Dynaflect and road rater

Dynaflect and Road Rater are vibrating load devices developed in the United States in the 1970s. They measure dynamic deflection while they are stationary, using a sinusoidal force. Unlike the Benkelman beam and semi-static devices, they are also capable of measuring the deflection basin since deflection is recorded by velocity transducers (usually five). Both devices comply with ASTM D 4695 (2008) and ASTM D 4602 (2008). 

In the Dynaflect, the sinusoidal load, 455 kg peak to peak, is applied through eccentric masses that counter-rotate at a fixed frequency, through two rubber-coated steel wheels. 

Dynaflect deflection measurements may be converted to Benkelman deflection using the correlation equation given in Section 16.4.1.1 or a similar equation. The main drawback of Dynaflect is that since the applied load is low, it is not really suitable for thick asphalt pavements. 

More details about the Dynaflect can be found in Asphalt Institute MS-17 (3rd Edition), Eagleson et al. (1982) and Pavement Interactive. 

---