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Federal Highway Administration
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Washington, DC 20590
202-366-4000


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Bridges & Structures

High Strength Bolts

Procedures for Performing Rotational Capacity Test

Appendix A1 - A325 Procedure for Performing Rotational Capacity Test Bolts too Short to Fit Tension Calibrator

Revised February 2005

Only those bolts too short to fit in the tension measuring device shall be tested using this procedure. typically these bolts are less than 4 diameters long.

Equipment Required:
  1. Calibrated torque wrench and spud wrenches.
  2. Spacers with holes 1/16 larger than bolt to be tested or nominal diameter washers.
  3. Steel section with holes 1/16 larger than the bolt diameter. Splice holes in the steel on the project can be used.
Procedure:

A Rotational Capacity Test Consists of 2 Assemblies.

  1. Measure the bolt length, the distance from the end of the bolt to the washer face at the bolt head to shank interface.

  2. Install the bolt in the steel plate with the required spacers or washers so that the bolt-stick out is flush with the nut to a maximum of three threads. This will typically provide three to five threads within the grip, the distance between the bolt head and the inside face of the nut. This same stick-out requirement applies during installation.

  3. Provide an initial tension in the fastener assembly using a spud wrench. The torque should not exceed 20% of the maximum torque allowed in step #5.

  4. Match mark the nut, bolt and plate.

  5. Tension the bolt using a torque wrench to rotate the nut as required in the table below. Prevent the bolt head from rotation. Read the torque at the required rotation with the nut in motion.

    Bolt Length (measured in Step #1)    4 x bolt dia. Or less   Greater than 4 x but no less than 8 x bolt dia. 
    Required Rotation 1/3 1/2

    The measured torque should not exceed the values listed below. Assemblies that exceed the listed torques have failed the test. These torque values are based on an assumed tension of 1.15 x minimum installation tension.

    Bolt Dia. (in.)  1/2   5/8   3/4   7/8   1   1 1/8   1 1/4   1 3/8   1 1/2 
    Torque (ft-lbs)   150 290 500 820 1230 1500 2140 2810 3690
  6. Further tighten the bolt to the rotation listed below. The rotation is measured from the initial marking in step 4. Assemblies that fail prior to this rotation either by stripping or fracture fail the test.

    Bolt Length (from step 1)    4 x bolt dia. or less   Greater than 4 x but no less than 8 x bolt dia. 
    Required Rotation 2/3 1
  7. Loosen and remove the nut. There shall be no signs of thread shear failure, stripping or torsional failure. The nut shall turn, with your fingers, on the bolt to the position it was in during the test. The nut does not need to run the full length of the threads. If you cannot turn the nut with your fingers it is considered thread failure.

Failure:

The following constitute a failure of the rotational capacity test.

  1. Exceeding the maximum allowable torque.
  2. Failure to achieve the required rotation.
  3. Thread failure.

Failure of any one of these items on either assembly constitutes a failure of the rotational capacity test. When a failure occurs, the subject lot of fasteners is rejected. The contractor is given the option to clean and re-lubricate as necessary and then retest the fastener assemblies.

Updated: 09/03/2013
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000