Description
Short technical description: Notable Features The Falling Weight Deflectometer (FWD) is a trailer mounted device, which measures the vertical deflection of a structure under an impact load. Peak deflections are measured over the range 0 to 2mm to the nearest 0.001mm at the centre of a 300 or 450 mm diameter loading plate and simultaneously at up to six additional radial locations with a normal maximum radius of 2.4m. By means of a falling weight striking a specially designed rubber spring system the equipment generates a half-sine shaped impact load of 25 to 30msec in duration of up to 120kN. This closely approximates to the effect of a moving wheel load applied with the same force. The equipment is usually operated by one person. A typical testing sequence at one measurement location is conducted in around one minute, with the data obtained being stored on computer disk for future analysis. The location of test points is recorded as longitudinal distance from known events. This distance is measured by a sensor on one of the trailer wheels. A camera system is available to aid accurate test positioning. The results from the FWD can be used, together with construction information and layer thickness, to provide detailed information on pavement layer elastic stiffness and to identify week areas in need of maintenance or further investigation. The results can be used by engineers to help design appropriate maintenance treatments. TRL was the first organisation to introduce the FWD to the UK and has over 15 years experience in its use. Benefits This is a non-destructive test, usable in all climatic conditions The measurements are computer controlled thereby reducing the possibility of human error. The operator is not normally required to leave the operating vehicle, therefore reducing risk when testing in difficult environments. The equipment can be dismantled for easy transport to overseas locations. The FWD can be very easily located, for example, testing weak spots or for assessing load transfer across joints or cracks. Potential Uses The FWD can be used to test the structural condition of all types of flexible and rigid highway pavements, airport runways and taxiways, ports, parking areas and other structures. Testing can be undertaken at various stages of the construction of a new pavement from the granular foundation to the final surfacing. Testing of existing pavements as an integral part of a structural investigation. To assess the performance of structural maintenance treatments such as vacuum grouting beneath concrete slabs. Assessment of load transfer and slab support on jointed pavements or across cracks in all types of rigid pavements. Design and assessment of crack and seat rigid pavements. Assessment of trench reinstatements and recycled pavements. Construction date: 2003 Last upgrade: 0
Keywords
FWD, Bearing capacity, Deflections, Impact test device, Concrete, Strength test
Comment
Transfered by script test/facilities at 2010-07-29 08:30:49 / other info: >> name_last_updator: Richard Woodward | validator_name: alain maldonado <<