Electronic Upgrade of a Standard Benkelman Beam to Enable Capture of Full Bowl Deflections

Abstract

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. This has been attempted several times in the past but resulting devices were often complex and expensive. A low cost solution would encourage uptake by pavement construction companies that have easy access to the Benkelman Beam apparatus. Information gathered from the Benkelman Beam has been restricted to a few data points that must be read by an operator from a dial gauge and recorded manually. This requires some degree of skill and is prone to subjectivity. By upgrading existing Benkelman Beams with electronic measurement sensors and data recording equipment then full deflection bowl data could be acquired with improved reliability when compared to manual methods of recording. The Benkelman Beam test requires two measurements to be taken, pavement deflection and distance from the loading vehicle. A suitable deflection sensor was chosen. The criteria for choosing a distance sensor was that there would be no mechanical connection to the loading vehicle. A laser sensor was found with a suitable range and resolution. A low cost data acquisition module with software was successfully developed. The completed kit can be built for under $2000USD in parts. This is a fraction of the cost of purpose built electronic beams. The whole test can be completed by one operator.