Anchor Bolts for Moment Frames
Anchor Bolts for Moment Frames
(OP)
Our firm always provides over-sized base plate hole for anchor bolts, which is accepted industry practice as far as I am aware. However, our details indicate the same condition for columns part of moment frames with our any modification. So, I modified the detail for the moment frame base plates to include heavy washers welded to the base plate. However, when the project was reviewed internally, they said that "we don't do that", but they weren't clear why it was OK not to provide that detail. I am a bit confused by this, as I am not aware that there is a standard for pretensioning ASTM F1554 rods to develop shear in the faying surface. The detail has no other provisions (shear lugs, etc.) to develop shear, so I don't know what I am missing.






RE: Anchor Bolts for Moment Frames
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anchor Bolts for Moment Frames
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anchor Bolts for Moment Frames
Not so sure about the friction part. I understand, but I didn't think that is was a code-acceptable practice.
RE: Anchor Bolts for Moment Frames
The only time I have seen your detail used was when the vertical load was too small to develop enough friction to hold.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Anchor Bolts for Moment Frames
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anchor Bolts for Moment Frames
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
10-20 years from now, there will be someone posting about how their firm doesn't specify to fill flush the rest of the over-sized baseplate hole with _____________, before placing the washer and nut. "Those guys still have an air gap between the grout and welded washer elevations.... at the very point where the plate wants to load the rod... craziness?!"
While you are discussing anchor bolts, try to work in specifying 2" projection over the nut into details to cut down on the short bolt field problems.
RE: Anchor Bolts for Moment Frames
I have always seen and used the projection above concrete, it seem like nonsense to do anything else.
Going back to the friction thing. In general, the force is applied high enough on the structure that the tension in the bolts and the increase in compression force under the plate are multiples of the applied force, providing ample friction without even considering the DL and LL contribution.
I did use shear lugs where needed.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Anchor Bolts for Moment Frames
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anchor Bolts for Moment Frames
projection over concrete sounds good for concrete foreman, but if i called out to the internet a #-inch projection above the concrete, i would have fished out a few "why does this (geotechnical) feel like he has something to say here" comments because of all the variables.
RE: Anchor Bolts for Moment Frames
RE: Anchor Bolts for Moment Frames
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Anchor Bolts for Moment Frames
1. It is not inconceivable to rely on some friction, if justifiable and continuously available (permanent DL), for low shear loads.
2. Friction is a likely "no-no" for seismic-controlling loads
3. It sounds like some people at my firm are assuming...we all know where that can lead.
4. I should change the title of the OP to "darn SE's and their under-projected anchor rods"
RE: Anchor Bolts for Moment Frames
Now that renaming the title per item #4 as proposed by the OP, i will go to the well one more time with immunity to threadjacking charges.... i know a few superintendents who specifically request their fabricator supply additional threaded length when they put the order in. On 1 job i recall the bolts sticking out about 5" or so past the nut. I did most of the pre-pour inspections on the bolts but that only partially relieved my worries when the first columns were hung and the SE told me on-site that there was no way there was enough embedment and then took me to see the GC. The super showed the order and took us to the laydown area to measure some unplaced rods. He looked like he really enjoyed proving the base assumption of the engineers was wrong.