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Factotum

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- TL;DR Summary
- I have been reviewing the specifications for Red Head Trubolt wedge anchors. I am confused by what appears to be a contradiction between the specified installation torque, the resulting installation axial tensile force, and the anchors ultimate tension specification. I want to understand what I am misinterpreting.

**[Mentor Note: See post #16 for a corrected/updated version of this post]**

https://www.physicsforums.com/threa...vs-ultimate-tension-spec.1056964/post-6965453

I have been reviewing the specifications for Red Head Trubolt wedge anchors. I am confused by what appears to be a contradiction between the specified installation torque, the resulting installation axial tensile force, and the anchors ultimate tension specification. Per my calculations, the installation torque would result in a tensile force greater than the ultimate tension specification for the anchor. Since the allowable tension specification is 25% of the ultimate tension specification, the installation tensile force would far exceed the allowable tension specification. If my understanding and calculations are correct, there is a good chance that applying the installation torque to the anchor will cause the concrete to fracture.

I figure one of two things is happening. Either, I am incorrectly calculating the installation axial tension force, or I am misinterpreting the ultimate tension specification.

Per my understanding, the ultimate tension specification conveys the force needed to pull the anchor from the concrete. An event that usually results in fracturing and dislodging a cone of concrete along with the anchor.

I used the following equation to calculate the tensile force resulting from the applied installation torque.

F = T/(K*D)

Where

- F is the tensile force.
- T is the torque applied to the anchor nut.
- K is the friction of the bolt contact. (0.2 for steel)
- D is the diameter of the bolt.

- Installation Torque 25 ft. lbs.
- Ultimate Tension 3,480 lbs.

F = 25 ft. lbs. / (0.2 * (0.375 in./12 in. per ft.)) = 4000 lbs.

Again, if my understanding and calculations are correct, the installation tensile force of 4,000 lbs. exceeds the ultimate tension specification of 3,480 lbs.

Please let me know where I am going wrong.

Thank you.

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