Anchor bolt into concrete slab

[Samahok]

Hi I am working on a project right now that requires a wooden nailer to be anchored around the roof perimeter of a building, however, I cant find any literature or specs on depth of the bolt into a concrete slab. The only information that I can find deals with anchoring into concrete masonry units (CMU) which requires an 8 inch bolt depth spaced at 4 feet spacing, but the concrete slab is much stronger and I only have a 5 to 6 inch thick slab so 8 inches would not work for my particular application. If anyone has a tip or where I could go to find the information I need, it would be greatly appreciated.

Thank you,

-Sam

 

[JedClampett]

This is a little more complicated then it looks. The anchorage needs to resist uplift and shear forces. It's not as easy as picking one off a chart. Ther's differnt size bolts, spacing and embedment.
You need to get a structural engineer to evaluate this and help you.

 

[Samahok]

That is kind of where the problem is, the engineer who designed this project did a very poor job. His plans just call of an anchor bolt meeting 80 mph FM uplift requirements. However, code requires design for at least a 120 mph uplift, and even suggests a 135 mph requirement since I am in Hawaii and it is considered to be a high hurricane risk. With that being said, the perimeter wind uplift rating that I calculated was 120 psf and the corner rating was 180 psf. My problem now is that I don't know how to take that information and correlate it to 1/2" diameter bolt depth into concrete. Any suggestions?

 

[JAE]

Yes - suggest you hire a structural engineer.

 

[Samahok]

ok thanks anyway...I was just trying to avoid making the engineer who came up with the design look bad. but I guess that what he deserves when he just writes "use acceptable anchor bolt" in his plan and specs

 

[MrHershey]

Would need to take the effective wind area, multiply by your uplift pressure and then go through Appendix D of ACI 318 to check a variety of limit states, which isn't exactly easy or straightforward. Definitely would contact (another) structural engineer to look at this.

And since the job's in Hawaii, *slides business card across table*. I can empathize. There's a lot of not-so-good engineers and architects out here. Really a shame given the hurricane and seismic risks.

 

[JedClampett]

Or you could ask the original structural engineer what his uplift and shear forces were. He's not going to admit he never did them, so he'll either look them up for you or calculate them. I don't think that is embarrassing at all. And the worse he could say is "no" which is kind of an indictment of himself.
Once you have those, it makes the job a whole lot easier.

 

[ZZ2002]

You can reduce embedment (upto min depth per manufacturer's recomendations) by reducing spacing between anchors (eg. from 4'OC to 12"OC). You need to know also existing base mterial strengh f'. May be the roof slab you are looking is light weight concrete. Refer to Simpson or Hilti product manuals. They have also free software to design anchor bolts.

 

[dik]

and make sure you secure the studs to the bottom plate accordingly, by sheathing and/or 'hurricane' ties...

Dik