Effect of Pavement Stiffness on the Shape of Deflection Bowl/ A pályaszerkezet merevségének hatása a behajlási teknő alakjára (original) (raw)
Related papers
Effect of Pavement Stiffness on the Shape of Deflection Bowl
2015
The paper introduces a new method for calculating the elastic moduli of pavement layers. The method requires only two input parameters: the thickness of the upper "bound" layer and the Falling Weight Deflectometer (FWD) or Improved Benkelman Beam Apparatus (IBBA) measurement data. The authors developed a continuously differentiable regression function, which can be applied to describe the shape of the deflection bowl. Additional parameters of the deflection bowl (e.g. radius of curvature, position of inflexion point) can be calculated based on the regression function. FWD measurements were simulated running the BISAR (Bitumen Stress Analysis in Roads) software on different pavement variations. Outputs of the simulations were further processed with self-developed software. As a result, a series of diagrams were elaborated, by which the elastic moduli of the pavement layers can be determined. Stiffness / pavement layers / elastic moduli / deflection bowl / BISAR Kivonat-A pályaszerkezet merevségének hatása a behajlási teknő alakjára. Útpályaszerkezetek esetében a megfelelő rehabilitációs eljárás kiválasztása igen nagy gazdasági jelentőséggel bír. Ezért a szerkezetek állapotának megfelelő ismerete nélküli döntéshozatal igen költséges lehet. Emiatt különösen fontos, hogy az FWD (Falling Weight Deflectometer) vagy IBBA (Improved Benkelman Beam Apparatus) eszközzel mért elmozdulások elemzésével olyan többletinformációhoz jussunk, ami a döntést megkönnyíti a gyakorló mérnök számára. Az FWD vagy IBBA eszközzel mért deformációs vonalra illesztett függvényből levezetett görbületi sugár (R 0) és a burkolatvastagság (h) ismeretében a kötött rétegek alján jelentkező megnyúlásokat jól lehet becsülni. A BISAR (Bitumen Stress Analysis in Roads) programmal végzett számítások statisztikai elemzése pedig azt mutatja, hogy a D 0 (központi behajlás) és R 0 (görbületi sugár) paraméterek ismeretében lehetőség nyílik a kötött és szemcsés rétegek modulusának visszaszámolására. Merevség / pályaszerkezet rétegek / rugalmassági modulus / behajlási teknő / BISAR
Application of deflection bowl parameters for assessing different structures of road pavement
MATEC Web of Conferences, 2018
To date, non-destruction testing (NDT) method is the most popular method to assess the condition of road pavement. Among all evaluation procedures of the NDT method, load-deflection backcalculation analysis is one that is developed widely to understand the structural behavior of road pavement. On one side, the use of this analysis is greatly beneficial for presenting the layer characteristic accurately. However, the analysis requires specialist expertise. To overcome this, deflection bowl parameter application could become one alternative. The parameters are very easy to use; however, the intention of the parameters so far is only as an indication of the condition of the structural layer of the road pavement. Therefore, the parameters have to be used with careful consideration. In this study, the parameters were evaluated to determine the optimal usage of the parameters against different structures of road pavements. The results showed that a simplification of the number of paramete...
FALLING WEIGHT DEFLECTOMETER BOWL PARAMETERS AS ANALYSIS TOOL FOR PAVEMENT STRUCTURAL EVALUATIONS
The falling weight deflectometer (FWD) is used world wide as a well established and valuable non-destructive road testing device for pavement structural analyses. The FWD is used mostly for rehabilitation design investigations and for pavement management system (PMS) monitoring on a network basis. On project level investigations, both design charts and mechanistic approaches using multi-layered linear elastic theory and back-calculation procedures are often used to provide structural evaluations and rehabilitation options. As an alternative to this a semi-mechanistic semi-empirical analysis technique has been developed in South Africa whereby new deflection bowl parameters measured with the FWD used to give guidance on individual layer strengths and pinpoint rehabilitation needs. This approach is fully suited to supplementary analysis of FWD data in the Australian design systems, and overcomes some of the limitations of the curvature parameter. This paper briefly describes the current practice and basis of this use of deflection bowl parameters, and illustrates the use with a current pavement rehabilitation project underway in South Africa.
Most of the road network in India has a significant level of deterioration and therefore requires major rehabilitation projects; in general, most of these rehabilitation activities involve a new asphalt layer on the original pavement structure; knowledge and analysis of structural capacity of the pavement is essential to perform a durable and economical rehabilitation design. The determination of the structural capacity of flexible pavements as a function of the deflections produced by the application of a load. The techniques most used in many countries to measure pavement deflections are the Falling Weight Deflectometer (FWD) and the Benkelman beam, the first one works under dynamic loading and the second device under static loading. The use of devices under static loading has not been recommended by several design methodologies, including AASHTO, but these are still used widely in many countries including India, for this reason it is necessary to compare the deflections by Benkelman beam and falling weight deflectmeter. In this study deflections measure by BBD and FWD techniques on 30 deflection observation points on selected 1.5 km flexible urban highway stretch. Both test are perform simultaneously on marking points. And data collected by booth test are as per IRC: 81-1997 and IRC: 115-2014.
IPTEK Journal of Proceedings Series
Falling Weight Deflectometer, FWD, is the most popular equipment used to measure the deflection of flexible pavement in Indonesia. The loading used during application of the FWD equipment generally correlates directly with those of the loads of standard heavy vehicles. Therefore, the resulted pavement deflections obtained from the tests should be also suitable for highways traversed by standard normal vehicles only. This may not be the case for highways in Indonesia, where most trucks are highly overloaded, so much beyond the allowable standard loads. The existing method of FWD test may not be representative anymore to measure the actual pavement deflections under highly overloaded vehicles. In this paper, the authors describe their findings about deflections of flexible pavement when the pavements were subjected by heavily overloaded vehicles. The first step is to modify the FWD equipment with larger falling distances and heavier loads to simulate the highly overloaded vehicles in Indonesia. Based on the results and by using statistical approach, a new mathematical equation can be derived to reflect the functions of actual pavement deflections under much higher loads when compared to those of standard normal load. Therefore, using this new equation one can predict the actual pavement deflection under highly overloaded vehicles, by just performing standard FWD test of standard loads on the pavement, so that the design of overlay thickness can be modified accordingly to be applicable to overloaded traffic in Indonesia.
International Journal For Science Technology And Engineering, 2017
Most of the road network in India has a significant level of deterioration and therefore requires major rehabilitation projects; in general, most of these rehabilitation activities involve a new asphalt layer on the original pavement structure; knowledge and analysis of structural capacity of the pavement is essential to perform a durable and economical rehabilitation design. The determination of the structural capacity of flexible pavements as a function of the deflections produced by the application of a load. The techniques most used in many countries to measure pavement deflections are the Falling Weight Deflectometer (FWD) and the Benkelman beam, the first one works under dynamic loading and the second device under static loading. The use of devices under static loading has not been recommended by several design methodologies, including AASHTO, but these are still used widely in many countries including India, for this reason it is necessary to compare the deflections by Benkelman beam and falling weight deflectmeter. In this study deflections measure by BBD and FWD techniques on 30 deflection observation points on selected 1.5 km flexible urban highway stretch. Both test are perform simultaneously on marking points. And data collected by booth test are as per IRC: 81-1997 and IRC: 115-2014.
REVIEW OF FALLING WEIGHT DEFLECTOMETER FOR ASSESSMENT OF FLEXIBLE PAVEMENT
ELK ASIA PACIFIC JOURNAL OF CIVIL ENGINEERING AND STRUCTURAL DEVELOPMENT , 2018
Fast development of road networks has become a trend in India and everywhere in the world. From the past couple of decades, it has been observed that numerous highways are in a phase of deteriorations. Identifying the reasons for deteriorations requires a pavement evaluation study. Many performances study have been made out by exploring flexible pavements, by the users of widely accepted falling weight deflectometer (FWD) as a non-destructive test (NDT) and considered it as a standard for structure assessment. The primary objective of this study is to a review of an FWD instrument and the also study of the empirically derived methods and a back calculation process for computing layer moduli and factors influencing it. The essential need of correction factors to get reliable layer moduli is an also discussed, in addition to the investigation of advancement of low-cost indigenous FWD models flexible pavements, by the users of widely accepted falling weight deflectometer (FWD) as a non-destructive test (NDT) and considered it as a standard for structure assessment. The primary objective of this study is to a review of an FWD instrument and the also study of the empirically derived methods and a back calculation process for computing layer moduli and factors influencing it. The essential need of correction factors to get reliable layer moduli is an also discussed, in addition to the investigation of advancement of low-cost indigenous FWD models
Young’s Modulus and Deflection Assessment on Pavement Using a Lightweight Deflectometer
International Journal of GEOMATE, 2021
This research implemented direct assessment in the field on road structures using the Light Weight Deflectometer (LWD) method. This method is similar to the Falling Weight Deflectometer (FWD) method. The LWD method uses a lower loads compared to the FWD method. LWD method was chosen because the equipment is quite portable and straightforward allowing it to be used directly in the field, making inspection easier. The LWD method is more suitable for assessing the pavement conditions in which the volume of road use is not too high. This study aims to determine the value of the road structure conditions based on material properties. The location of the survey was Kupang City, East Nusa Tenggara, and Indonesia. The number of test points is 77 main points, with each point consisting of several tests. The test results obtained in this study are the value of deflection and modulus of elasticity at each test point. In addition, a radius of curvature analysis was carried out to determine the base of the pavement structure conditions. LWD testing by giving a load on the surface of the pavement was found to predict the base conditions of the road structure. This study also analyzes the EFWD conversion value from the ELWD test results and the correlation between these methods is presented.
EVALUATION OF RIGID PAVEMENTS BY DEFLECTION APPROACH
Since 1951 there has been a sevenfold increase in the Indian road network while the traffic has increased 120 times. This leads to the deterioration of the surface of the pavements. Deterioration of pavements may be functional or structural in nature. Evaluation and timely assessment of pavement condition will help to judge the necessary steps to be taken to improve pavement conditions. Pavement surface deflection measurements are one of the primary means of evaluating a flexible pavement structure. 'Benkelman Beam Deflection (BBD) Technique is used to find out the characteristic deflection for flexible pavement. The testing and analysis by BBD technique finally provides us with overlay thickness in terms of Bituminous Macadam. The use of BBD technique may not be only limited to evaluate flexible pavements. Evaluation of newly constructed rigid pavements on the basis of Load Transfer Efficiency of dowel bars gives an idea of the overall performance. The accuracy of evaluating load transfer efficiency (LTE) of joint is important to estimate whether the dowel is disabled or not. The ratio of the edge deflection of unloaded slab to the edge deflection of loaded slab is used as index to evaluate LTE of joint. The objective of this paper is to find out the utility of Benkelman Beam Deflection Test on rigid pavements. In this paper based on the known deflection relationship between loaded and unloaded slab calculated with the help of two Benkelman beams which is a technique generally used to determine the overlay thickness for flexible pavements. A rigid pavement road stretch (Swami Vivekanand Road) constructed 2 years ago in Pune city was evaluated using BBD technique. Deflections measured on slabs (loaded slab and unloaded slab) across the dowel bars would give a measure of the load transfer efficiency of the dowel bars.
In Ethiopia the failure of roads are before handover period. Most roads found in Ethiopia are flexible pavements. Nowadays, the failure of surface of flexible pavement roads are common before the expected design period. For the example Bako-Nekemte road/ has become a critical issue in our country. The most common parameters that cause stress, strain and deflection of the roads are loads and pressures that come from vehicles. Moreover, modulus of elasticity, Poisson's ratio and thickness of each layer needs to be characterized. Further, the load magnitude, contact pressure (or load radius) and location are defined for each load (wheel) considered. Finite element method (FEM) is a numerical analysis technique to obtain the stress-strain and deflection of each pavement layers. Analytical method usually uses layers thickness, loads, elastic modulus and Poisson's ratio of the pavement materials as design parameters. The objective of this research was to study the sensitivity of the road parameters in analyzing the major causes of failure in asphalt pavement layers fatigue cracking and rutting deformation which came due to the critical tensile strains at the bottom of the asphalt layer and the critical compressive strains on the top of subgrade using the finite element method by relating the standard specification of ERA and laboratory test result. This thesis studied the analysis of stress-strain and deflection of flexible pavements using Everstress finite element method. The Ever stress program will take into account any stress dependent stiffness characteristics. This thesis dealt with ways to reduce deflections by varying the design configuration, such as increasing the HMA modulus, the base modulus, sub base modulus, the subgrade modulus and increasing thickness of each layers. Based on type of materials to use the value of elastic modulus and poison's ratio are various in each layers, in layer 1 is varied from 1500 to 3500 MPa, in layer 2 is varied from 200 to 1000MPa, in layer 3 is varied from 100 to 250 MPa and in layer 4 is varied from 20MPa to 150MPa.