Browsing by Author "Fernando, PRD"

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item: Conference-Abstract
Application of dynamic traffic assignment and determine model parameters for urban traffic conditions in Sri Lanka
(Sri Lanka Society of Transport and Logistics, 2020-11) Prasanga, HN; Fernando, PRD; Gunaruwan, TL
The travel behaviour of people on a road network is not often constant and it changes over the time. Drivers who use a particular road network continuously tend to find more comfortable, congestion free routes with least travel time to reach their destinations. This scenario is complicated in the context of a congested and high-density urban road network where drivers have more freedom to use alternative paths to reach their destinations based on changing traffic patterns within short periods. Further, the presence of navigational tools such as Google Maps help the drivers in making quick decisions in selecting congestion free routes, making route selection more dynamic. In order to address this dynamic environment, many microsimulation traffic models around the world have developed the dynamic traffic assignment tool which provides the traffic modeller a more realistic modelling environment for urban traffic over the conventional static route assignment. Further, conventional static route assignment may not be able to simulate and give realistic results for urban areas with complex route networks. However, this facility available in the microsimulation traffic models has not yet been tested under Sri Lankan conditions. Therefore, the objective of this study is to test the dynamic traffic assignment process and find the model parameters that are compatible with Sri Lankan traffic conditions and driver behaviour. For this purpose, PTV Vissim traffic microsimulation software was used. A 2.5 km stretch of A 000: Kollupitiya-Sri Jayawardenapura road and its vicinity (comprising Rajagiriya junction and flyover) have been considered for the case study. Manual vehicle number plate surveys were carried out at 14 predefined locations covering the entire area to develop origin-destination matrices for different vehicle classes. The average growth factor method was used to develop working matrices from the sample matrices developed through this number plate survey. The origin destination matrices developed for the period between 5.00 pm and 6.00 pm were used as the input for the traffic model. Stochastic (Kirchhoff) traffic assignment method was used to distribute traffic between zones in Vissim. Model convergence, calibration and validation were carried out as per the Vissim manual and Traffic Modelling guidelines developed by Transport for London Institute. The GEH static values of input and output flow values of the modelled network were used as the parameters for model calibration and validation. The road network developed in Vissim was successfully calibrated to local conditions and a set of model parameters that were compatible with Sri Lankan conditions found. However, there is a need for future research work to find model parameters that are compatible with different road and traffic conditions.
item: Conference-Abstract
Effects of super pave specifies aggregate gradation on Marshall mix parameters
(Department of Civil Engineering, University of Moratuwa., 2010) Fernando, PRD; Mampearachchi, WK; Pasindu, HR
Standard specification for roads and bridges (SSCM) includes gradation master band in which upper and lower percent passing has been specified for most sieve sizes. These limits tend to make finer gradation in the asphalt concrete than Superpave specifies aggregate gradation. The objective of this research is to evaluate the effect of Superpave aggregate gradations on Marshall Mix parameters (heavy traffic condition) while types of asphalt binder and type of aggregate remain unchanged The method was very similar as Marshall Mix design procedure that SSCM are described for Sri Lankan conditions, except Superpave guides was used to develop the design-blended aggregate envelops. Locally available crushed granite and 60-70 penetration grade bitumen were identified and collected to prepare different test samples. Individual properties of asphalt binder and aggregate were tested to determine that they are met relevant specifications as mentioned in SSCM. The different hot bin aggregate samples were combined to make aggregate mixtures that comply with the Superpave conditions. The coarse side (plus 4.75 mm) of the grading curve remained almost unchanged, while the fine side (minus 4.75 mm) was varied in order to pass through, above, and below the restricted zone specified in superpave aggregate gradation. The blended aggregate envelopes were categorized as follows:  Over Restricted Zone (ORZ) with comply to control points.  Through Restricted Zone (TRZ) with comply to control points.  Below Restricted Zone (BRZ) with comply to control points. It was observed from the research that all Superpave specifies aggregates blends were satisfied the SSCM specified Marshall Criteria. Superpave restricted zone was not affected on Marshall criteria under local conditions and specifications. Optimum binder content (OBC) and Binder Tolerance (BT) were reduced when aggregate blend becomes coarser. Average Film Thickness (AFT) was increased when aggregate blend become coarser. Further, Marshall Stability and Void in Mineral Aggregate (VMA) are not any significance differences when compare three gradation envelops (ORZ, TRZ & BRZ). There was no significance different of Marshall Flow of ORZ & TRZ, while BRZ showed some lesser value than ORZ & TRZ. Air Voids (Va) value was increased when the aggregate blends become coarse.
item: Thesis-Abstract
Effects of superpave specifies aggregate gradation on marshall mix parameters
Fernando, PRD; Kumara, MAW
The purpose of this study is to evaluate the effect of the Superpave aggregate gradation on Marshall Parameters. The Superpave Specifies aggregate gradation was used to select aggregate gradation as such blending of available aggregate was carried out and that the gradations were above, through and below the Superpave restricted zone. The Marshall method was used to design the asphalt mixtures. Asphalt concrete mixes were designed for 28 numbers of Superpave aggregate gradations and were tested in the laboratory to evaluate their stability and flow value. In addition, density - void analysis was carried out to find Marshall Parameters. Statistically, all type of mixes (over, through and above the restricted zone) did not show any significant difference on Marshall Stability and Void in Mineral aggregate (VMA) in this study. The gradation pass below the restricted zone, those mixes showed higher Va and lesser Flow value than the gradation pass above / through the restricted zone. Based on the testing perfonned In this study, following recommendations can be made; 1. Superpave specifies aggregate gradation could be used as a guide to develop 100 percent crushed granite aggregate blends for wearing course. 2. Superpave coarser aggregate gradation (gradation that pass through or below the Superpave restricted zone) could be used as wearing courses with local conditions (still not use such a gradation for wearing coarse in Sri Lankan specifications) .
item: Article-Abstract
Evaluation of the effect of superpave aggregate gradations on marshall mix design parameters of wearing course
Mampearachchi, WK; Fernando, PRD
The purpose of this study was to evaluate the effect of the Superpave specified aggregate gradation on Marshall mix design parameters. Twenty eight (28) asphalt concrete mixtures were prepared in three types of gradations such that the gradations were above, through and below the Superpave restricted zone. Samples were prepared for Marshal mix design and tested in the laboratory to evaluate the Marshall stability, flow and volumetric properties. Statistical analysis showed that all three types of mixtures, above, through and below the restricted zone, did not have any significant difference on Marshall stability and void in mineral aggregate (VMA). The mixtures with gradation passing below the restricted zone showed higher air voids (Va ) and lower flow values than gradation passing above and through the restricted zone. The results indicated that Superpave specified aggregate gradation could be used as a guide to select aggregate gradations for wearing courses. Aggregate gradation below the restricted zone requires 0.5 % less bitumen than typical mix designs and has a lower binder tolerance limit. Keywords: Aggregate gradation, Marshall parameters, restricted zone, Superpave gradation, wearing course.