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Journal Cover Engineer : Journal of the Institution of Engineers, Sri Lanka
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  This is an Open Access Journal Open Access journal
   ISSN (Print) 1800-1122
   Published by Sri Lanka Journals Online Homepage  [48 journals]
  • A Study on Reinforced Concrete Columns Partially Confined with Carbon
           Fibre Reinforced Polymer (CFRP)

    • Abstract: Although the use of carbon fibre reinforced polymer (CFRP) materials is considered as a very effective retrofitting technique for reinforced concrete columns, still it is the identification of cost reduction strategies that draws most of the attention since the use of CFRP materials is considered as more expensive than any other retrofitting method. Providing partial confinement in place of full confinement which is the current practice may be a viable option that allows for considerable cost savings while maintaining the required structural capacity. Although CFRP technology has been in use for several decades, some countries still do not have adequate technical know-how to use this technique effectively. As there are several design guidelines available globally, it is quite unclear which design guideline will provide an economical design while maintaining the required factor of safety. This paper presents an experimental study conducted using 17 specimens to investigate the strength increments due to external CFRP confinement of reinforced and unreinforced concrete columns. Reinforced concrete columns were provided with both full and partial confinement to study their strength and ductility increments. The volumetric ratio of CFRP was kept constant for partially confined columns to study the effect of the jacket arrangement pattern. The experimental failure loads obtained were reviewed against the theoretical values calculated using ACI and fib guidelines, to investigate the overall safety factors available when using each design guideline. The experimental results showed considerable strength and ductility increments in all of the fully and partially confined specimens. Although the volumetric ratio of CFRP was kept same for all partially confined columns, it was observed that depending on the jacket location, the strength and ductility increments would vary. It was also observed that both design guidelines give for fully confined reinforced concrete columns, a factor of safety exceeding 1.5. Published on 2017-10-31 00:00:00
       
  • System Dynamics Based Model for the Nachchaduwa Reservoir in the Malwathu
           Oya Basin, Sri Lanka

    • Abstract: Though Sri Lanka is a water rich country where many water resources development projects have been implemented, the country still very often faces many issues due to water scarcity. By improving the management of existing water resources development projects such issues could be addressed. The irrigation area coming under the Nachchaduwa Reservoir Scheme in the Malwathu Oya Basin has encountered severe water scarcities in the recent past. This paper presents a system dynamics based simulation model that will help in making decisions for managing the Nachchaduwa Reservoir for fulfilling the water requirements of its irrigation area. The model was developed using system dynamics concepts and the software used was Vensim Professional. The advantage of system dynamics modelling is its ability to model many different sectors such as water quantity, population, agriculture and economy using one single model making it possible to look at all sectors using the same model . The model developed for the Nachchaduwa Reservoir System comprised of the above sectors and was used to investigate several optional operation patterns of the system. Four different operational patterns were considered based on crop types and cropping areas. Initially, the developed model was tested for its applicability and thereafter it was used to determine the most suitable cropping pattern. The results indicate that the patterns consisting of 100% paddy during the Maha Season and 50% paddy and 50% maize during the Yala Season as the most suitable cropping patterns for the two seasons. The model also showed that the temporary increase in the population by the pilgrims and tourists visiting the area during festive seasons affects the amount of water available for crops. Published on 2017-10-31 00:00:00
       
  • Impact of Cost Control Techniques on Cost Overruns in Construction
           Projects

    • Abstract: Construction industry plays an important role in the development of a country. The success of any project will depends on how that project can achieve its objectives in terms of cost, quality and duration. In order to achieve success in a project, it would be essential to plan that project well and have a proper monitoring mechanism in place. Cost overrun is a major problem encountered by many contractors as it makes the profit of a project less secure for the contractor in addition to causing many other problems to all the parties involved. Good cost control techniques would be essential to solve those problems. Thus, it is important to identify cost controlling techniques and their impact on cost overruns. This study was done using a questionnaire survey conducted among C1-C5 grade contractors. The data collected were analysed by converting them into quantitative values using percentage analysis and weighted score analysis. The results indicate the cost controlling practices that are in frequent use and their importance in minimizing the cost overruns in order to reduce over budget and overheads while securing anticipated profits. Finally, it is suggested that CIDA (ICTAD) should encourage contractors to use cost controlling techniques, by conducting training programs, awareness programs, etc. It is also suggested to make the use of some of ICTAD documents mandatory. Published on 2017-10-31 00:00:00
       
  • From the Editor Vol.50 (4)

    • Abstract: No abstarct available Published on 2017-10-31 00:00:00
       
  • Mix Design Aspects of High Performance Concrete Comprised of Silica Fume
           and Fly Ash

    • Abstract: With massive developments taking place in the construction industry, the demand for high performance concrete (HPC) is steadily increasing. It is possible to use industrial by-products such as silica fume (SF) and fly ash (FA) as supplementary cementitious materials (SCMs), to enhance the attributes of HPC. Although numerous investigations have been carried out to identify the optimum replacement levels of these SCMs, some inconsistences are noticed in the results. In this context, a study was conducted to look into the combined effect of SF and FA on the strength and workability of HPC. Four SF replacement levels: 5%, 10%, 12.5%, and 15%; and five FA replacement levels: 0%, 5%, 10%, 15% and 20% were proposed. A total of nineteen mix proportions were used including a control mix. Water-binder ratio was kept constant at 0.35. The mixes were tested for 7 and 28-day compressive strengths and for their workability. Results obtained revealed that the maximum 7-day compressive strength was in the mix with 10% of SF with no FA and the maximum 28-day compressive strength was in the mix with 12.5% of SF and 5% of FA. The workability increased with the addition of fly ash while the SF content kept below 10%. In terms of economy, the best strength to cost ratio was found in the control mix. The extension of the k-value concept for the water/binder ratio found in EN 206 for SF-FA combinations revealed that the existing parameters kSF = 2.0 and kFA = 0.4 show a good correlation with the experimental results. Published on 2017-10-31 00:00:00
       
  • Unconstrained Segue Navigation for an Immersive Virtual Reality Experience

    • Abstract: Virtual reality (VR) is a rapidly growing field that has got innovative applications. Two main forms of VR content can be identified in the current applications --computer generated 3D models and adaptations of real world scenarios using digital imagery and video. However, real world adaptations are quite restrictive when it comes to interaction. These restrictions are due either to large storage needs, or to high computational needs, required to generate dynamic intermediate views. Thus, solutions through which real world simulation could be achieved in immersive and interactive VR environments are not available. The research presented in this paper is intended to provide a high degree of interaction to users who engage in immersive VR experiences related to real world adaptations. The solution offered is a navigable grid map of spherical panoramas, which uses a three stage approach. Firstly, intermediate views among spheres are approximated using novel mechanisms. Secondly, an optimization strategy is introduced based on visual locality in which the areas with a higher probability of immediate interaction are given more prominence for quality during rendering. Thirdly, smooth segue transition is achieved through a machine learning backed gesture input system. The three approaches when combined together allow for an intuitive virtual experience while ensuring optimal resource utilization. Published on 2017-10-31 00:00:00
       
  • Impact of Electric Vehicle Loads on the System Load Profile of Sri Lanka

    • Abstract: Electric vehicles (EVs) are being promoted worldwide because of the potential they have to address atmospheric pollution issues and relieve countries from the burdens associated with the use of liquid petroleum based transport fuels. Ever increasing environmental concerns, improvements to battery technologies, entry of new manufacturers and new vehicle models, and introduction of favourable fiscal policies have all contributed to the increase in EV penetration rates worldwide including Sri Lanka. However, it is not clear how the power system in Sri Lanka would face the challenge of this new and unknown demand which would get added to the already exiting demand profile and which would be a result of the stochastic nature of the battery charging behaviour of EVs. In this research study, EV charging modes and charger types available in the market were considered and a model was established to ascertain the relationship between the charging demand and the other contributory factors such as EV battery sizes, charge remaining at the commencement of recharging, charging rates at different places of the chronological load profile, charging habits of customers and time-of-use pricing (TOU) policies. The probability distribution of variables such as the time of commencement of charging and battery charge duration was considered at a significantly acceptable level. By combining the probability distribution curves of the said variables, several EV charge demand curves were established using Monte Carlo method and the charging demand curves were subsequently superimposed on the system load profile. While the proposed methodology gives an insight into the impact of the EV load on the system load profile, it also shows how an effective control of EV charging could bring down the operational costs and investment cost of a power system. Published on 2017-10-31 00:00:00
       
  • Prediction of Temperature Development in Concrete using Semi-adiabatic
           Temperature Measurements

    • Abstract: Temperature development in concrete is caused by the heat of hydration which can be measured using calorimetric methods. In this study, a semi adiabatic calorimeter test was used first to measure the temperature development in six distinct C35A concrete mixes, and then using a heat loss compensation method, adiabatic temperature rise profiles were predicted. Cement and fly ash quantities in the mixes were varied to study the variations of the temperature development. The study then developed a two dimensional temperature prediction model applicable to rectangular concrete elements, based on heat transfer equations associated with the Fourier equation. A Finite-difference discretization was used in the modelling. The model took into account the heat generation due to cement hydration, heat transfer within the concrete element, and heat interactions between the concrete element and its environment under various boundary conditions. The prediction model has the potential for making two-dimensional temperature predictions in mass concrete at varying times and locations. Finally, the temperature prediction model was used as a case study to study the temperature development in a concrete wall. The results highlight the possible influences of concrete thickness on the internal temperature development of concrete and how the temperature could be controlled by using appropriate concrete mixes. Published on 2017-09-10 00:00:00
       
  • From the Editor Vol.50 (3)

    • Abstract: No abstract available Published on 2017-09-10 00:00:00
       
  • Metals used in old Bridges in Sri Lanka and the Effects of their Material
           Properties on Capacity Estimations

    • Abstract: Most of the metal bridges that were built over 100 years ago are still in use in Sri Lanka. To ensure the safety of these bridges as well as their users, condition assessment of these old structures becomes essential. The details of these bridges such as their mechanical and fatigue properties and the types of materials used in these bridges are very important for assessing their condition. Therefore, this study on metals used in old bridges was carried out using a literature survey and our own experiments. Recommendations were given thereafter for the selection of the mechanical and fatigue properties that are appropriate for assessing the old metal bridges in the country. The recommended values for the ultimate tensile strength of wrought iron and mild steel are in the ranges 284 – 390 N/mm2 and 370 – 450 N/mm2 respectively; values of yield strength of wrought iron and mild steel are in the ranges 191 – 241 N/mm2 and 220 – 280 N/mm2 respectively and, mean fatigue strength at 10 million cycles for both wrought iron and mild steel is 190 N/mm2. Finally, the importance of selecting appropriate mechanical properties for estimating the current carrying capacity of metal bridges is presented using examples. It is observed that the error in the estimation of the carrying capacity of a bridge resulting from the use of inappropriate mechanical properties could be as high as 33%. Published on 2017-09-10 00:00:00
       
 
 
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