Benkelman Beam for Flexible Pavement Deflection Testing

Benkelman Beam for Flexible Pavement Deflection Testing

The Benkelman Beam is a straightforward, portable lever-arm device used to measure the deflection of flexible pavements, such as asphalt, under the stress of moving wheel loads. This measurement is crucial for evaluating the structural integrity and load-bearing capacity of a road surface over time.

How It Works: The apparatus operates on a simple fulcrum principle. A slender probe beam, measuring 2.44m (8ft), is carefully positioned between the dual tires of a loaded test truck. As the truck moves slowly over the test area, the pavement deflects under the weight. This vertical movement is detected by the tip of the probe beam. The movement is then transferred to a dial indicator located at the opposite end of the beam. The pivot point (fulcrum) is positioned to create a 2:1 lever ratio, meaning the deflection reading on the dial indicator must be doubled to determine the actual pavement deflection.

Key Features:

• Simple and Reliable: Its mechanical design makes it a trusted and easy-to-use tool for field testing, providing direct, real-time measurements without the need for complex electronics or power sources (except for the alert buzzer).
• Lightweight and Portable: Constructed from three pieces of anodized, lightweight aluminum, the entire beam weighs only 15kg (33lb). The longest section is just 1.99m (6.5ft), making it easy to transport and assemble on site.
• Precision and Stability: A rigid reference beam provides a stable frame of reference, ensuring that only the pavement's deflection is measured. It includes a leveling adjustment to zero the dial indicator before each test.
• Enhanced Operation: An optional, battery-operated vibrator is included. This buzzer alerts personnel when a measurement is in progress and helps ensure all moving parts are free from friction, improving the accuracy of the reading.

Compliance and Ordering: The Benkelman Beam is designed to meet the standardized procedures outlined in the following test methods:

• AASHTO T256
• ASTM D4695

Please note: A Mechanical Dial Indicator or Digital Dial Indicator is required for operation and must be ordered separately.