Arbitrarily a discussion came about on this issue.
I was surprised by it, and did not particularly think that there were any significant and "strong" thoughts out there regarding this issue.
I was wrong.
The brief poll i took in the office showed that some folks are using the hex head anchor bolts in place/lieu of J or L bolts at all anchor bolt locations (including shearwalls). The thought offered was related to a reduction of J/L bolts per Appendix D.
App D DOES mention J/L bolts, but only in the context of PULLOUT (as far as i can tell).
The basic thought there is that the pullout of the J/L bolt is related only to the projected area of the "hook" portion, and this "area" is multiplied (arbitrarily) by a 0.9 factor. In contrast the hex head bolt pullout is based on a net "brg" area multiplied by a 8.0 factor. This is apparently based on testing results.
Fair enough.
The main issue here is that the J/L bolts are being spec'd in non-pullout uses such as in sole plate applications to shearwalls - NOT for holdowns - which are themselves again subject to the "nuanced" intricacies of the "infamous" Appendix D.
Contractors appear to not "give a hoot" about which type of bolt is used for the "non-PT" cases. Of course they would still like to "wet-stick" things - but that aside - there appears to be no premium one way or another on the anchor bolt issue. They indicate that post install is almost always prefereable using drop in or titen or shot type applications where applicable.
Based on this, we should probably decide how to handle this in our office so we can try to be consistent. It may well be "reasonble thing" to go to the hex-head anchor bolt wholesale. Can we have a discussion on this? Take the poll at least...
I was surprised by it, and did not particularly think that there were any significant and "strong" thoughts out there regarding this issue.
I was wrong.
The brief poll i took in the office showed that some folks are using the hex head anchor bolts in place/lieu of J or L bolts at all anchor bolt locations (including shearwalls). The thought offered was related to a reduction of J/L bolts per Appendix D.
App D DOES mention J/L bolts, but only in the context of PULLOUT (as far as i can tell).
The basic thought there is that the pullout of the J/L bolt is related only to the projected area of the "hook" portion, and this "area" is multiplied (arbitrarily) by a 0.9 factor. In contrast the hex head bolt pullout is based on a net "brg" area multiplied by a 8.0 factor. This is apparently based on testing results.
Fair enough.
The main issue here is that the J/L bolts are being spec'd in non-pullout uses such as in sole plate applications to shearwalls - NOT for holdowns - which are themselves again subject to the "nuanced" intricacies of the "infamous" Appendix D.
Contractors appear to not "give a hoot" about which type of bolt is used for the "non-PT" cases. Of course they would still like to "wet-stick" things - but that aside - there appears to be no premium one way or another on the anchor bolt issue. They indicate that post install is almost always prefereable using drop in or titen or shot type applications where applicable.
Based on this, we should probably decide how to handle this in our office so we can try to be consistent. It may well be "reasonble thing" to go to the hex-head anchor bolt wholesale. Can we have a discussion on this? Take the poll at least...
1 comment:
I would argue for the use of hex head bolts in all locations, for a few different reasons. First, the "belts and suspenders" answer - if there isn't a significant cost or labor difference, it's better to provide a stronger connection in case of future issues. I've had situations where I've gone back to old projects for remodel purposes and had them reuse old intermediate s.w. anchors as holdown bolts rather than epoxy in new ones; obviously a rare condition but if the cost difference is negligible why not?
Second, in many cases we *are* using the bolts for uplift purposes - the base "1 kip" uplift before we throw holdowns in. L and J-bolts can't (by code) handle the shear and uplift simultaneously; they usually fail the interaction check (assuming a distribution of the 1k to three bolts in a triangular load pattern). Hex head bolts will generally pass.
Third - and this is purely anecdotal - I've noticed (on site) that embedded hex head bolts tend to have better pre-pour quality control (that is, they try harder to get them vertical, because the hex head and washer are more noticeable when crooked), and better resistance to being pushed around by concrete (whereas J and L-bolts tend to drift a bit). But like I said, that's purely anecdotal. It may - probably - has more to do with bad contractors and inspectors.
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