Threaded Rod Thru Bolt Shear Strength in 3 wythe brick wall 2

[zrck99]

If you use a thru bolt in a 3 wythe brick wall, how would you determine the shear capacity of the bolt? I assume you would use the bearing strength of brick, the diameter of the bolt and some other safety factors. Has anyone seen this discussed in the codes?

Thanks

 

[KootK]

Thru bolting is kind of a weird thing. It makes gobs of sense intuitively but, at the same time, there aren't really any accepted procedures for analyzing it (that I know of at le

https://ca-prod.asyncgw.teams.micro...5166ac2e2030735/views/imgpsh_mobile_saveast).

In the past, I've seen folks do things like assuming that the bolt bears over six diameters against the brick etc.

My preference nowadays is to avoid thru bolting altogether. That, for two reasons:

1) Analytical convenience. You probably can quantify the capacity of an adhesive anchoring system robustly.

2) Performance. It seems to me that adhesive anchoring system work at least as well as thru bolting, at least in quantifiable ways.

And no, I don't work for Hilti etc. Although sometimes I think that I might like to.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[milkshakelake]

It's hard to determine the bearing strength of brick. You have to lab test it when it's old construction, but even if you do that, you have to decide what code to use. You mentioned codes. The latest masonry code might not apply to old bricks because quality control was different before the code was written.

I prefer not to deal with that. Like KootK said, there are manufacturers that have published reports of the shear capacity of post-installed anchors.

But if you have to do it, I'd rely on what was already installed in that place, because those things are load tested already. Are there any existing thru-bolts in the wall? Probably not. So I wouldn't do it because of a lack of evidence.

 

[Tomfh]

Personally I’d never trust a proprietary glue in or mechanical anchor ahead of a thru bolt.

In what ways can a glue or mechanical anchor outperform a thru bolt?

 

[EdStainless]

Tom,
With glued anchors you know what the rating is, so you can design.
With through bolts and old brick you end up making all kinds of assumptions and approximations and end up with what?
It is just a matter of being able to quantify things.
Yes, the through bolt is likely stronger, but you don't know how much.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Tomfh]

Yes, but how can thru bolts be worse? If you’re prepared to accept a glue in-anchor, what reason is there to reject a thru bolt?

 

[KootK]

Yes, but how can thru bolts be worse?

Has anybody said that the thru bolts would be worse? That said, I can think of one way in which a thu-bolt might be worse, depending on the installation procedure. In predominantly shear loaded applications, you're relying on your anchor bearing against the substrate near the the loaded surface. An adhesive solution will generally create a nice condition there for relatively uniform bearing of the fastener against the substrate. Additionally, the adhesive will act to kind of hold the substrate together where the load is applied. If through bolts are installed with just the anchor sitting in the raw, drilled hole, these benefits would not accrue and I'd expect a decrease in performance owing to stress concentrations. That said, I've known engineers to thru-bolt but do so with the installation of some kind of adhesive/grout as well to help ameliorate stress concentrations.

If you’re prepared to accept a glue in-anchor, what reason is there to reject a thru bolt?

As mentioned above, many of us work in jurisdictions where we have to demonstrate to local building officials that things work. Where that is the case, it is much easier done with the adhesive anchor systems for which test data and established evaluation methods exist.

For probably the last decade at least, I've been asking the following on this forum regarding thru-bolts:

1) Is there relevant testing available to validate calculated capacity?

2) Is there an accepted design procedure for evaluating the capacity of thru bolts? All that I've ever seen is punching shear-ish checks on the back side and something to the tune of uniform bearing over six anchor diameters for shear. That's hardly rigorous and even that I've not ever seen in print anywhere. It's fun to design based on fundamental principles. However, much recent experience with concrete anchorage design and Northridge moment frame connections has taught us that we suck something fierce when it comes to doing accurate connection design based on first principles.

@Tomfh: if you have answers to either #1 or #2, it would pretty much make my week to hear them.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[Celt83]

There are a few resources for the dowel bearing side of it:

Mathematical Models for Dowel Action Under Monotonic and Cyclic Conditions - E. N. Vintzeleou and T. P. Tassios

American Wood Council - TR12

Guide to Dowel Load Transfer Systems for Jointed Concrete Roadway Pavements - Snyder

I'd be inclined to go with an adhesive anchor into existing brick for the reasons KootK noted. All the big providers are more than happy to go to your site for a few hours and load test their anchors. The anchors into solid brick are all tested to the same standard which requires a minimum of 3-wythes so keep that in mind, a lot of the stuff around me is only two wythes so we're usually asking for testing pretty frequently and then assigning our own safety factors.

Edit: BIA - Tech Note 44 has this to say on through bolts:

There are no known published reports available
addressing the strength characteristics of through bolts in
brick masonry. However, based on the conservatism in
the allowables for bent bar anchors and proprietary
anchors, the allowable load equations should provide
acceptable allowable load values for through bolts used in
brick masonry. The embedment depth used to calculate
the allowable load values should be taken as equal to the
actual thickness of the masonry

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[T_Bat]

Here are a few articles on through bolts with some testing results that were in Structure Magazine.

Link

Link