Tru-Tension Structural Fasteners
Tru-Tension® Structural Fasteners are a fastening system offering many advantages over conventional structural bolt systems. Lower costs for bolting installation and inspection can add up to tremendous savings when compared to conventional structural bolting systems. In addition to the features offered by the Tru-Tension® Fastening System, you get the added confidence knowing that Tru-Tension® Assemblies come from Nucor Fastener, the leading manufacturer of structural fasteners in the United States. When buying structural products from Nucor Fastener, you are selling fasteners that are formed domestically in our ISO9001 registered facility; from steel melted and rolled in the U.S.A.; and tested in our A2LA Accredited in-house laboratory. Certifications are always available to the purchaser, including original steel certifications. Tru-Tension® Structural Assemblies are installed with a quiet, light weight electric installation tool which reduces operator fatigue and eliminates problems in compliance with OSHA Noise Regulations encountered when using pneumatic impact wrenches. Since the bolt is calibrated so the spline tip twists-off when the proper bolt tension is achieved, there is no need to rely on a calibrated wrench or on an operator’s skill to correctly install the bolt to the proper tension. Tru-Tension® Assemblies feature a specially developed lubricant system which provides consistent assembly properties over a wide range of installation conditions. The correct fastener tension in compliance with AISC Bolting Specifications is achieved in the Tru-Tension® Assembly, because the bolt assembly is factory calibrated. Evidence of proper tension can be accomplished by visual inspection to see that the spline has twisted off, thus reducing the expense of more costly bolting inspections.
Dome Head Tru-Tension® Fasteners From Nucor Fastener
Tru-Tension® Assemblies are manufactured to ASTM F1852 (A325 equivalent) or ASTM F2280 (A490 equivalent) standards in the United States using domestically produced steel. Each Tru-Tension® Bolt is pre-assembled with an ASTM F436 Hardened Washer and a Heavy Hex Nut. The lots are fully traceable from raw material through to finished product. Each lot is fully tested by our A2LA Accredited Laboratory and certified test reports are included with each shipment. The bolts are supplied as ASTM F1852 (“Standard Specification for “Twist Off” Type Tension Control Structural Bolt/Nut/Washer Assemblies, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength”) or ASTM F2280 (“Standard Specification for “Twist Off” Type Tension Control Structural Bolt/Nut/Washer Assemblies, Steel, Heat Treated, 150 ksi Minimum Tensile Strength”) with a dome (round head) or heavy hex head configuration. The mechanical properties, threads, and thread length are the same as for Heavy Hex Structural Bolts. The diagram and table (below) show the dimensions of the dome head configuration used by Nucor Fastener. The heavy hex head configuration can be supplied by special order. The correct fastener tension, in compliance with AISC/RCSC Bolting Specifications (covered in the “Specification for Structural Joints Using ASTM A325 or A490 Bolts”), is assured by proper control of the dimensions (especially the groove diameter of the spline) and friction conditions.
Advantages And Features Of Tru-Tension® Fasteners From Nucor
Meets or Exceeds AISC Tension Requirements
• Provides dependability by consistently exceeding the minimum AISC bolt installed tensions.
• Fully tested and certified assemblies.
• Installation is completed without putting torsion into bolt length – only the bolt length between the nut and splined tip is in torsion – the balance of the bolt is in tension, providing more consistent and greater available bolt tensions.
Buy with Confidence
• All Products 100% Made in USA.
• Large Inventory.
• Capable of Producing a Full Range of Product Diameters and Lengths.
• World Class Customer Service and Technical Support.
• Full Traceability, just like all other Nucor Fastener Products.
Easy to Install
• Can be used anywhere a standard structural bolt is used (provided that it is acceptable to the responsible designer or project engineer).
• Does not depend on tool calibration or operator skill for proper assembly.
• Lightweight installation tool.
– Electric tools are powered by 115 or 220 volts.
– Quiet installation system.
• Reduced operator fatigue.
– Non-Impacting Electric Tool.
– No external reaction moment (to twisting).
– Easier to setup and move than air compressor and air lines.
• Shipped assembled (nut, bolt & washer) in sealed metal kegs. No field nutting required.
• Pre-assembled fasteners that ensure matched sets – saves assembly time.
Allows For Rapid Visual Inspection
• Eliminates operator error during assembly.
• Can visually inspect for proper installation by seeing that the spline has twisted off.
• No need for expensive installation tool calibration.
Reduced Cost of Installation
• Save money in installation.
– Increased installation speed (typically 2 to 3 times more bolts installed per man-hour).
– Lower inspection costs (quick visual check vs. typical rechecking of – 5% of all joints).
• Pre-assembled fasteners that ensure matched sets – saves assembly time.
• One man, one side assembly (no need for a back-up man).
• Tru-Tension® Bolting can save money in shop fabrication by using bolted web stiffeners and gussets rather than welding. Successful bolt installation does not require highly skilled labor.
Typical Expected Cost Savings
The following information is an overview of typical savings that may be possible when using Tru-Tension® Fasteners instead of a standard A325 Bolt with a nut and washer.
The cost of the first three rows will vary by project. The cost of additional paperwork and maintenance of the individual containers can be expected to take up to ½ hour per lot of received material. Pre-testing is very quick and simple for Tru-Tension® products. If calibrated torque wrenches are used for installation, pre-testing must be done on a daily basis (resulting in several additional hours over the course of the project). Also, tool calibration is required for installation by torque.
Handling, Storage And Pre-Installation
Handling and Storage
The following information, from the AISC/RCSC “Specification for Structural Joints Using ASTM A325 or A490 Bolts”, is applicable to all high strength fasteners, including Tru-Tension® products: “Fasteners shall be protected from dirt and moisture at the job site. Only as many fasteners as are anticipated to be installed and tightened during a work shift shall be taken from protected storage. Fasteners not used shall be returned to protected storage at the end of the shift. Fasteners shall not be cleaned of lubricant that is present in as-delivered condition.” The last point is very important for Tru-Tension® Fasteners. The lubrication condition on the fasteners cannot be modified, that is, never clean, strip or add additional lubrication to the product. Opened cans should be stored indoors, protected from the elements, to prevent environmental contamination from rain, dirt, rust, etc...
Use of Washers
The ASTM F436 Washer included with the tension control assembly must be placed under the nut in all cases. Refer to section 6 of the RCSC “Specification for Structural Joints Using ASTM A325 or A490 Bolts” for additional requirements governing the use of additional washers.
All of the fasteners in the connection must be brought to a snug tight condition prior to final tightening. This method will prevent interactions between bolts as additional bolts are tightened. As always, fasteners should be tightened in sequence from the most rigid section outward. In some cases, this may require more than a single cycle of systematic tightening or tightening in a pattern.
Representative samples should be checked at the job site in a device capable of indicating bolt tension. The testing should demonstrate that the system develops the proper tension, prior to installation, in accordance with RCSC recommendations.