Engineer : Journal of the Institution of Engineers, Sri Lanka
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Open Access journal
ISSN (Print) 1800-1122
Published by Sri Lanka Journals Online [46 journals]
- Strategic Decision Support for Resolving Conflict Existing in Per Aru
basin located in Vavuniya district
Abstract: The graph model for conflict resolution (GMCR), along with its associated decision support system GMCR II, is employed for systematically studying the strategic aspects of a conflict existing in Per Aru basin. National Water Supply & Drainage Board has planned to build a reservoir on the Per Aru for the sole purpose of supplying drinking water to the urban areas of Vavuniya district. People who will be affected due to the inundation of their lands have shown resistance to the construction of the reservoir. Moreover, government organizations such as Forest Department and Wildlife Department also have expressed their concerns over the construction of a reservoir since that will have diverse impacts on forest lands and wildlife in the area that will be inundated by the proposed reservoir. The above three stakeholders, viz., National Water Supply & Drainage Board, affected people and government organizations suggest a few options to solve the conflict.The options are specific actions that can actually occur in a conflict. The decision support system, GMCR II, was used to investigate and resolve this conflict. The paper presents all the steps involved in the modeling of the conflict using GMCR II and analysis of the results obtained from the model. The National Water Supply & Drainage Board accepting to reduce the inundation area and agreeing to release sufficient environmental flow was resulted as the best possible solution acceptable for all the three parties.The solution includes affected people and Government Organizations agreeing for the construction of the reservoir at the original location.
ENGINEER, Vol. 47, No. 03, pp. 61-70, 2014 Published on 2016-02-01 00:00:00
- Design and Development of Rasp Bar Mill for Size Reduction of Maize
Abstract: Particle size affects many characteristics in the manufacturing process. Controlling the particle size helps to assure that the milled material will be consistent and repeatable with respect to firstly color, that is, uniform particles assure batch-to-batch color consistency, Secondly, flowability that is critical to packaging, tableting, weighing. Thirdly, uniformity, that is , consistent bulk density. Fourthly, density - helps control shipping costs and minimize dust. Fifthly, reconstitution, that assures the desired dissolution rate, Sixthly, chemical reaction that is vital for uniform, controlled chemical change. Finally, taste that allows precise portion control for consistent taste. The aim of this project is to design and develop a rasp bar mill for size reduction of maize seeds for different purposes. The fabricated rasp bar mill is capable of feeding maize around 60-180 kg/h, delivering of grits 60-90%, with sieve effectiveness 90-100% at a power requirement of 800-1400W,for different sieve perforation sizes of 5, 6, 7, 8 mm respectively. ENGINEER, Vol. 47, No. 03, pp. 39-47, 2014 Published on 2016-02-01 00:00:00
- Predicting Thermal Performance of Different Roof Systems by Using Decision
Abstract: This paper describes the use of decision tree method to predict thermal performance of several roof systems under different climate conditions. The decision tree method is a data mining technique which has competitive advantages over other methods such as simple and clear procedure, easy to understand without having rigorous mathematical and computational knowledge, etc. Results of 80energy simulation cases were used to demonstrate the applicability of this method in building energy simulation. These 80 simulation cases are based on five locations in five different climate zones, eight different roof systems, and two extreme climate conditions; warmest and coldest in a year of a particular location. The modelled decision tree has prediction accuracy of 84% on training data and 100% on test data. Addition to that, decision tree automatically ranked the best selection of roof system under prevailing climate conditions. The predicted values shown in each classified data subsets can be used as a reference with an accuracy of 6%to predict the indoor room temperature with the use of a particular roof system. Finally, derived decision rules and simplified guidelines from constructed decision tree are also provided in a tabular format for non-engineer users. ENGINEER, Vol. 47, No. 03, pp. 27-37, 2014 Published on 2016-02-01 00:00:00
- Criteria to Assess Rock Quarry Slope Stability and Design in Landslide
Vulnerable Areas of Sri Lanka: A Case Study at Thalathu Oya Rock Quarry
Abstract: The ultimate causative factor for the failure is rapid removal of toe support of the slope due to unplanned mining accompanied with uncontrolled blasting. There is also a natural causative factor behind, a naturally formed highly weathered slip surface, where along the slope failure has taken place. Secondary discontinuity created along the well-developed foliation plane due to an earlier disturbance of rock mass along kinematically more unstable joint planes, is the inception. This has turned into a weaker plane by groundwater seepage for a very long period facilitated by drainage pattern of the area. Intense weathering features of failure zone, chert particles found from the slip surface are good indications for this factor. Furthermore, it was identified that, the shear strength of rock joints can conveniently and rapidly be determined using Rock Mass Rating System and Empirical Equations. Even though these methods provide more conservative values, results will be very useful in initial design work. Results show that the back analysis method is more reliable compared to above two but is conditional as a similar type of a failure need to occur in the same rock mass in order to employ this method. Moreover, it was revealed that Barton‟s theorem can be effectively applied for local rock masses in determining the shear strength of discontinuities and is reliable in using at lower stress levels. When considering the stability of remaining slopes of the same site, these are highly venerable for same type of failure at any moment. According to site geometrical parameters and shear strength parameters found out from back analysis reveals that the natural factor of safety is only around 1.0 for slopes that remain hanging at this site. Further, study reveals that, the most economical method of stabilizing these existing unstable areas in the site is by reduction of the slope height with the use of controlled blasting techniques. ENGINEER, Vol. 47, No. 03, pp. 49-58, 2014 Published on 2016-02-01 00:00:00
- FROM THE EDITOR…
Abstract: ENGINEER, Vol. 47, No. 03, pp. III, 2014 Published on 2016-01-07 00:00:00
- Wind Loads on High-Rise Buildings by Using Five Major International Wind
Codes and Standards
Abstract: A high-rise building of height – 183 m was employed to evaluate similarities and differences of wind load calculations done by using five major wind codes and standards. Evaluation was done in both ultimate and serviceability limit conditions. Member forces in columns, and beams, compressive stress in shear walls and support reactions obtained from finite element modelling was used to assess building responses in ultimate limit condition. Along and across wind, accelerations and drift indices were engaged to estimate serviceability limit state performances. Available 3 second gust wind speeds are converted into mean hourly and 10 minute average wind speeds to calculate wind loads on building. Wind speeds with 5 years return period was used in building acceleration calculation. The simultaneous use of higher terrain-height multiplier and importance factor may be lead to over design, even in cyclone prone areas. The use of post disaster wind speed does not exceed the drift limit but exceeds threshold acceleration value in across insert wind acceleration. ENGINEER, Vol. 47, No. 03, pp. 13-25, 2014 Published on 2016-02-01 00:00:00
- Performance and Retrofitting of Unreinforced Masonry Buildings against
Natural Disasters – A Review Study
Abstract: Un-Reinforced Masonry (URM) buildings are popular all over the world including Sri Lanka because of their durability, low cost, construction easiness and architectural character, need of less skilled labour, eco-friendliness and use of locally available materials such as ashlar or rubble, adobe and brick. However, these buildings have a higher probability of failing under natural disasters such as earthquakes, tsunamis and storm surges, floods, cyclones and landslides. In Sri Lanka, winds, landslides and floods have frequently occurred. In addition, a massive tsunami adversely affected the people in 2004 and its effects to islands on the Indian Ocean have been continued since December, 2004. Minor earthquakes have come off recently with experiences of wall cracks and no deaths. It is also believed that, there is a defused plate boundary in the making some 500 km south of the southern tip of Sri Lanka which might be the cause of these tremors or minor quakes. Further, an earthquake occurred in Colombo area in 1615, has caused around 2000 of human deaths. Therefore investigation of performance of URM buildings against these natural disasters and possible retrofitting methods are increasingly important. In this review study, an attempt is made to identify the performance of URM buildings against natural disasters and identify retrofitting methods that can be applied to existing building, to enhance the strength proper ties of structural components. Common failure mechanisms for URM structures consist of separation of walls at corners, diagonal cracking or vertical cracking in walls, separation of roofing from walls, out-of-plane wall failure, in-plane wall failure, shear cracks and de-lamination. These damages on a wall diminish the service life of building. In addition, different kinds of retrofitting methods: ferrocement, poly propylene mesh and bamboo reinforcement, for URM structures to be seismic resistant are presented. Mechanisms of failure of URM walls and effects of retrofitting techniques to reduce the damage are also discussed. ENGINEER, Vol. 47, No. 03, pp. 71-82, 2014 Published on 2016-02-01 00:00:00
- Optimization of the Accuracy of Semi-Indirect Energy Metering System
Abstract: Difference between a measurement reading and the true value of that measurement is known as accuracy. The measuring device or system should have the capability to measure and match the actual value to the quantity that is being measured to an acceptable accuracy declared by respective standards. Measurements of electrical energy in various demand categories of different utilities have their own limits. The employed measuring system is designed according to the demand category. Semi indirect metering system is being used to measure energy consumed between 42 kVA to 1 MVA by the governing Sri Lankan utility, Ceylon Electricity Board (CEB). It requires a current transformer (CT), an energy meter and lead wires only. In general, such systems are installed after certain standard checkups carried out for individual accuracy of CTs and energy meters in a standard testing laboratory. However, it has been observed that there is a considerable deviation of accuracy than expected when considering the accuracy of the whole system setup. Replacing of analogue meters by digital meters in semi indirect measuring environment to establish an automated meter reading system by a Utility has exclusive advantages such as immunity tamper up to certain extent and features supported by enhance data communication facilities etc. However, careful study is required to omit the potential of getting deviated the total system error beyond the desired limits due to the burden mismatch owing to CTs, energy meters and associated lead wires. In this research study, it was observed that considerable percentage of semi indirect metering systems installed are operating at under burden condition. The study focused to minimize the error deviation of semi indirect metering system owing to the above mentioned factors with a new concept of appropriate burden matching. The study also concentrated on to finding the factors affecting the accuracy and how to eliminate the error through a simple error compensation method. In here all the experiments were done in the laboratory for 100/5 semi indirect metering model and it describes the methodology for improving the accuracy clearly by appropriate component selection using developed charts for different contract demands operating at different power factors depending on the application.
ENGINEER, Vol. 47, No. 03, pp. 1-11, 2014 Published on 2016-02-01 00:00:00
- Airport Curbside and Parking Area Operations at BIA – Analysis of
Abstract: Airport curbside, where travelers and their baggage enter and exit the terminal, and the designated parking area are important components in airport land-side facilities. Passengers expect safe and efficient roadway operations even as volumes increase, but the design and capacity of .the curbside are often constrained by the terminal building and the proximity of on-airport land-side infrastructure. The operating characteristics of airport terminal curbside differ significantly from those of most other roadways due to several reasons such as vehicle dwell time, maneuver vehicles to and from adjacent lane, variation in demand etc. The capacity of a curbside roadway is defined both by the number of vehicles that can be accommodated while stopping to pick up or drop off passengers and the number that can be accommodated while traveling past the curbside in the through lanes. Therefore a study of operations at curbside and parking area is important to identify issues related to existing and future demand levels. The main focus of the paper is on the evaluation of vehicle operations and passenger behavior at the BIA terminal access roadway, weaving segment, arrival and departure curbside roadways and terminal car park. Analysis of vehicular traffic, travel mode choices, and curbside roadway vehicle queues, vehicle dwelling times, passenger occupancy time at curbs and passenger processing and walking times will provide useful information for developing plans for operational improvements as well as for future expansions. Using the available data, the demand and the capacity at these facilities are evaluated to estimate the existing level of service. In addition, measures were identified to improve the operational efficiency of these facilities and design improvements are proposed to ensure good operational efficiency for the forecast future demand.
ENGINEER, Vol. 47, No. 04, pp. 43-51, 2014 Published on 2015-12-11 00:00:00
- New Dynamic Battery Model for Hybrid Vehicles and Dynamic Model Analysis
Abstract: Mathematical modeling and dynamic simulation of battery storage systems can be challenging and demanding due to nonlinear nature. Simulation in time domain could be time consuming as battery storage (BS) systems do not behave according to readily available mathematical functions. Economic advantages, partial sustainability and the portability of these units pose promising substitutes for backup power systems in hybrid vehicles, hybrid electricity power generation systems, telecommunication exchanges and computer networks. Though, there have been many research papers published in this area with complex mathematical models and simulation systems, each system has its own constraints and specific applications. The aim of this research paper is to present a suitable convenient, dynamic battery model that can be used to model a general BS system. The proposed new dynamic battery model has the capability to analyse the effect of temperature, cyclic charging/discharging, and voltage stabilization effects. Simulink has been used to study the characteristics of the system and the proposed system has produced very good successful results.
ENGINEER, Vol. 47, No. 04, pp. 53-61, 2014 Published on 2015-12-11 00:00:00