There are various overlay design methodol ogies in vogue now and among which at least three basic approaches may be identified as follows. The design traffic in terms of cumulative standard. In the bbd technique overlay design is based on computed. Bbd analysis tool calculate characteristic deflection.
Strengthening and extension of existing urban road for the. This study took as it basis an assessment of the stress and strain distribution in the pavement layers to the materials failure envelope using kenpave software. Introduction and design of flexible pavement overlay 15. Structural overlay design using ndt methods road surface. As improving overlay control is crucial to yield learning in hvm fabs, we investigated deploying an inline ebeam overlay metrology using a sem scanning electron microscope as a reference metrology for inline optical. The slope or deflection differences close to the load such as radius of curvature r, shape factor f 1, and surface curvature index sci. Overlay design by benkelman beam free download as powerpoint presentation.
Ii compliance certificate this is to certify that research work embodied in this thesis entitled strengthening and widening of flexible pavement. Fwd and benkelman beam deflection bbd are prominent techniques in india for strengthening and. Effective thickness approach deflection approach mechanistic approach. It carries out back and forward analysis within the one program, originally using the odemarkboussineq transformed section. A comparison of the predicted and measured distresses is also presented for two ac overlay design projects. Bbd analysis software to calculate benkelman beam deflection and calculate. Electronic upgrade of a standard benkelman beam to enable. In developing countries like india most of the overlay design of pavements was done by using static method like benkelman beam deflectometer. This definition appears rarely and is found in the following acronym finder categories. Shinkar assistant professor and pg incharge civil engineering department atmiya institutes of technology and science. This has been attempted several times in the past but resulting devices were often complex and expensive. Benkelman beam, design, fwd, falling weight deflectometer, non destructive testing.
Nondestructive deflection testing based mechanistic. The most widely used method in india has been benkelman beam deflection bbd method. The benkelman beam measures the deflection of a flexible pavement under moving wheel loads. Benkelman beam deflection studies linkedin slideshare. Structural overlay design using ndt methods free download as pdf file. Benkelman beam, dynaflect, falling weight deflectometer. Oct 21, 2019 the bbd module is used for individual analysis of bbd benkelman beam deflection. Fwd data is primarily used to estimate pavement structural capacity for 1 overlay design and 2 to determine if a pavement is being overloaded. The design is checked by software iitpave for horizontal tensile strain computed at bottom of bituminous layer and vertical strain at top of subgrade. A thesis submitted to gujarat technological university in. Benkelman beam for flexible pavement deflection testing. The benkelman beam, instrumented for automatic recording of the full bowl shape. Deflectometer rdd, benkelman beam deflectometer bbd.
Deflection should be find out by benkelman beam deflection test. Overlay design for a given section is based not on individual deflection values but on a statistical. This program, if incorporated with pavement deflection measurements. The bbd module is used for individual analysis of bbd benkelman beam deflection. Measures the deflection of a flexible pavement under moving wheel loads. Chapter eight applications of falling weight deflectometer. Overlay design of low volume road using light weight.
First 500 m section dial gauge reading data of benkelman beam survey on stretch are shown in above table and other data shown in data analysis chapter. Highway development and management tool, hdm4 software, developed by the world bank f or. The overlay process in revu lets you compare two or more pdfs by converting each document to a different color and stacking them on top of each other as layers in a new pdf. Evaluation of layer moduli and overlay design is supplied by dynatest.
Alternate material can be used in the pavement designing. Benkelman beam deflection technique and related to the pavement performance. Using falling weight deflectometer data with mechanisticempirical design and analysis, volume i. Structural overlay design of flexible pavement by nondestructive test methods in louisiana zhong wu, xingwei chen, kavin gaspard and zhongjie zhang abstract the louisiana department of transportation and development currently uses empirical book values in the overlay thickness design. To determine the bearing capacity and deflection of subgrade and subbase of roads. Part ii of this report presents the recommended testing procedures, equipment, and personnel requirements for conducting the benkelman beam test. Benkelman beam conducted under washo method to collect data in order to find deflection condition of existing pavement.
Field data from either the fwd or instrumented benkelman beam may be used, and the program will apply one or two loading circles accordingly. Benkelman beam deflection method for evaluation of structural capacity of existing flexible pavements and design of overlay phase 1 this paper reports on the first phase of a study of the benkelman beam method, sponsored by the indian ministry of surface transport. A falling weight deflectometer fwd is a testing device used by civil engineers to evaluate the physical properties of pavement. The benkelman beam device is based on level arm principles, where the tip of the device is placed between the dual tires of a single axle loaded to 80 kn 18,000 lbf, and the tires are inflated to 480 to 550 kpa 70 to 80 lbfinch 2 see figure 2.
Pavement deflection measurement my assignment tutor. A case study of rajkotmorbi sh 24 was carried out by mr. Other pavement design software can be used for evaluation. Effective thickness method basic concept thickness of overlay is the difference between the thickness required for a new pavement and the effective thickness of the existing pavement. As part of a pavement management system, supplementing the visual assessment of pavements, deflections by benkelman beam have been utilised for both the design of rehabilitation methods and their effectiveness. In pavement condition the following performance indicators were physically measured on the study stretches. A set of examples and results for different overlay methods is also supplied to. An easy to use continuous beam analysis program for the microsoft windows platform.
Estimation for the widening and overlay can be computed. Benkelman beam, dynaflect, falling weight deflectometer fwd and etc. Design of overlay irc design curves relating characteristic pavement deflection to the cumulative number of standard axles are to be used. It can be used in bbd studies for the estimation of characteristic deflection calculations based on irc81, 1997.
Both the fwd and instrumented benkelman beam are used in new zealand to measure the deflection bowl. Determination of the thickness and the type of overlay. Using falling weight deflectometer data with mechanistic. The application of elastic theory to the design of overlays on existing pavement requires that the modulus of elasticity be assigned to the existing structural system. Jul 12, 2017 for this type of roads, a light weight deflectometer lwd may be useful for structural evaluating the pavement layer moduli and overlay design. Functional evaluation is by pavement condition survey, roughness survey and skid resistance measurements. By suitably placing the probe between the dual wheels of a loaded truck, it is possible to measure the rebound and residual deflections of the pavement structure. Structural evaluation of flexible pavement by benkelman beam and falling weight deflectometer pavement condition rating homogeneous sections overlay design, strengthening and rehabilitation of flexible pavement 11. Lecture series on introduction to transportation engineering by prof. Horizontalreading, digital gauge for use with the benkelman beam. Pavement deflection is measured by the benkelman beam which consists of a slender beam 3. Bbd stands for benkelman beam deflection highway engineering suggest new definition. This method is done to lay down a uniform procedure for the design of flexible overlays or per i r c. Structural evaluation is done by benkelman beam deflection method.
Elastic moduli are determent from pavement surface deflection. Comparative studies between benkelman beam deflections. The deflection of the pavement after the corrections i. Rebound deflection is defined as the amount of vertical rebound deflection of a pavement surface due to the moving load bina marga, 2005. Ai deflection method, requires several parameters such as benkelman beam deflection measurements and projected overlay traffic to determine the design overlay thickness using available design charts ai 1996. This was obviously the first deflection parameter which came with the benkelman beam. Recommendations 59 reference 60 appendix source code of the software 63 vi. Structural overlay design of flexible pavement by nondestructive test methods in louisiana by zhong wu1, ph.
The benkelman beam survey is carried out at every 50 meter interval. Specifications for measurement condition survey and deflection data are used. Strength evaluation of flexible pavement of runway using. Introduction ndt benkelman beam deflection measurement calculation correction overlay static deflection measurement the point on the pavement to be tested is selected and marked.
Differences the calculation caused of parameters the data used. The ai deflectionbased approach also requires an additional critical season. It has been used for many years as the primary input for several overlay design procedures. Analysis of this data are shows in next chapter and other benkelman beam survey data shows in figure 3. Comparative analysis of pavement rehabilitation designs.
Comparative analysis of pavement rehabilitation designs using. This pavement analysis tool provides the following features. Marshall method of mix design design criteria aggregate properties design procedure for design of dbm, bc and sma. Collection and interpretation of pavement structural. E design of overlays from deflection data and preparation of structural. The data acquisition calibration factor of a benkelman beam is determined by applying known deflections to the beam tip and comparing each calibration jig dial gauge reading to the deflection calculated by the deflection test computer program bwl4.
This has led to calls for developing a reference method to validate a measurement outcome and confirm true overlay accuracy. Sudhakar reddy, department of civil engineering, iit kharagpur. Additionally, the seasonal model was used to design a 20year ac overlay in arcadia, new york. Deflection based nondestructive pavement analyses pavement. The benkelman beam deflection method is thus widely used for evaluation of structural capacity of existing flexible pavements and also for estimation and design of overlays for strengthening of any weak pavement for highways. This paper focuses on evaluating the structural capacity of pavements. Pavement evaluation by benkelman beam of state highway. The development of an analytical overlay design procedure.
Pdf mechanistic design of overlay based on benkelman beam. History of benkelman beam deflection technique2 development of methods such as benkelman beam deflection method for evaluation of structural capacity of existing flexible pavements and also for estimation and design of overlays for strengthening of any. Mechanistic design of overlay based on benkelman beam. Bearing plate and benkelman beam apparatus, asfaltomezcla. Adjustable feet for benkelman beam, complete with two spirit level calibration device 80b01803 calibration device for 80b0180 benkelman beam apparatus. When backanalysing the deflection bowls, the user informs the program of. Use of an automated temperature data logger atdl during. The design results obtained from both the methods are compared. Thickness design on flexible pavement aashto 1993 method. To verify the correct performance of the apparatus.
Tutorial session on analysis and design of flexible pavement. This analysis will provide a better understanding of differences in overlay thicknesses using different methods of pavement rehabilitation design. Benkelman beam evaluation of structural capacity of existing pavement estimation and design of over lay for strengthening of weak pavement 5. This program can handle multiple span, and point, uniform, varying uniform and applied moments in the positive and negative direction. In this study attempt has been made to conduct this test on the top of conventional whitetopping. The primary device used in the static loading method is the benkelman beam. For this type of roads, a light weight deflectometer lwd may be useful for structural evaluating the pavement layer moduli and overlay design. Other configurations are cantilever left, right side or both sides and it also has a hinge option. Standard test procedure for benkelman beam deflection. Where the colors are stacked directly over each other, they blend to create a darker color, making it easier to see which. Overlay design by benkelman beam road surface standard. Backanalysis of a measured deflection bowl is a widely accepted method for estimating the existing pavement materials elastic properties this is required for undertaking the rehabilitation treatments mechanistic design. Nondestructive deflection testing based mechanisticempirical. One of the methods used in indonesia in thick layer added overlay design on flexible pavement is a rebound deflection method.
In some parts around the globe, still uses conventional benkelman beam deflectometer bbd method for structural evaluation purpose. Steps in design of overlays measurement and estimation of the. Conventionally in india overlay of flexible pavement design is carried out as per irc. General backanalysis of a measured deflection bowl is a widely accepted method for estimating the elastic properties of the existing pavement materials as required for the mechanistic design of rehabilitation treatments.
Flexible road pavement using benkelman beam deflection bbd technique. The new zealand transport agency nzta decided it should revisit the design of electronic instrumentation that could be attached to standard benkelman beams to measure surface deflection. These results further guide in the design of the overlay thickness. Beam pro continuous beam analysis program software. The design is checked by software iitpave for horizontal tensile strain computed. For highways, the point should be located 60cm from the pavement edge if the lanewidth is less than 3. Benkelman beam apparatus, asfaltomezcla bituminosa testing. Using the lwdmod software, elastic modulus of the existing pavements is determined and overlay thickness has been designed. Each layer is transparent and blends with the layers below it. Structural capacity can be measured using a benkelman beam, dynaflect or by using a falling weight deflectometer fwd. Comparison study of overlay design for engineering. Figure 3 mounting brackets for benkelman beam f tape measure and pavement marker 1 chalk, paint or some other method of marking the pavement locations.
Benkelman beam test has also been conducted following irc 81 1997on the entire road network to design the overlay. Directreading dial indicator eliminates need for conversion tables or field calculations. It should be used to find out the overlay thickness of the flexible over flexible pavement as per irc81 1997. Overlay design was done and thickness of the overlay was estimated as ranging between 110mm to 210mm in terms of bituminous macadam. Mechanistic evaluation of asphaltic pavement based on. Home asphalt road quality testing benkelman beam benkelman beam for flexible pavement deflection testing. The overlay design examples include different treatments of the existing ac and pcc surfaces. The program also corrects for secondary effects if the beam support points are affected by the deflection bowl. Both the fwd and instrumented benkelman beam can be used to measure the deflection bowl.
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