TRF - 2022

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Browsing TRF - 2022 by Subject "Cost"

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    item: Conference-Abstract
    Implementation of warm mix asphalt in Sri Lanka: case study
    (Department of Civil Engineering, University of Moratuwa, 2022-12) Gunarathna, S; Mampearachchi, W; Langappuli, S; Hettiarachchi, C; Weerakoon, J; Ranasoma, I; Perera, HLK
    Warm Mix Asphalt (WMA) is the technology that allows a reduction in the production and paves temperature of Asphalt. WMA can be produced using four different technologies; chemical additives, organic additives, water-bearing additives and water-based processes. Adaptation of WMA may reduce the production cost, paving cost, and emission of greenhouse gases and allow longer paving season. Therefore, implementation of WMA in Sri Lanka is vital as WMA can be an answer to the economic crisis and has been recognized as the future of Asphalt. Organic additive technology or chemical additive technology was decided to select for the implementation of WMA in Sri Lanka as the minimum plant modifications in these technologies. Sasobit®, which is an organic WMA additive, was selected for the implementation as it is available in the south Asian region, and further, this was successfully implemented in India. Sasobit® is a synthetic wax which decreases the viscosity of the bitumen in lower temperatures. However, below 900C, Sasobit® creates a crystalized lattice structure allowing the modified bitumen to stiffen and increase the rutting resistance. The optimum Sasobit® percentage was determined as 2.5% by mass of binder by analyzing the results of viscosity against the Temperature curve. A Series of samples with bitumen modified by optimum Sasobit® percentage shall be prepared in different mixing temperatures and different compaction temperatures falling under the WMA temperature range. The mixing temperature and compaction temperature shall be selected where the optimum density was achieved, and results are within the limitations stated in ICTAD specifications for Marshal Test. The mixing temperature was found as 1400C, and the compaction temperature was 1300C. The section selected for the study is 500m in Mawanella. A paving trial was conducted near the selected study area for 57 m, and it was observed that the required degree of Compaction was achieved with lower roller compaction coverage. The bitumen decentering plant was modified to achieve the modification by Samsonite®. Bitumen was circulated through the plant for 2 hours after Sasobit® was added, and the temperature was maintained at 1400C. The mixing of Asphalt was maintained at 1400C, and the Compaction at the field was started when the temperature was 1300C. One breakdown roller coverage was able to be reduced, and four intermediate roller covers were ably reduced from typical roller coverage, and still, the required degree of Compaction was achieved. Further, it was observed that the temperature drop to 600C in the WMA is 120 minutes (2 hours). Temperature is lowered in WMA bitumen production by 10- 150C allowing cost saving duet lowered use of fuel in heating of materials. Further, the required degree of Compaction was achieved by lower roller coverage. Moreover, the road can be open to traffic less than 2 hours from the time of the paving. Therefore, the paving season can be increased /which is beneficial for roads with heavy traffic flow. Implementation of WMA in Sri Lanka is vital at this stage, and it is evident WMA can be used as absolution for the current economic crisis. However, there are more options for modification methods, and the use of recycled Asphalt is more feasible in WMA. Hence, it is recommended to study more along these avenues.
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    item: Conference-Abstract
    Model to identify the optimum feeder bus route for an urban rail transit station based on capacity of feeder buses
    (Department of Civil Engineering, University of Moratuwa, 2022-12) Kanagasingam, U; Bandara, S; Perera, HLK
    Urban rail transit systems are very cost-effective as compared to other transit modes though they cannot provide wider service coverage for the users. Feeder buses play a major role in filling the service gaps left by urban rail transits. The effectiveness of the feeder bus of an urban rail transit depends on its bus route length, frequency, capacity, and travel time. As all parameters are interconnected, changing one will impact others. This study discusses a mathematical model to identify the optimum feeder bus route for an urban rail transit station. The effectiveness of the feeder bus can be optimized by reducing the total cost of /the feeder bus service. The total cost includes both the user's costs and the operator's costs. Several service parameters influence the components of the total cost equation. The parameters discussed in this study are route length, frequency, bus capacity, travelling and waiting times, walking distance and passenger behaviour characteristics. Assumptions were made regarding passenger behaviour because it varies for every passenger according to several factors. For example, bus stop spacing and maximum walking distances were assumed to be constants, and all roads were assumed to be in grid mesh format. First, a simple model was developed that has one trip generated to the railway station. Then it is further extended to one bus stop from which several trips are directed to a railway station. After that, a model that has several bus stops in a feeder bus route that connects to a railway station was developed. From there, an optimized many-to-one feeder service model was identified. In different instances, there will be changes in the values of the parameters in the mathematical model. By using the mathematical model, we can check which set of parameters best suits the optimized route. This can be further extended to a many-to-many demand model that has several railway stations and bus stops that are interconnected with each other.