What does a direct tension indicator help measure in the installation of bolts?

A direct tension indicator is a specialized device used in the installation of bolts to measure the tension applied to the bolt itself. It provides an accurate assessment of the bolt's tensioning during the installation process, which is crucial for achieving the desired preload in bolted connections. Proper tensioning is essential to ensure the structural integrity and performance of connections in steel fabrication and construction.

By incorporating a direct tension indicator, the installer can confirm that the bolt has reached the specified tension level as outlined in design specifications. This control helps prevent issues such as joint separation, vibration loosening, and failure due to inadequate preload. Direct tension indicators effectively allow the installer to visually or mechanically ascertain whether the bolt tension is within the required range for optimal performance.

The other answer options do not pertain to the function of a direct tension indicator. It is specifically designed not for measuring the length, weight, or resistance of the bolts but rather focuses solely on quantifying the tension applied during the bolting process.