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Falling Weight Deflectometer (FWD) is a system used for performing non-destructive testing on pavements and measure the vertical deflection response of a surface to an impulse load to simulate the weight of a passing wheel load.
FWD’s are commonly used on highways, local roads, car parks and airport runways, for a wide range of applications, such as pavement structural evaluation and design.
FWD Features:
- Double Axle Trailer
- Hydraulic Brakes
- 2-cylinder 18-horsepower gasoline engine with 12 volt alternator permits high-speed and independent operation of the tow vehicle
- DGPS enabled
- 4 drop automated sequence in 30 seconds
- Data capture from 1-35 drops at each location with up to 35 forces
- Load Plate: 300mm
- Geophones Accuracy: 2% +/- 1 micron and Range: 0 to 2032 microns
- Force Measurement (Automatic Load Sensing) Accuracy: 1% +/- 0.07kN, Range 0 to 200 kN, Material: Stainless steel
- Temperature Measurement (Pavement)
- Accuracy: +/- 2% rdg, Range: -18 C to 400°C
- Temperature Measurement (Ambient) Accuracy: +/- 2% rdg Range: -18 C to 400°C
- Automatic Load Sensing, Computer automatically determines drop heights for varying loads up to 99 drops.
- Data Output, Data is outputted into AASHTO recommended file format Pavement Data Deflection Exchange (PDDX) format
- Data Acquisition: 1.25 Msamples/second Up to 32 Differential A/D channels 2 Analog Outputs, 8 Digital I/O +/- 10V Input Range.
Benefits of FWD’s:
- Non‐destructive economical pavement testing.
- Imparts a dynamic load to a pavement structure similar to a moving wheel load.
- Measures deflection of the pavement surface.
- Determine pavement structural capacity and pavement performance and remaining life.
- Load transfer efficiency of joints in concrete and identify voids under concrete slabs.
- Project and network pavement structural evaluation.
As deflection data is increasingly used to accurately define pavement response to loading the need to develop robust back-calculation procedures has become greater. With the speed of computers increasing more mathematically intensive procedures can be used for developing solutions of large data sets. The back-calculation program enables the rapid calculation of layer stiffness modulus using a singular decomposition technique.
Oscorp Engineering uses back calculation programs to estimate the layer moduli with the help of accurate Back calculation program which offers the following:
- Automatically iterates the layer module of an input pavement. configuration that best represents the existing pavement structure.
- Consider stress-dependent module of granular materials and sub-grade.
- Assigned values of Poisson’s ratio and degree of anisotropy are consistent with those adopted in Australia roads GMP overlay design.
- Automatically access raw FWD data files and import FWD data from Excel Spread Sheets.
- Automatically perform back-analyses of deflection data from FWD data files to produce solutions of elastic properties for layers.
- Automatically prepare summary reports (in Excel format).
