What type of tension indicators does the standard ASTM F959 refer to?

The standard ASTM F959 refers specifically to compressible washer-type direct tension indicators. These devices are designed to provide a visual indication or measurement of the tension in a bolted joint by using a compressible washer that deforms under load. The key feature of these indicators is their ability to indicate the amount of tension directly, which is crucial for ensuring that bolts are tightened to the correct level necessary to maintain structural integrity.

Compressible washer-type direct tension indicators operate primarily by allowing for precise control over clamping force in bolted connections. As they compress, specific visual markers indicate the degree of tension. This is especially important in applications where the bolted connection must maintain a consistent preload to avoid loosening due to vibration or dynamic loading.

Understanding the significance of using such indicators is essential for professionals involved in structural steel assembly and connections. They help ensure proper installation procedures are followed, contributing to overall safety and reliability in construction practices.