OSCORP ENGINEERING

Falling Weight Deflectometer (FWD)

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.

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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)