Browsing by Author "Karunarathne, AMAN"

Now showing 1 - 6 of 6

item: Thesis-Abstract
DESIGN OF RIGID PAVEMENT JOINT SPACING FOR LOW VOLUME ROADS
(2016-05-02) Karunarathne, AMAN; Mampearachchi, WK
During 'the last decade, the government has given great emphasis on development of the road sector. The government also promoted the construction of concrete roads in rural areas. The major reason for this is that the rural communities can manage the construction of concrete roads as it does not require special equipments and skilled work force. Therefore the local contractors within the areas can handle the projects with the help of villagers. However, recently constructed concrete roads are having lot of defects due to poor construction. Inadequate knowledge on concrete as a road paving material is the major reason for poor construction of concrete roads in many rural areas. Concrete is a stiff material compared to the asphalt or macadam. The higher stiffness has both benefits and drawbacks. Concrete changes the volume with the thermal effect from surrounding. Effective precautions should be taken to avoid the destruction from this volume reduction. This research study was based on the simulation of volume changes and corresponding stress changes in concrete with thermal effects from surrounding. Daily variation of temperature in a slab was integrated in a finite element 'model. The finite element model was verified using a prototype slab. The verified model used to obtain the corresponding length change of the slab panel. Length change due to shrinkage of concrete pavement was obtained using the information given in BS 8110. Loa~ transfer through the propagated crack under pre-defined weaker plane was investigated in this study. The load transfer efficiency (LTE) with respect to crack opening was measured to develop a relationship between LTE and crack width. Maximum crack opening to be maintained to satisfy the specified load transfer efficiency was established based on the experimental results. The suitable joint spacing was figure out by the volume reduction of the concrete and load transfer efficiency requirement as the outcome of the research.
item: Conference-Abstract
Design of rigid pavement joint spacing for rural roads.
(Department of Civil Engineering, 2011-07) Karunarathne, AMAN; Mampearachchi, WK; Nanayakkara, SMA; Pasindu, HR
When it is compared with the flexible pavements, tensile stresses along the pavement layers are more significant in rigid pavements. Shrinkage stresses and thermal stresses are the dominant contributors to develop the tensile stresses in rigid pavements. Providing lateral joints in appropriate spacing is one of the better solutions to overcome the said stresses. Rigid pavements are usually exposed to solar radiation severely and this incorporates with the development of varying thermal stresses as well. Rate of receiving heat flux from solar radiation, thermal properties of concrete and heat loss from concrete due to convection parameters of surrounding are the main influences of the temperature variation of an exposed concrete slab. This research produces a methodology to incorporate the temperature variation of concrete slab by the use of a 3D finite element model (FEM) approach, to estimate the relevant deformation of concrete due to its exposure to the solar radiation. ANSYS (Version 12.0.1) was used for this FEM analysis, to obtain thermal variations of an exposed pavement slab. Laboratory scale slab was used to verify the results obtained from the FEM. Verified FEM is capable of producing the lateral stresses and its corresponding deformations of concrete pavement for daily thermal variation. Lateral deformations due to shrinkage effect were calculated according to the BS 8110 part 2:1985 shrinkage model. Opening of the joint crack is restricted by the load transfer requirement in consecutive pavement slabs. Aggregate interlocking is an efficient load transfer mechanism for the thin concrete pavements which are commonly used in rural roads. Effectiveness of aggregate interlocking mechanism depends on strength of the concrete, strength of aggregate, maximum aggregate size, friction of cracked surfaces, slab thickness and joint opening. Lateral joint opening vary with the pavement life and it is directly affected to the Load Transfer Efficiency (LTE). Another key aspect of this study is to carry out an experimental investigation to obtain a relationship between crack width and LTE in a rigid pavement joints. 150 mm thick test concrete pavement slab was cast with grade 25 concrete, 20 mm coarse aggregate was used to obtain the LTE at cracked joint. Standard single axel, single wheel load of 40 kN was used to simulate the tire load. From the obtained results, it was observed that LTE decreases nonlinearly with the increase of crack width. This paper describes a procedure to obtain the joint spacing for thin rigid pavements by the use of the FEM results and LTE experiment outcome. According to the study, joint spacing for rigid pavements in rural areas can be provided even beyond the specified values of ACPA.
item: Article-Abstract
Experimental Investigation of LTE in Relation to Crack Width of Non-Dowelled Joints in Concrete Pavements
Karunarathne, AMAN; Nanayakkara, SMA; Mampearachchi, WK
Dowel bar insertion and aggregate interlocking are the major load transfer mechanisms in rigid pavement joints. Aggregate interlocking is much efficient method for thin .concrete pavements. The effectiveness of aggregate interlocking mechanism depends on strength of concrete, strength of aggregate, maximum aggregate size, friction of cracked surfaces, slab thickness and crack width (CW). Some of these factors vary with the pavement life and directly affect the Load Transfer Efficiency (LTE). This paper describes an experimental investigation to obtain the relationship between CW and LTEin a rigid pavement joint. A 150mm thick concrete pavement with grade 25 concrete with 20 mm coarse aggregate was used to obtain the LTE at cracked joint. Standard single axel single wheel load of 40 kN was used to simulate the tire load. Deflection due to wheel load at either side of the joint was measured for different CWs. It was observed that LTE decreases nonlinearly with the increase of CWoFor the slab tested, LTE of 60% was obtained for CW of 2.3 mm. The results obtained from the experimental investigation can be used to design the joint spacing in nondowelled rigid pavements.
item: Article-Abstract
Non dowel joint spacing for low volume roads in tropical climate - a case study in Sri Lanka
Karunarathne, AMAN; Mampearachchi, WK; Nanayakkara, SMA
Shrinkage and thermal stresses are the dominant contributors to develop tensile stresses in rigid pavements. As a result, cracks can be developed in pavement without vehicle loading. Providing lateral joints at appropriate spacing is one of the solutions to overcome the said stresses. Width of a joint will be wider at the time when curling and contraction strains are at the optimum strain. It is essential to consider daily temperature variation, shrinkage and curling together with the fatigue damage in determination of optimum joint spacing for concrete roads. Rigid pavements are usually exposed to solar radiation to a great extent and as a result thermal stresses are developed. This research propose a methodology to estimate the relevant deformation (width of the joint) of concrete due to its exposure to the solar radiation incorporate the temperature variation of the concrete slab by use of a 3D finite element model (FEM) approach. A laboratory scale slab was used to verify the results obtained from the FEM. Lateral deformations due to shrinkage effect were calculated according to the American Concrete Institute shrinkage model (ACI 209 R-92). Aggregate interlocking is an efficient load transfer mechanism for thin concrete pavements which are commonly used in rural roads. An Experiment was carried out to find a relationship between crack width of the interlocking joint and load transfer efficiency (LTE). From the obtained results, it was observed that LTE decreases non-linearly with the increase of crack width. According to the study, joint spacing of thin rigid pavements can be provided even beyond the specified values of American Concrete Pavement Association (ACPA) to maintain 60% of LTE.
item: Conference-Extended-Abstract
Review the guidelines of overlay design for flexible pavements
(2009) Karunarathne, AMAN; Mampearachchi, WK
This primary objective of this research is to compare the overlay design guidelines and verify the feasibility of them on Sri Lankan road network. This is focus on overlay design procedures for the flexible pavements. The study included the collection of required traffic and deflection data in several categories of Sri Lankan road network. Deflection data is needed to obtain the remaining structural capacity (Effective Structural Number- SNeff) of the pavement and can be collected through the related departments in Sri Lanka. Sub-grade strength parameters were found using the field and lab CBR (California Bearing Ratio) experiment. The main advantage of this comparison is to identify the most suitable design procedure of required structural overlay thickness according to the several traffic categories of traffic in Sri Lankan road network.
item: Conference-Abstract
Simulation of thermal behavior of ground concrete slab exposed to solar radiation
(Department of Civil Engineering, University of Moratuwa., 2010) Karunarathne, AMAN; Mampearachchi, WK; Nanayakkara, SMA; Pasindu, HR
Rate of heat flux from solar radiation, thermal properties of concrete and heat loss from concrete due to convection parameters of surrounding influence the temperature variation of an exposed concrete slab. Literature review has shown that a wide range of views on heat generation in concrete during the setting time and early age. This paper describes a method to incorporate the temperature variation of a concrete slab due to solar radiation to estimate the relevant deformation of concrete using finite element model (FEM) approach. Variation of the temperature profile across a slab is well known fact and it cause differential thermal stresses and differential deformation of concrete structures. These stresses are very savior in rigid pavements in tropical countries. Deformation of slabs and pavements can lead to structural failures, efficiency drop downs, etc. Pre determination of ultimate deformation is important to taking relevant precautions. ANSYS version 12 used to develop the FEM which was verified by a laboratory scale slab. It is one of the best non-linear analysis software to illustrate the thermal behavior of concrete. FEM gives temperature values at each location and hence the deformation also can be obtained. Prototype model constructed and measured the daily temperature variation at various points. Temperature profile at the centre was measured by thermocouples set across the thickness. Temperature variations were compared in the same points in FEM and the prototype for the verification. The research provides a verified method to obtain temperature values at any location in a concrete slab which exposed to solar radiation. The deformation values at the particular locations can be obtained from FEM for varies thicknesses. Outcome is important in designing of expansion joints and load transfer non-dowelled joints in rigid pavements. Amount of curling and warping of pavements can be obtained using the FEM for varies lengths. The FEM approach is very helpful for proper designing of rigid pavements with less faulting, cracking and other distresses.