BENKELMAN BEAM METHOD
A.C.Benkelman devised the simple deflection beam in 1953 for measurement of pavement surface deflection. It is widely used all over the world evaluation of the requirements of strengthening of flexible pavements. This method is done to lay down a uniform procedure for the design of flexible overlays or per I R C:81-1981 here a tentative guideline was published by the Indian road congress under the title “Tentative Guidelines for strengthening of flexible road pavements using Benkelman beam Deflection technique” . THEORY: Due to traffic or repetition of load wearing course of the pavement surface gets deteriorated. So to overcome this problem performance analysis of the pavements surface is done. Performance of flexible pavements is closely related to the elastic deformation of pavement under the wheel loads. The deformation or elastic deflection of pavement under a given load depends upon sub grade soil type, its moisture content and compaction, the thickness and quality of the pavement course, drainage conditions pavement surface temperature etc. Pavement deflection is measured by the Benkelman Beam which consist of slender beam 3.66m long pivoted at a distance of 2.44m probe point. 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 stricture. Rebound deflection is used for overlay design. * Rebound Deflection: The deflection within elastic limit, i.e, recoverable deflection or elastic deflection. In a well designed road, deflection is entirely elastic and recoverable. * Residual Deflection: Non recoverable deflection. As a pavement get aged, it loses a portion of its elastic properties and a permanent deflection takes place. CRITERIA FOR CLASSIFICATION OF PAVEMENT SECTIONS:
| Pavement Condition
| No cracking, rutting less than 10mm.
| No cracking or cracking continued to single crack in the wheel...
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