NASCLA Accredited Commercial General ContractorMetalsHard
A contractor is installing a new pedestrian bridge made of structural steel. Before allowing public access, a comprehensive inspection of all bolted connections is required. Which of the following is an acceptable method for verifying the proper tensioning of high-strength bolts in a friction-type connection, according to AISC specifications?
- AUsing a feeler gauge to measure the gap in Direct Tension Indicators (DTIs) if they were installed.
- BVisually inspecting the paint marks on the bolt, nut, and member to ensure relative movement after tightening.
- CApplying a torque wrench to randomly selected bolts to check for movement.
- DHammering the bolt head to check for a 'ring' sound.
Show answer & explanationAnswer & explanation
Correct answer: A. Using a feeler gauge to measure the gap in Direct Tension Indicators (DTIs) if they were installed.
If Direct Tension Indicators (DTIs) were used during installation, measuring the gap between the DTI and the bolt head or nut with a feeler gauge is a direct and approved method for verifying that the specified bolt tension has been achieved. The gaps close as tension increases, providing a measurable indication.
Why the other options are wrong
- B. Visually inspecting paint marks (match marks) is part of the turn-of-nut installation method but is not a primary verification method for tension itself; it confirms rotation, not direct tension.
- C. Applying a torque wrench to already tensioned bolts to check for movement is not an approved verification method and can lead to over-tightening or damage.
- D. The 'hammer test' or 'ring test' is an unreliable and outdated method for verifying bolt tension and is not permitted by modern codes.
Direct Tension Indicator (DTI) Verification
A method of inspecting high-strength bolted connections by measuring the remaining gap in a DTI washer with a feeler gauge to confirm that the specified bolt tension has been achieved.
- DTIs provide a direct and verifiable measure of bolt tension.
- The gap measurement criteria are specified by the DTI manufacturer and project requirements.
- An approved method by AISC for quality assurance.
Memory trick: Tension Check: DTI Gap, Directly Guarantees.