Grade of anchor bolts

[Schambach]

When specifying anchor bolts to attach steel columns to concrete, everything I read suggests specifying ASTM F1554. I have specified Gr36 and my supplier says that it is much easier and cheaper to get ASTM A193 B7 bolts. Those I read are not as ductile and are stronger. What would preclude me from specifying a B7 bolt then? Am I missing something that would say that I shouldn't?

 

[JLNJ]

Those A193 B7 rods are north of 100 ksi yield. IIRC, they are also an alloy which is less likely to rust. High-spec material.

I can't imagine that they are cheaper, but who knows with these supply chain issues. You might ask about the availability of Grade 55 bolts. Usually those are available and relatively cheap.

 

[phamENG]

Heads are likely to be a different size, so be careful with your pullout calcs. I'd have to dig into them to see if there's another reason not to.

 

[Schambach]

Thanks. I used the wrong terminology. I meant to say threaded rod. I'm using plate washers and nuts for the "head."

 

[dik]

I use a lot of anchor rods and not 'L' or 'J' type bolts and I don't use plate washers on the bottom. Unless required for specific loading, they do little good. In Canada, we spec G40.21-350W or 300W. I also include as an alternative ASTM F1554 Gr 55 S1. Gr 36 is almost the same price as Gr 55 S1 and Gr55 is a lot stronger. Because of past issues, I like anchor welds to be weldable. Your A193 may not be. I never rely on strength to provide corrosion resistance... if there's a possibility that corrosion exists, I spec HDG or something of that ilk. I don't use ASTM A307; unless spec'd as weldable, it isn't necessarily weldable.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[RWW0002]

Steel Manual Table 2-5 mentions use for anchor rods with temperature and corrosion resistance characteristics.

I have never used or specified ASTM A193 B7 material and you are right to look into ductility (especially if this is a design with high seismic requirements). At the end of the day as long as it meets your project strength and ductility requirements, I am not sure there is anything that dis-allows their use.

Here is an article that discusses some other issues

https://www.portlandbolt.com/technical/faqs/a193-b7-anchor-bolts/

 

[dauwerda]

ASTM A193 B7 is often dual certified as F1554 Grade 105 (not always though).

In my experience F1554 Grade 36 and/or Grade 55 are definitely cheaper and usually more readily available than the higher strength material, but I've never had an issue getting any of it from our typical suppliers.

 

[dik]

If it's the same as F1554 Gr105, it's definitely not weldable.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Schambach]

The reason I've taken a liking to the plate washer idea is because of the use of the Simpson Anchor Designer program which employs those. I am NOT in a high seismic zone so I don't see ductility as a huge deal.

 

[dik]

In general, plate washers don't contribute a lot and if you have a bunch of them, they can introduce a plain of weakness. If you can run the anchor rods with and without the plate washer, check the difference in capacities, as an exercise.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

If you can run the anchor rods with and without the plate washer, check the difference in capacities, as an exercise.

This only works if the program considers the relative stiffness of the nut vs the washer. If not, and it only looks at area, the plate washer will look good. My concern is when there's a nut on top of the plate - seems to me that it would create a failure cone above the assumed cone at the washer. Because the nut will be much stiffer than a plate with a larger diameter, that cone would have to fail to allow the assembly to move and engage the full plate washer. By that time, the larger cone doesn't really exist since the middle of it has failed.

I haven't run actual numbers on this - just an intuition thing.

 

[human909]

In general, plate washers don't contribute a lot and if you have a bunch of them, they can introduce a plain of weakness. If you can run the anchor rods with and without the plate washer, check the difference in capacities, as an exercise.

My understanding that research has shown that plate washers perform better than 'L' bent rods.

use a lot of anchor rods and not 'L' or 'J' type bolts and I don't use plate washers on the bottom

Do you use just plain threaded or deformed rods?

I'm just curious. I won't claim great expertise on this.

 

[phamENG]

Do you use just plain threaded or deformed rods?

Can't speak for dik, but I just call for a heavy hex nut if threaded rod is used. It's effectively the same as a heavy hex head bolt but can be cut on site from longer stock. Just have to watch concrete thickness as the size of the nut and protruding rod below your bearing surface is deeper than a bolt.

 

[driftLimiter]

This only works if the program considers the relative stiffness of the nut vs the washer. If not, and it only looks at area, the plate washer will look good. My concern is when there's a nut on top of the plate - seems to me that it would create a failure cone above the assumed cone at the washer. Because the nut will be much stiffer than a plate with a larger diameter, that cone would have to fail to allow the assembly to move and engage the full plate washer. By that time, the larger cone doesn't really exist since the middle of it has failed.

I haven't run actual numbers on this - just an intuition thing.

I discovered recently that Hilti profis also neglects any contribution of plate washer in concrete breakout calculations. Perhaps for the same reasons you mention here.

 

[dik]

I agree... I haven't used bent 'L' or 'J' anchor bolts in decades.


I use plain BAR, threaded and give the fabricator the option to use threaded rods if he wants... also always use heavy hex head nuts. Unless the anchor rods are short, then sometimes use plate washers... I generally us 20 x dia as min length, they are amost as good as plate washers. I seem to recall an AISC paper a decade back that indicated that for high strength rods, the length should be about 17 bar dias. I've encountered a few failures where the plate washer created a plane of weakness. One of the more interesting, the anchorage in question had 6 fasteners terminated at the same level... almost like putting a cold joint in place.

This was used on a recent project where the client wanted to use a double nut... if req'd, I prefer loctite... They put the rod in a vice and peen the end of the rod with a large hammer... no welding...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[human909]

Can't speak for dik, but I just call for a heavy hex nut if threaded rod is used. It's effectively the same as a heavy hex head bolt but can be cut on site from longer stock. Just have to watch concrete thickness as the size of the nut and protruding rod below your bearing surface is deeper than a bolt.

Makes sense.

I agree... I haven't used bent 'L' or 'J' anchor bolts in decades.

It seems that my locality is moving slowly away from L-bent rods but only slowly. I still seem them being detailed on drawings by others.

I get enough odd looks from contractors from plate washers and get ever odder looks on the few occasions I've specified just hex nuts. (I've never been crazy detail orientated on anchor bolts as generally I have been dealing with deep rafts and plenty of excessive capacity provided by the anchor bolts. I would describe my concrete expertise as fairly low but I'm slowly doing a little more here and there. Steel is my day to day work.)

 

[dik]

I design connections for a metal fabricator and seal shop drawings... about 90% of the work I come across still use J bolts... If not shown then I set headed anchor rods for the EOR to confirm the use.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

I still speck L/J bolts for residential work - most residential contractors get confused and swear a headed bolt can't possible be as strong as an L-bolt. I gave up trying to explain it to them long ago. Commercial/Industrial work gets threaded rod with nuts or headed bolts.

 

[dik]

So, how do you put a plate washer on a 'J' bolt?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[canwesteng]

The size of the head or the plate washer shouldn't affect the breakout cone. It would only affect pullout capacity. I err on the side of not believing you can pull the anchor out without pulling out the washer, but where this is a concern I've always used thick washers.