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. The deflection of the loaded beam can be obtained various methods. Evolution of the deflection according to truck overloading. The beam is placed in contact with the surface under test between the vehicle tyres. New pavement construction in iowa has decreased with a corresponding increase of restoration and rehabilitation. For carrying out any type of maintenance activity, evaluating the flexible. It will serve as a guide to field personnel in conducting the test and determining the estimate of load carrying. Pavement evaluation by benkelman beam of state highway. 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. Strength evaluation of flexible pavement of runway using benkelman beam deflection technique for surat airport project. Strength evaluation of flexible pavement of runway using. Assessment of need for structural overlays using benkelman beam.
Collection and interpretation of pavement structural. Conjugate beam method castiglianos theorem virtual work method. 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. Maintenance activity is prioritized using composite index method. Bernoullis hypothesis about the plane crosssections is valid. Deflection approach the structural strength of pavement is. The deflection of the pavement after the corrections i. Benkelman beam deflection measurements nz transport agency. Deflection should be find out by benkelman beam deflection test. Horizontalreading, digital gauge for use with the benkelman beam. In the case of the beams, we use this term for linear vertical displacement. The requirements of a typical benkelman beam as shown in figure 4 are listed in test methods t160 and t199.
For instance, if the benkelman beam deflection is 0. Beam deflections double integration method example part. We are offering benkelman beam apparatus, which measures the deflection of a flexible pavement under moving wheel loads in accordance with aashto test t256. To simulate the benkelman beam only one of 10 deflection sensors on the fwd is used for the tonn method. Dynamic deflections to determine roadway support ratings. Supplied complete with a wooden transport case 430mm x 1800mm x 350mm.
Ai deflection method the overlaid pavement is considered as a two layer. Pdf comparative studies of lightweight deflectometer and. Manufactured from aluminium alloy and supplied complete with dial gauge and accessories, the benkelman beam is used to measure the road surface deflection when under load from vehicle wheels. Besides the instrument improvement the authors developed a new method for the processing of the deflection basin data.
Method aims determine the slope and deflection by using moment area method expected outcomes. The magnitude of rebound deflection of a flexible pavements when a standard wheel. 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. To lay down a uniform procedure for the design of flexible overlays using the benkelman beam deflection technique tentative guidelines of flexible road pavements using benkelman beam deflection technique irc. A falling weight deflectometer fwd is a testing device used by civil engineers to evaluate the physical properties of pavement. 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. 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. Benkelman beam deflection testing company india, tamilnadu. Deflection beam has been in use in india for more than two decades by different organizations. Deflection is measured when the vehicle passes over the test area. Direct reading dial indicator eliminates need for conversion tables or field calculations. Measuring the bearing capacity of forest roads with an. Relationship is drawn between deflections readings measured by benkelman beam on x axis and deflections readings obtained by fwd on y axis.
Correlation between deflections measurements on flexible. 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. A benkelman beam is a pavement deflection measuring device which has now been replaced with the fwd. Specifications for measurement condition survey and deflection data are used to establish sections of uniform performance at least 10 deflection measurements should be. This definition appears rarely and is found in the following acronym finder categories. Referenced documents purchase separately the documents listed below are referenced within the subject standard but are not provided as part of the standard aashto standard. Calculate the slope and deflection at the free end. A cantilever beam is 5 m long and has a point load of 50 kn at the free end. Benkelman beam deflection measurements 5 pages, 40 kb. Benkelman beam flexure and surface regularity impact.
Fwd data is primarily used to estimate pavement structural capacity for 1 overlay design and 2 to determine if a pavement is being overloaded. Fkbbb correction factors of benkelman beam bb test load curve models of road deflection. Results are presented through the case study of a 2nd class opening up forest road. The benkelman beam structural test of flexible pavements was replaced in 1976 by dynamic deflection testing with a model 400 road rater. The design traffic in terms of cumulative standard number of axles is to be used. One of the easiest and convenient ways of designing an overlay for strengthening is by using benkelman beam deflection bbd technique which measures the. Able to analyze determinate beam deflection and slope by moment area method. The method also describes the procedure for the calibration of the deflection data acquisition system ddas and bwl4 manual, queensland.
This unit is made from lightweight aluminium and features a telescoping design to reduce weight and storage space. Home asphalt road quality testing benkelman beam benkelman beam for flexible pavement deflection testing. Also given is the method for computing allowable spring axle load from the test data. Pdf mechanistic design of overlay based on benkelman beam. Methods actually calculate the deflections in the pavements. Deflection testing of earthwork and pavement layers roads and. However, at the 95 percent confidence level the bearing value of the section in. 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.
Sep 22, 2015 this test procedure covers the determination of the rebound deflection of a pavement under a standard wheel load and tyre pressure. Mechanistic design of overlay based on benkelman beam deflection technique a case study of rajkotmorbi state highway24. Sep 11, 2015 test method for determination of elastic modulus of pavement structure using benkelman beam, with each country have standard about it vi. Bbd stands for benkelman beam deflection highway engineering suggest new definition. The road rater is used to determine structural ratings of flexible pavements. Published reports omitted important considerations which could influence measurement by the benkelman beam of deflection and curvature of flexible pavements under load.
The probe beam, supported by a rigid reference beam, measures deflections using its 2. History of benkelman beam deflection technique1 devised by a. Shabana thabassum 5 correlates the deflection and unevenness index ui for evaluation of flexible pavements. It should be used to find out the overlay thickness of the flexible over flexible pavement as per irc81 1997. Development correlation between benkelman beam deflection and. 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. The benkelman beam measures the deflection of a flexible pavement under moving wheel loads. Towards a mechanistic analysis of benkelman beam deflection. It is widely used all over the world evaluation of the requirements of strengthening of flexible pavements. Tonn program minnesota department of transportation. Deflection of beams introduction a deflection is the displacement of structural element under load. The magnitude of rebound deflection of a flexible pavements when a standard wheel load of truck is moved forward is measured.
The results showed that the values read on the beam in the case of the load of. Its used to measure the structural capacity of a flexible pavement. Measured deflections collected with the fwd are adjusted for load, temperature, and season tables dddddd, and a benkelman beam correction. The one of the method for finding the deflection of the beam is the direct integration method, i. Diagram showing critical dimensions of benkelman beam 2. 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. Pavement deflection is measured by the benkelman beam which consists of a slender beam 3. Overlay design by benkelman beam road surface standard. The benkelman beam is the simplest and the oldest deflection test device, developed in the united states in the mid1950s. And strengthening is the most adopted method as a pavement maintenance measure. Comparative studies between benkelman beam deflections. Deflectometer rdd, benkelman beam deflectometer bbd. Pdf the paper introduces a new method for calculating the elastic moduli of pavement layers.
Benkelman devised the simple deflection beam in 1953 for measurement of pavement surface deflection. Benkelman beam deflection bbd test benkelman beam is less expansive deflection measuring equipment and method of study is simple and easy to carry out. Measures the deflection of a flexible pavement under moving wheel loads. It was decided that 8 sets of observations of the benkelman beam deflection test may be taken. Benkelman beam deflection testing company india, roads and highway testing services, deflection testing company india, highway consultants. The goal of the research is to come to a mechanistically based analysis procedure of the benkelman beam deflection test results, useful in especially developing. Dynamic deflections to determine roadway support ratings, hr. Comparative studies between benkelman beam deflections bbd. Electronic upgrade of a standard benkelman beam to enable. The hm574 benkelman beam is a simple leverarm device which measures deflection of flexible pavements under the action of moving wheel loads. Pdf effect of pavement stiffness on the shape of deflection. Velciti done benkelman beam deflection for various state and cities roads and highways.
Standard guide for general pavement deflection measurements. Deflection of beam theory at a glance for ies, gate, psu 5. 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. Pddx pavement deflection data exchangetechnical data guide, version 1. Benkelman beam for flexible pavement deflection testing. Deflected pavement structure bounce back to original shape deflected surface original position l o a d l o a d load removed 10. 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. Benkelman beamauxiliary instrument of the maintenance engineer. Hibbeler, 7th edition, prentice hall structural analysis, hibbeler, 7th edition, prentice hall. Rebound deflection is defined as the amount of vertical rebound deflection of a pavement surface due to the moving load bina marga, 2005. Deflection dx 4step procedure to solve deflection of beam problems by double integration method. This test procedure covers the determination of the rebound deflection of a pavement under a standard wheel load and tyre pressure. 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. Comparative studies of lightweight deflectometer and benkelman beam deflectometer in low volume roads article pdf available in journal of traffic and transportation engineering 35.
Jun 26, 2016 the benkelman beam is the simplest and the oldest deflection test device, developed in the united states in the mid1950s. The product has been added to your basket this product has the following accessories. 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. The most widely used method in india has been benkelman beam deflection bbd method. Benkelman beam consist of slender beam of length 3. Sep 25, 2016 comparative studies of lightweight deflectometer and benkelman beam deflectometer in low volume roads. You can see our benkelman beam deflection testing works below. 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. Both the fwd and instrumented benkelman beam are used in new zealand to measure the deflection bowl.
The method also describes the procedure for the calibration of the benkelman beam. Diagram showing critical dimensions of benkelman beam. 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. This has been attempted several times in the past but resulting devices were often complex and expensive. In the technical bending theory, we make two main assumptions that. It is a convenient and practical device for measuring deflection of flexible pavements under the action of wheel loads. T256standard method of test for pavement deflection measurements. A cantilever beam is 6 m long and has a point load of 20 kn at the free end. This paper describes methods of measuring deflection using the benkelman beam, analyzes the disadvantages of the methods used on the washo road test. Thus the paper discusses about the linear, exponential and logarithmic relationship between benkelman beam deflection and falling weight deflectometer for the edge and. Benkelman beam deflection technique od4p6wzdowlp idocpub.
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