Falling Weight Deflectometer (FWD)

Falling Weight Deflectometer (FWD)

The Falling Weight Deflectometer (FWD) is used by pavement engineers to evaluate pavement conditions and performance, to determine if there is a need for pavement reconstruction. The data from the FWD can also be used to optimize pavement design and maintenance strategies.

What is a Falling Weight Deflectometer (FWD)?

The Falling Weight Deflectometer (FWD) is an integral part of the process for structural evaluation of pavements. The FWD is a non-destructive and fast method to evaluate the structural capacity of pavements for research, design, reconstruction of the road, and for pavement management purposes.

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The Dynatest Falling Weight Deflectometer (FWD) applies a dynamic load that simulates the impact of a moving wheel. The pavement response is analyzed with Dynatest’s ELMOD (Evaluation of Layer Moduli and Overlay Design) software to determine the elastic moduli, stresses, and strains of each modeled layer. ELMOD reports the weakest layer of failure, residual life and determines the optimal reconstruction alternatives. The FWD is available as a trailer or a truck-mounted version (the USA only) meeting all FWD standards worldwide.

Key benefits and features

  • Automated and rapid structural pavement testing applicable to pavements all over the world
  • Determines the layer of failure, rather than simply determining the bearing capacity
  • Measurement of thin asphalt layers or similar materials even block pavement
  • QA/QC of newly built pavements
  • Compares a range of reconstruction options, including plane off and recycling rather than just applying overlays
  • The use of the FWD provides accurate, reproducible, and repeatable structural data
  • Automated and real-time monitoring of the load cell, geophones, and data variations ensures high quality of collected data
  • Uses mechanistic-empirical analysis applicable to most of pavement structures
  • The FWD is used worldwide from the hottest and driest deserts to the humid tropics and the cooler polar regions
  • Compliance with ASTM D4694-09 and ASTM D4695-03 and equivalent standards. Passes TRL (UK) and CROW (Netherlands) correlation trials. AASHTO R32-11 calibration protocol compliant

Key Operational Features of the Dynatest FWD

  • A non-destructive test device.
  • One person operational.
  • Total flexibility with 7-15 deflection sensors.
  • Accurate and fast (up to 60 test points/hr with a typical 4 load application sequence).
  • No need for road closure.
  • Wide loading range: (4-120 kN) or (1,500 – 27,000 lbf). Extendable to up to 150 kN (33,700 Ibf)
  • Designed for multi-purpose pavement applications, ranging from unpaved roads to airfields.
  • Excellent repeatability.
  • Ideal for mechanistic/analytical design approaches.
  • 4 segmented loading plates to test uneven or rutted pavement surfaces
  • Air and Pavement Surface Temperature Sensors.
  • Distance Measuring Instrument (DMI).
  • High quality for long lasting functionality.
  • The most tested FWD on the market.

Get a closer look

Electro-hydraulic system

Peak load range approximately 4 to 120kN / 150kN

Meets ASTM D-4694, D-4695 and equivalent standards

Up to 15 seismic deflection sensors

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Available Upgrade Options

  • Folding trailer for ease of shipment
  • Global Positioning System (GPS)
  • Additional deflection sensors (up to 15)
  • Camera system for plate location or photo-logging
  • On board generator for standalone operation
  • Trailer cover (soft or hard versions)
  • Trailer mounted light(s) or strobe(s)
  • Rear and side Sensor Extension Bars
  • Ground Penetrating Radar
  • Thin asphalt measuring conversion kit
  • Rear warning sign
  • Spare parts kit
  • Tool kit.

The use of Falling Weight testing

Data collected from the Dynatest FWD can be used to determine the structural capacity of pavements to analyze the physical properties of the ground. When analyzing the data from the Dynatest FWD with the ELMOD software, it is possible to obtain information about the condition of the road, such as: surface layers, subgrade layer, layer moduli, layer types, thickness, range of moduli, Poisson’s ratio and bearing capacity.

This information can be used to estimate overlay requirements, the remaining life of the pavement, and an effective creation of a Pavement Management Plan.

ELMOD Software - only available for Dynatest Equipment

  • Evaluation of Layer Moduli and Overlay Design
  • Dynatest’s ELMOD software may be used for the analysis and design of flexible, rigid, and composite pavements
  • Allows quick data reduction and analysis of FWD load/deflection measurements
  • Capable of back calculation of the layer moduli, for a typical drop sequence, in less than a second
  • Fast calculation of the seasonally adjusted moduli, residual life of the pavement, and required overlay thickness for a given service life
  • For maintenance and reconstruction (M&R), the LCCA (Life Cycle Cost Analysis) module allows the user to select the optimal M&R solution
    for a pavement section according to cost/benefit ratios
  • To analyze the bearing capacity of airfield pavements, the ELMOD software can calculate both the new ACR/PCR classification and the traditional ACN/PCN values. This dual calculation will be available until November 2024, when the new ACR/PCR system becomes fully applicable under FAA AC150/5335-5D guidelines.

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