ACI Appendix D- Bolt Tension Calculation

[maneesha0702]

I have two questions regarding Anchor rod.
The first question is if I use a sleeve will the effective length decrease by the sleeve length.
The second question is
a)if you use 4 bolts ( bolts are equidistant in both directions)and if the wind is acting perpendicular to two adjacent bolts what is the lever arm? Is it half the distance between bolts?.
b) What happens when the wind is shifted by 45 degrees ( ASCE quartering of winds)? Will the tension be seen in 1 bolt or 3 bolts? What will be the leverarm if it is one bolt? What will be the leverarm if it is three bolts?

 

[Guastavino]

For #1, does the anchor rod have a head on it? How is it being installed?

2a)I think I know what you're getting at but a sketch would help. This can be pretty complicated to describe. Try using software I mention below and it has calculations you can print out and study to show you. how that is calculated out. It has some great sketches too that the detailed report spits out. Then you can kind of see how it all works and get a good feel for it.
2b)Resolve the load into two components (one in each direction) and analyze it in both directions independently, then use superposition to get net tension and shears.

Hilti has some free software that helps with this. It's called Hilti Profis anchor. Good stuff.

 

[mike20793]

1. The effective length is the length of anchor rod that is bonded with the concrete.

2a. Resolving the moment will give you a force couple with half the bolts in tension and half in compression, so the moment arm would be the distance between the rods in the direction of loading

2b. Same as mentioned above.

Profis is good and so is the Simpson program. They are basically the same, but I do prefer Profis since it can do embed plates (studs, not the plate itself). Simpson seems to be a little bit faster.

 

[KootK]

1) the effective length represents the depth of the concrete cone that you'll be mobilizing. As such, I believe that the effective depth is to the bottom of the anchors as usual.

2) The answers above suggest that the compression component of the base reaction will be provided by the bolts rather than the concrete. Some detailing arrangements make that possible but it's not the norm in my experience. When it is concrete that supplies the compression, superposition goes out the window for bolt tension and the problem becomes more like the design of concrete columns for biaxial moment.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[maneesha0702]

Thanks a lot for all the replies.