Browsing by Author "Galappaththi, GS"

Now showing 1 - 3 of 3

item: Conference-Abstract
An approach to estimate the vehicle travel time on un-signalized two lane roads
(Department of Civil Engineering, University of Moratuwa., 2014-08) Galappaththi, GS; Perera, L; Bandara, JMSJ; Pasindu, HR
Reliable travel time estimation for a given route is important in transport planning. Even though the developed countries in the world have different methods of forecasting travel time from a simple road network to a complex transport network, local availability of such methods are lacking mainly due to the inadequacy of data or investments for the implementation. Several qualitative factors such as geography, weather, time of travel etc. and quantitative factors such as road geometry, traffic flow etc. affects the time taken to travel. But the fluctuations in these factors cause significant changes in the travel time. There are no any travel time estimation models currently used in the country during the planning stage or in the monitoring stage to check the efficiencies or enhance the current conditions of the road network. The objective of this study is to develop a relationship using different land use patterns to estimate the travel time on three leg intersections accurately for road links in order to build a model for travel time estimation on un-signalized two lane roads. Trip attraction and trip generation in regions depends on the land use pattern of that area and cause the differences in vehicle travel. Due to this reason this study focus to develop a travel time estimation technique that can be implemented by considering different land use types such as residential, commercial, industrial, accessibility, agricultural/forest coverage etc. Two lane road sections of three national highways in Sri Lanka; Peliyagoda-Puttalam road (A03), Colombo-Kandy road (A01), Ambepussa-Trincomalee road (A06) were considered for this study to associate the different land use types, different vertical and horizontal alignments and its correlation with vehicle travel times. For this study, travel time data along the roads was collected during peak hours of the day using a GPS (Global Positioning System) data logger. Time taken to travel, Travel length, presence of commercial length, additional number of access roads ( access roads present other than intersection connection roads) and number of schools or temples in the intersection were collected for each intersections. Multivariate regression analysis is used to develop the relationship between the land use pattern and the travel time. The model showed a significant positive correlation with Travel length and Commercial length present.
item: Thesis-Full-text
Estimating travel time for un-signalized two lane highways in Sri Lanka
Galappaththi, GS; Bandara, JMSJ
Travel time estimation is an important parameter in effective transport planning, quality maintenance, and traffic management. Even though several models are available worldwide for travel time estimation from simple road network to a complex transport network, local availability of such methods are lacking mainly due to the inadequacy of research, data and resources. Travel time along a particular route is associated with several factors including land use type, geography, weather, road condition, traffic flow, road geometry. One or a combination of these factors can cause variation in travel time and the effect from each parameter can change with the land use activities in the area. The objective of this research is to develop a relationship to estimate the travel time for road links to monitor the travel time and of two lane highways without signalized intersections in Sri Lankan context, by assessing the correlation between land use type and the travel time along the road. Two lane road sections of three national highways in Sri Lanka; Peliyagoda-Puttalam road (A03), Colombo-Kandy road (A01), Ambepussa-Trincomalee road (A06) were considered for this study to associate the different land use types, different vertical and horizontal alignments and its correlation with vehicle travel times. Continuous travel time data along the roads was collected during daytime using GPS (Global Positioning System) data loggers. Road was sectioned according to the land use type. Multivariate stepwise regression was used to develop the relationship between the land use type and the travel time. Land use data showed significant positive correlation with the travel time data. One travel time estimation model for three leg un-signalized intersections and four models for travel time estimation for different four land use types, commercial, residential present on both side, residential present on one side and cultivation for the stretch of the road were successfully developed with model fit more than 69% and Mean Absolute Percentage Error (MAPE) of more than 38%
item:
Evaluation of the potential for delayed ettringite formation in concrete
(2015-05-29) Dayarathne, WHRS; Galappaththi, GS; Perera, KES; Nanayakkara, SMA
Delayed ettringite formation (DEF) is commonly referred to as heat-induced internal sulfate attack, which affects the durability and strength of the concrete like in alkali–silica reaction (ASR). Several researches have been done to identify the factors governing DEF and to quantify the effect and also to provide necessary prevention methods. However, most of the factors are yet to be investigated and quantified. It is evident that when fly ash is present, the risk of formation of delayed ettringite is low but its behavior with different types of cement have not been found out yet. DEF is long term deterioration in concrete and for effects of DEF to appear in actual structures may take 2 - 20 years. There is no standardized accelerated method of testing cement- aggregate combinations for premature deterioration due to DEF but there are test methods proposed by several researchers. This paper presents an evaluation of potential of DEF for different cement types available in the local market based on FU’s Method. In this method, expansion of mortar bar specimens (25mm × 25mm × 285mm) is monitored after specimens are subjected to specified heating and drying cycles. Evaluation of DEF was carried out for Ordinary Portland Cement, Portland Limestone Cement, Fly Ash Blended Cement and Triple Blended Cement. It was found that there is a significant effect of cement type on DEF. Further it was found that the potential for formation of delayed ettringite is less with partial replacement of OPC with supplementary cementitious materials such as fly ash. Furthermore it has been revealed that the risk of formation of DEF in fly ash blended cements is less than in Ordinary Portland cement and Portland limestone cement. It was also found that the influence of coarse aggregate phase on expansion due to DEF is significant.