JSS-II-09
The Twist-off Bolt, commonly known as a tension control (TC) bolt, is a specialized high-strength structural fastener designed for rapid and reliable installation in steel construction projects. This innovative bolt features a unique splined end that shears off at the precise preload moment during tightening using a tension-control wrench, ensuring accurate and consistent bolt tension without the need for torque wrenches or the turn-of-nut method. This shear-off mechanism provides a visual indication of proper installation, greatly simplifying field inspection and quality assurance procedures.
The TC Bolt represents a significant advancement in structural fastening technology, offering substantial benefits over conventional bolting methods. These bolts dramatically reduce installation time—often cutting it by 50% or more—as a single operator can install dozens of bolts per hour with consistent preload accuracy. TC bolts are available in various grades including ASTM F3125 Grade A325 and A490, covering diameters from 1/2"to 1-1/2"with tensile strengths up to 150 ksi (1034 MPa). The bolts are typically supplied as complete assemblies with a matched heavy hex nut and hardened washer, ensuring all components work together seamlessly under high clamping loads.
As a Seismic bolt assembly, the TC bolt system is specifically engineered for critical structural applications requiring enhanced ductility and energy dissipation capacity. The controlled preload provided by these assemblies ensures that steel connections maintain sufficient clamping force to resist both static loads and dynamic forces, such as those generated by earthquakes, heavy winds, and vibration. The consistent and reliable tension achieved during installation eliminates human error and reduces the risk of joint failure under extreme loading conditions. These assemblies are widely adopted in seismic zones for high-rise buildings, highway bridges, stadiums, wind turbine towers, heavy industrial facilities, and other structures where connection integrity is paramount for public safety and structural performance.
