Anchor Heads

[Leftwow]

I'm a junior engineer, however through my calculations I found that the appendix D specifies pullout strength as the effective area of the bolt head times 8 times the compressive strength of the concrete. SO... then I noticed that square nuts provide more pullout strength than hex head nuts. Do you guys agree? And if you do, why aren't they typically used?

 

[JStephen]

I think the calculations show that a hex nut will provide adequate anchorage, so there's no motivation to use square.
We use welded steel washer plates, which are square, just because they're easier to cut that way.

 

[Lion06]

Hex nuts are most common and the concrete pullout failure mode almost never controls the App. D capacity of a cast-in anchor.

 

[Leftwow]

One engineer told me that the washer plates cause the concrete to crack of the side of the plate. Not sure why, maybe I need to do some more research on this. We were building foundations he refused to use the square plates, but could've just been a load of doo doo not sure...

 

[Leftwow]

Here's another thought, with all respect to older and more experienced engineers, something that is common or typically used for years, does that mean that it couldn't be improved? If course you tell a designer this and he will say "WE'VE BEEN USING THIS FOR YEARS", mainly because he doesn't know why he's using them... more of that's what he knows.