The probe beam, supported by a rigid reference beam, measures deflections using its 2. Pdf mechanistic design of overlay based on benkelman beam. Benkelman beam apparatus, asphaltbituminous mixture. The deflection of the pavement after the corrections i. Benkelman beam deflection bbd method, lacroix deflectograph, dynaflect, falling weight deflectometer fwd. Pdf the paper introduces a new method for calculating the elastic moduli of pavement layers. 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. The turning deflection rebounds deflection has been the large deflection vertical synchronization the impact on the point of observation, deflection travelers commonly used to design the pavement thickness. The design traffic in terms of cumulative standard number of axles is to be used. However, at the 95 percent confidence level the bearing value of the section in.
Benkelman beam, design, fwd, falling weight deflectometer, nondestructive testing, pavements, pavement deflection, pavement design, rehabilitation design, roads, testing. These methods actually calculate the deflections in the pavements. Hibbeler, 7th edition, prentice hall structural analysis, hibbeler, 7th edition, prentice hall. The procedure calculation deflection method using the bb benkelman beam is. Benkelman beam instrument was used to measure the deflection. A simple instrument was developed by modifying the benkelman beam so that the ordinates of the rebound deflection bowl could be measured at five points at 75mm intervals from the center of dual wheel load, using four additional sets of auxiliary levers and dial gauges. How is benkelman beam deflection highway engineering abbreviated.
One of the easiest and convenient ways of designing an overlay for strengthening is by using benkelman beam deflection bbd technique which measures the rebound deflection of the pavements. Irc manual for construction and supervision of bituminous work, new delhi. The method also describes the procedure for the calibration of the benkelman beam. The probe is 2440 mm long and the back extension is 1220 mm. Introduction the benkelman beam instrument is used to measure the deflection of the road. It was decided that 8 sets of observations of the benkelman beam deflection test may be taken. Of all the methods by which to analyze dynaflect deflection data the vaswani method 1 offers the most graphic representation of. 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. There are various methods by which the overlay required can be calculated. 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. Diagram showing critical dimensions of benkelman beam 2.
The benkelman beam is the simplest and the oldest deflection. Towards a mechanistic analysis of benkelman beam deflection. An important drawback when using the device is that most analysis methods of the. Guidelines for deflection testing, analysis, and interpretation fhwa. This paper introduces and describes the benkelman beam deflection test. That sort of reasoning may lead to the conclusion that a new. Pavement testing, analysis and interpretation of test data 2000.
Thus the paper discusses about the linear, exponential and logarithmic relationship between benkelman beam deflection and falling weight deflectometer for the edge and. Standard guide for general pavement deflection measurements. Using fwd data with me design and analysis, volume i. Benkelman beam test scope this method describes the procedure for the determination of rebound deflection and curvature function of a flexible pavement under a standard wheel load, using the benkelman beam. In the case of the beams, we use this term for linear vertical displacement. A truck with a single rear axle and dual back wheels. Jun 26, 2016 the benkelman beam is the simplest and the oldest deflection test device, developed in the united states in the mid1950s. Several organisations have adopted the benkelman beam deflection method for structural evaluation of flexible pavements and overlay design the aashto, the asphalt institute, the transport and road research laboratory trrl, london, the canadian good roads association cgra, besides the indian roads congress irc to name a few. Correction problem of pavement evaluation with fwd deflection. 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. Method aims determine the slope and deflection by using moment area method expected outcomes. For instance, if the benkelman beam deflection is 0.
Specifications for measurement condition survey and deflection data are used to establish sections of uniform performance at least 10 deflection measurements should be. Benkelman beam deflection measurements nz transport agency. Besides the instrument improvement the authors developed a new method for the processing of the deflection basin data. The results showed that the values read on the beam in the case of the load of. Deflection data acquisition system ddas and bwl4 manual, queensland.
Bbd is defined as benkelman beam deflection highway engineering rarely. Benkelman beam include its inability to measure a deflection basin and only. Bb tool is based on the principle of the use of a simple measuring rod and use the dial guages to measure the surface deflection under the influence of load on the pavement. Benkelman beam is less expensive deflection measuring equipment and the method of study is simple and easy to carry out. The analysis of deflection data collected by the falling weight deflectometer fwd. The magnitude of pavement deflection is an indicator of the pavements ability to withstand traffic loading. Measuring the bearing capacity of forest roads with an. Experimental setup of benkelman beam deflection equipment the arrangement was made for benkelman beam deflection test on runway for evaluation of structural capacity of existing flexible pavement. Some engineers have reasoned that the understanding of pavements and their behavior is applicable only if the benkelman beam or some similar device is used. A cantilever beam is 5 m long and has a point load of 50 kn at the free end. The benkelman beam is the simplest and the oldest deflection test device, developed in the united states in the mid1950s.
The benkelman beam is used with a loaded truck typically 80 kn 18,000 lb on a single axle with dual tires inflated to 480 to 550 kpa 70 to 80 psi. We will also give an overview, from the literature and from our own experience, of the ways in which the measurements are presented and interpreted. The benkelman beam measures the deflection of a flexible pavement under moving wheel loads. Pdf evolution of the deflection according to truck. One of the easiest and convenient ways of designing an overlay for strengthening is by using benkelman beam deflection bbd technique which measures the rebound deflection. The benkelman beam is an instrument that is normally used in conjunction with a rolling wheel load. The permissible maximum allowable benkelman beam deflection for satisfactory performance of a road stretch depends upon the traffic, material of construction, and the environmental factors. This test procedure covers the determination of the rebound deflection of a pavement under a standard wheel load and tyre pressure, with or without temperature measurements. The apparatus is used to measure the deflection of flexible pavements under the axion of moving wheel loads. Pavement evaluation by benkelman beam of state highway.
Measurement is made by placing the tip of the beam between the dual tires and measuring the pavement surface rebound as the truck is moved away see figure 17. Operating on a simple lever arm principal, the device consists of a reference beam body, twopart probe beam, and rear zero adjustment assembly. Its used to measure the structural capacity of a flexible pavement. Evolution of the deflection according to truck overloading. Benkelman beam for flexible pavement deflection testing. Ai deflection method the overlaid pavement is considered as a two layer. Deflection method date page 2001 03 15 1 of 2 infrastructure introduction this section presents the overlay design procedure based on the analysis of benkelman beam rebound deflection testing. Benkelman beam deflection bbd test benkelman beam is less expansive deflection measuring equipment and method of study is simple and easy to carry out. For the love of physics walter lewin may 16, 2011 duration. It consists of a lower beam 12 ft long that pivots at 1 california. 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. Test method tnz t1 1977 benkelman beam test dear cetanz member, please find attached the results from the benkelman proficiency testing organised by cetanz in may 2008. Measures the deflection of a flexible pavement under moving wheel loads.
Horizontalreading, digital gauge for use with the benkelman beam. You can see our benkelman beam deflection testing works below. The benkelman beam operates on a simple lever arm principle. Deflected pavement structure bounce back to original shape deflected surface original position l o a d l o a d load removed 10. Pdf analysis of engineering characteristics of pavement. Definition of method of determining beam deflections. It should be used to find out the overlay thickness of the flexible over flexible pavement as per irc81 1997. Bernoullis hypothesis about the plane crosssections is valid. The existing theory analysis and research achievements indicate that they have good.
The deflection is measured as the vehicle passes over the test area. The hm574 benkelman beam is a simple leverarm device which measures deflection of flexible pavements under the action of moving wheel loads. Comparison of falling weight deflectometer with other. Deflection should be find out by benkelman beam deflection test. Benkelman devised the simple deflection beam in 1953 for measurement of pavement surface deflection. Relationship is drawn between deflections readings measured by benkelman beam on x axis and deflections readings obtained by fwd on y axis. Based on present study, graphical method which deflection dependent was developed to determine parameters of elasticity. Comparison study of overlay design for engineering. Both the fwd and instrumented benkelman beam are used in new zealand to measure the deflection bowl. Calculate the ratio l of the deflection at the free end to the length, assuming that the beam carries the maximum allowable load. Deflectometer rdd, benkelman beam deflectometer bbd.
In this method, the deflection of the beam at any point is made equal to the resultant of deflections at that specific point created by the every load acting on the beam individually. In the technical bending theory, we make two main assumptions that. History of benkelman beam deflection technique1 devised by a. Nine laboratories took part in the benkelman beam proficiency test. Results of deflection measurement by benkelman beam method and determination of the characteristic deflection. Benkelman beam consist of slender beam of length 3. Development correlation between benkelman beam deflection and.
Sep 22, 2015 this test procedure covers the determination of the rebound deflection of a pavement under a standard wheel load and tyre pressure. Comparison of testing methods the benkelman beam was developed at the washo road test for the purpose of measur ing the deflection of a flexible pavement under a loaded pneumatic tire. The magnitude of rebound deflection of a flexible pavements when a standard wheel. Paper open access related content road maintenance. 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. This includes simple criteria on maximal deflection dm, the exploitation of the radius of curvature. Figure 7 shows suitable rib and block tyres and unsuitable riblug and lug type tyres. The results of the deflection measurements from the fatickkaolack road with modulation of the axle load of 10, and 16 tons are given in table 1 the results showed that the values read on the beam in the case of the load of 10. Able to analyze determinate beam deflection and slope by moment area method.
Ensure that the displacement measuring device is set within an appropriate range. The vertical deflection is recorded by a special measuring beam, which is mounted on a support frame that can be rotated at a ratio of 1. With the benkelman beam measurement method, the vertical deflection of the road surface is measured after a defined load of 5 tons has rolled away. Assessment of need for structural overlays using benkelman beam. 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. Benkelman beam deflection testing company india, tamilnadu. Elastic moduli are determent from pavement surface deflection. Benkelman beam conducted under washo method to collect data in order to find deflection condition of existing pavement.
Pdf on jan 1, 2018, fatou samb and others published evolution of the deflection according to truck overloadingcomparison between benkelman beam method and fem of lateritic pavements find. Conversion of fwd deflection to benkelman beam deflection. A simple method of measuring pavement rebound deflection. Overlay design by benkelman beam road surface standard. Benkelman deflection more than the allowable deflection suggests that the pavement may require an overlay. In operation the beam is placed between the tyres of the test vehicle and in contact with the pavement. The most widely used method in india has been benkelman beam deflection bbd method. Comparative studies between benkelman beam deflections bbd. Ijsrd international journal for scientific research.
Benklemam beam is one of the most commonly used methods for measuring deflection of the pavement surface. This has been attempted several times in the past but resulting devices were often complex and expensive. Whenever new pavement is to be laid this reading is helpful. Benkelman beam deflection measurements 5 pages, 40 kb. The method also describes the procedure for the calibration of the deflection data acquisition system ddas and bwl4 manual, queensland. Deflectometer were used to load the pavement, while the benkelman beam was used to measure the induced deflection. The deflection of the loaded beam can be obtained various methods. The beam fulfilled a need for a simple instrument that could quickly and conveniently measure the pavement sur face deflection at any point. Test method t160 deflection measurement portable beam 2 of 4. Calculate the slope and deflection at the free end. The indian roads congress 9irc has issued guidelines for conducting benkelman beam deflection bbd studies for structural evaluation of flexible pavements and for the design of overlay thickness for strengthening the.
Benkelman beam deflection testing was done to measure the characteristic deflection of the pavement surface and fifth wheel bump integrator was used to calculate the roughness index to assess the performance of the pavement. Standard test procedure for benkelman beam deflection. Pdf this paper describes analysis of pavement deflection data collected by the transport. The h3220a benkelman beam apparatus is a convenient and accurate device used for measuring the deflection of flexible pavements under moving wheel loads. Pdf pavement rehabilitation design based on maximum surface. According indonesian highways conditions 2005, the value of rebound deflection that measured by benkelman beam bb devices should be corrected by a factor of ground water table seasonal factors and. Home asphalt road quality testing benkelman beam benkelman beam for flexible pavement deflection testing. Bbd stands for benkelman beam deflection highway engineering. Mechanistic design of overlay based on benkelman beam deflection technique a case study of rajkotmorbi state highway24.
Electronic upgrade of a standard benkelman beam to enable. Using fwd data with me design and analysis, volume iii. Collection and interpretation of pavement structural. The method also describes the procedure for the calibration of the benkelman beam and the rotopulse transducer which determines the spacing at which the data is logged. Velciti done benkelman beam deflection for various state and cities roads and highways. It is widely used all over the world evaluation of the requirements of strengthening of flexible pavements. Measurements of benkelman beam deflections together with records of traffic loading were taken at. A cantilever beam is 6 m long and has a point load of 20 kn at the free end.
Foreword this report documents a study conducted to investigate the use of the falling weight deflectometer fwd as part of mechanisticempirical pavement design and rehabilitation. A benkelman beam that meets the minimum requirements of t160. Materials division texas transportation institute texas a. The magnitude of rebound deflection of a flexible pavements when a standard wheel load of truck is moved forward is measured. Results are presented through the case study of a 2nd class opening up forest road. Deflection approach the structural strength of pavement is. Strength evaluation of flexible pavement of runway using.
The popular methods used under non destructive pavement analysis are falling weight deflection method and benkelman beam deflection method bbd. And strengthening is the most adopted method as a pavement maintenance measure. Direct reading dial indicator eliminates need for conversion tables or field calculations. Benkelman beam deflection technique, evaluate pavement roughness and distress by. The superposition method is one of the best techniques for finding the deflection of the beam. Results of deflection measurement by benkelman beam method and determination of the characteristic deflection the results of the deflection measurements from the fatickkaolack road with modulation of the axle load of 10, and 16 tons are given in table 1.
Deflection of beams introduction a deflection is the displacement of structural element under load. T160 details the type of tyre and the allowable tyre pressure and does not allow the use of lugged type tyres. The extensive use of the modified benkelman beam, the road surface deflectometer coupled with the use of the in depth deflection measurements with the multidepth. Mechanisticempirical pavement design guidea manual of practice. Deflection dx 4step procedure to solve deflection of beam problems by double integration method.
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