenID integration for web-services enables authentication to web-services regardless of the domains requester and resource provider belong to. It enables wider use of web-services among users since OpenID has become quite popular. It also enhances the security aspect in web service authentication, since it eliminated the use passwords for authentication between requester and resource provider.
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Development of an Analytical and Numerical Model to Predict Elastic Wave Propagation Through Multi-metallic Systems
(IEEE, 2023-12-09) Wijekoon, S; Fernando, L; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
The behavior of multi-material layered systems that are subjected to high velocity impacts such as blast and impact is currently a topic of interest. This study investigates the impact-induced stress wave propagation through a multi-metallic layered medium subjected to low-velocity impact where only elastic waves are expected to be generated. In this study, four different test cases including a bi-metallic steel-titanium target and a steel-aluminium target, a tri-metallic steel-titanium-aluminium target, and a monolithic steel target were considered. The non-linear finite element code LS-DYNA was used to develop a two-dimensional axisymmetric numerical model and its output was compared with previously published experimental results obtained from a single-stage gas gun test that are in good agreement. An analytical model was developed using MATLAB that tracks and solves the interaction of each propagation wave in the flyer-target system. The associated Reimann problem for each interaction is identified and solved. The analytical model was validated by comparing its stress-time histories with the outputs obtained by the already validated numerical model and here too, the outcomes agreed well with one another. The main findings of this study highlight the reliability of the developed numerical and analytical model in predicting elastic wave propagation through a multi-metallic system.
item: Thesis-Abstract
Iron and manganese removal from textile effluents in anaerobic attached growth bioreactors
(11/30/2011) Gomes, PIA; Jayaweera, MW; Wijekoon, S
At present several primary and secondary treatment techniques have been used to remove iron (Fe) and manganese (Mn) from low polluting textile wastewaters. However past surveys and studies carried out in the industrial areas of Sri Lanka have revealed that contamination of waterways and groundwater with Fe and Mn has been still high indicating that proper methods are neither in existence nor efficient to remove them from low polluting wastewaters. Therefore in this article we discuss the performance of an upflow anaerobic bioreactor, which is used to remove Fe and Mn from textile wastewaters. A laboratory scale study on Fe and Mn removal in upflow anaerobic bioreactor of a working volume of 20 litres with coir fibre as the filter medium was investigated for a period of 312 days using a synthetic wastewater with similar physical and chemical characteristics of a typical textile effluent. The usage of coir fibre can be justified considering its high surface area per unit volume, hence providing more area for the biofilm formation. The maximum Fe and Mn levels considered were 10 mg/l and 5 mg/l respectively, which are the typical average values of textile effluents subsequent to the primary and secondary treatments in Sri Lanka. Ten sub experimental runs (R0-R9) were conducted with varying HRTs (5 days to 1 day), ratios of COD:SO42- (20 to 3.5), Fe levels (0.005 to 10 mg/l) and Mn levels (0 to 5 mg/l). During initial stages good gas production, high COD removal and relatively low sulphate reduction were observed, indicating major proliferation of methane producing bacteria (MPBs). COD:SO42- of 3.5 was identified as the optimum point at which sulphate reducing bacteria (SRBs) out competed MPBs and further reduction of this ratio caused total and/or significant inhibition of MPBs, thus making conditions favourable for bacterial immobilisation of Fe and Mn. After this point the gas production ceased while the system started giving rotten egg smell, as a result of H2S production taking place due to the metabolism of SRBs. The results indicated highly satisfactory percentage of Fe and Mn removal, in which the effluent contained Fe and Mn below the permissible levels ( 1.6 mg/l and 1.1 mg/l for Fe and Mn respectively) stipulated by US National Pollution Discharge Elimination System (NPDES) for inland surface waters at HRTs higher than 3 days. Results of the mass balance showed more Fe accumulation (65%) in sediments whereas 27% in the filter media. On the other hand out of the accumulated Mn, sediments contained only 26%, where as 65% were found to be attached to the filter media. Both metals in sediments mainly consist in the form of sulphides, indicating a sulphate reduction being the major mechanism of removal. Most of metal ions attached on the filter media too seem to be a direct consequence of sulphate reduction. The high removal efficiencies suggested that the bioreactors consisting coirfibres are a very good low-cost method of removal of Fe and Mn from the textile effluents. Keywords: Bioreactor; Fe; methane producing bacteria; Mn; sulphate reducing bacteria; Textile effluents
item: Conference-Full-text
Selection of proper mode for pavement rehabilitation – a challenge for engineers
(2013-11-12) Wijekoon, S; Abeyruwan, H; Wickramasinghe, V
The Government of Sri Lanka is investing heavily on infrastructure development which is the gateway to the economic development of the country. Accordingly, a significant number of national, provincial and rural road projects have been implemented. Designs for most of these road projects are done according to the international standards. There are a number of techniques available to rehabilitate or upgrade pavements and the intended benefits cannot be reaped unless a judicious technique is followed. This paper covers an example of an estimating design equivalent standard axles and a comparison of two common surfacing techniques, viz., thin bituminous surfacing and thin asphalt surfacing. Pavement structure is analysed using mechanistic method. The significance of mechanistic method over empirical approach is highlighted. The fallacy of the belief that the design life of pavement increases monotonically with the thickness of asphalt layer is revealed. The analysis leads to the selection of suitable pavement structure.