Anchor Bolt Question

[mduu]

Hello all,

I'm building a 40x60 red iron building kit in Florida. I got foundation engineering and it specifies '5/8" 15" long headed' and '3/4" 18" long headed' anchor bolts. The picture shows a normal looking but long bolt with a hex head embedded into the footing.

Concrete guy says people just drill after concrete and do threaded rod. I looked into it but the epoxy is really expensive.

When looking at the engineering, originally I thought that they meant L bolts. But I have been researching and found that there actually is a distinction that you should use normal bolts with a forged bolt head inverted into the concrete. Despite seemingly having less purchase into the concrete the L bolts can straighten up and pull out while a headed bolt will need to rip a whole cone of concrete out. That's what I read anyway.

So I am taking my 3/4" 18" long bolt with a regular hex bolt head and sinking it inverted into the concrete (attached to a template). To those experienced this isn't crazy right? People really use headed bolts inverted into the concrete (versus L bolts) for uplift resistance? Should I add a washer at the end?

Thanks for all help

 

[wssix99]

So I am taking my 3/4" 18" long bolt with a regular hex bolt head and sinking it inverted into the concrete (attached to a template). To those experienced this isn't crazy right?

This doesn't work. The hex head anchor bolts are special animals and you can't just switch regular bolts...

I got foundation engineering and it specifies '5/8" 15" long headed' and '3/4" 18" long headed' anchor bolts.

You should have some more detail somewhere on the drawings that specify the type, spec and grade of the bolts you need to use.

But I have been researching and found that there actually is a distinction that you should use normal bolts with a forged bolt head inverted into the concrete. Despite seemingly having less purchase into the concrete the L bolts can straighten up and pull out while a headed bolt will need to rip a whole cone of concrete out.

It depends on the specific foundation design. All anchor bolts build up a stress cone in the concrete. The surface area of this cone is a large area where the (relatively weak) concrete resists the larger tensile forces from the bolt.

In situations, like you have here, the bolts can be so deep and the concrete can resist so much force that a regular L or J bolt will straighten up and pull out like a wet noodle before the concrete fractures. In this case, you might need the stronger forged hex bolt.

Engineers will test the design for the concrete's strength, ductile failure of the bolt, fracture of the bolt, shear at the connection and other factors. There's never a one-size fits all design. Being in Florida, you need a really deep/strong connection. (Up where I live, L bolts would probably do just fine for the same building since our hurricanes aren't so bad.)

 

[mduu]

The building kit specifies A307 or A325 bolts. The concrete engineering specifies A36 which is just the grade of steel. As I said above it says 18" long headed. My interpretation is that it is specifying "headed anchor bolt" and indeed the picture shows a hex head. Based on that I bought A307 rated bolts that were actually called "anchor bolts" on the website. I got test data sheets with them too and the tensile strength matches requirements. I am fairly confident in the material itself. That's why I am hoping what I got is correct with the exception of the oddity of embedding a hex head into concrete.

 

[Jarwop]

www.atlrod.com

 

[mduu]

So for anchor bolts that site shows threaded rod and L bolts. Specifically I saw that threaded rod is a no no. It's probably not the end of the world on a small residential building but in a skyscraper or something the threads prevent the full rod from taking on a stretch. Only the upper portion. The top threads break/loosen over time and the bolting eventually becomes loose. A headed bolt with threads only at the top outside of the concrete prevent this.

Aside from that that website shows just L bolts which I am told can and will pull out in hurricane winds, hence the engineer specifying headed bolts.

Also I did the math on the uplift requirements. Depending on how you read it, one bolt can handle the uplift requirements of entire building or a single post. So it's at least 4x safety margin.

Again this is all my understanding and that's why I am here looking for any further guidance. Right now I am still convinced that what I got (https://boltdepot.com/Product-Details?product=126) is appropriate based on the engineering.

 

[readhead]

We have been using headed anchor bolts in my area for at least fifteen years on commercial work and red iron buildings. Some engineers will specify B-7 all thread with a plate double nutted at the bottom but mostly just bolts.

When you make the templates drill 5/8” holes and put a nut top and bottom. Sacrificing the bottom nut will keep the bolts straight during the pour. Cover the threads with tape during the pour to keep them clean. Usually my first extra charge on a job is when we show up to erect the steel and we have to spend several hours cleaning concrete off the bolts.

Don’t assume that the concrete is flat. Shoot the bolt locations and they should all be within 1/4” of each other total. If not you will need to find the highest one and shim the others to it.

 

[Rusted Nut]

We have been using headed anchor bolts in my area for at least fifteen years on commercial work and red iron buildings. Some engineers will specify B-7 all thread with a plate double nutted at the bottom but mostly just bolts.

When you make the templates drill 5/8” holes and put a nut top and bottom. Sacrificing the bottom nut will keep the bolts straight during the pour. Cover the threads with tape during the pour to keep them clean. Usually my first extra charge on a job is when we show up to erect the steel and we have to spend several hours cleaning concrete off the bolts.

Don’t assume that the concrete is flat. Shoot the bolt locations and they should all be within 1/4” of each other total. If not you will need to find the highest one and shim the others to it.

Exactly this!

We installed some 2 1/2” diameter bolts, 12’ long last year; with double nuts and large plate washers. Cover exposed threads with tin foil before pouring, way easier than cleaning off concrete.

OP - follow your engineered plans. Epoxied bolts are not the same as imbedded anchor bolts.

 

[wssix99]

I bought A307 rated bolts that were actually called "anchor bolts" on the website.

Sounds like you have the correct thing.

 

[WNYflyer]

Great reading material in link below. That said, at a minimum we specify ASTM F1554 Grade 36 material for anchor bolts unless loads dictate otherwise. It is a newer spec than ASTM A36 and specifically for anchor bolts. That said your anchor bolts are probably subjected shears as well as tension load. In the end in is up to your foundation engineer to clarify the required anchor bolt material/review a contractor submittal to differ from the anchor bolt material and installation procedure.

Also for what you are calling a red iron building the steel erectors that we typically see will visit the site to verify the already installed anchor bolts are in the correct locations and if any corrections need to be made. They don't move to the site to do any erection until they know the anchor bolt locations are correct.

https://www.portlandbolt.com/

 

[Kaizen]

yea have them put them in when concrete is wet. Can you buy an sds drill and do after with epoxy? Sure but why? Two min vs 2 hours? As said tape end of bolts. I thought you tornado guys down there had to have them wired to the lateral rebar??

 

[nadogail]

Drilled Holes with Epoxy Anchoring is not equal to Anchor Bolts Set into wet Concrete.

 

[wssix99]

Drilled Holes with Epoxy Anchoring is not equal to Anchor Bolts Set into wet Concrete.

If you take the time to read this thread and the great information that the OP provided, you will learn why this statement is incorrect.

 

[bb29510]

The building kit specifies A307 or A325 bolts. The concrete engineering specifies A36 which is just the grade of steel. As I said above it says 18" long headed. My interpretation is that it is specifying "headed anchor bolt" and indeed the picture shows a hex head. Based on that I bought A307 rated bolts that were actually called "anchor bolts" on the website. I got test data sheets with them too and the tensile strength matches requirements. I am fairly confident in the material itself. That's why I am hoping what I got is correct with the exception of the oddity of embedding a hex head into concrete.

307 is a mild steel bolt less than a grade 5, its is usually use for purlins connection, a 325 is a high stremgth bolts and is use for heavy steel beams and columns connection. a36 is you everyday mild steel, anchor bolts are not high strength steel, their only job is to hold in place, not to transfer the load

 

[Hobby_Man22]

I thought they were called J bolts? They're placed in the slab when the concrete is poured. That was practically the first question my erector guy asked me when I said I already had the slab poured. He goes did they put the anchor bolts in place? Yes..... Only time they drill and do the epoxy thing is if they weren't placed in the right spot. They have the cut it off and drill and epoxy it in the right spot.

 

[Hobby_Man22]

Drilled Holes with Epoxy Anchoring is not equal to Anchor Bolts Set into wet Concrete.

They arent placed into wet concrete. You're supposed to make a jig that holds them in place while the concrete is poured.

 

[CraigStu]

I am wonder how the building owner gets involved in the specifics of anchor bolts. Won't the iron building company provide the correct bolts so they or you can provide them to the concrete people? If I had doubts I might also ask the permit inspection dept for your county or whoever is in charge of permitting.

 

[readhead]

The way I do it is the engineer specifies the bolts and the concrete contractor supplies them.

 

[Hobby_Man22]

I am wonder how the building owner gets involved in the specifics of anchor bolts. Won't the iron building company provide the correct bolts so they or you can provide them to the concrete people? If I had doubts I might also ask the permit inspection dept for your county or whoever is in charge of permitting.

There's an anchor bolt plan for the foundation. Says how many and what size needed.

 

[readhead]

Clarification. The building manufacturer will provide a bolt layout plan. The engineered foundation plan will specify the type and length of the bolts. Most manufactures do not include the foundation plan but there are some that do. Some cold formed builders supply the foundation plan.