Friday Afternoon Dilema!!
Friday Afternoon Dilema!!
(OP)
Ok, I'm working on a metal building foundation project. Obviously I have vertical and lateral loads. Well originally I designed my exterior pad footings for gravity loads only and was going to provide a grade beam/tension tie member across the building to take out my horizontal thrust loads. I ended up with 10x10 pad footings with 16"x16" grade beams w/(8) #8 w/mech splices and ties. I can get 14'x14' footings by taking both thrust and gravity loads into account. I can get a cost estimate on the different design. Will I be happy with either design? I'm affraid that if I design my footings for overturning that I might get unwanted rotation from my footings. An overturning moment of 650k.ft scares me!! Please advise.






RE: Friday Afternoon Dilema!!
Also, why do you need ties in a tension tie? These are for shear. Just embed the #8's and weld or connect them as you mentioned, providing 3" of concrete cover.
Mike McCann
McCann Engineering
RE: Friday Afternoon Dilema!!
Mike
I have often seen (and even used as a company standard) a detail that provides ties in the tension bar splice region. I really can't see any reason for them off hand.
RE: Friday Afternoon Dilema!!
One more thing, why are you worried about the rotation in the footing? Most of the time, the connection between column and footing is considered pinned. which means the footing will experience only tension,compression and lateral thrust from the load combinations.
RE: Friday Afternoon Dilema!!
Normally, for smaller metal buildings, I do use #4 or #5 hairpins in the slab and do cast monolithically.
It's just that for the tension forces ars001 is describing, I think that hairpins (8#8 bars he said) would not work - too many bars, too big, in too little an area to develop the bar tension. I think a lot of cracks would open up in the slab unless they went a long way into the slab. Moreover, with #8 bars, I would really start thinking about a 6" thick slab for the development. Really, I would go with a direct tension tie here as I understand the situation.
ars001: I, too am a little confused by so much moment to the footing. Is the moment due to the footing not being concentrically loaded, or the lateral kick to the pilaster and on to the footing?
Mike McCann
McCann Engineering
RE: Friday Afternoon Dilema!!
Dik
RE: Friday Afternoon Dilema!!
Maybe 2 Dywidag bars would do the trick in the tension tie.
RE: Friday Afternoon Dilema!!
can you tell a bit more about your buildng ! is it single story, whats the span and bay spacing. whats the eave height and ridge height. I am just a litle curious that what size of building brings 650 K-ft momment to foundations
RE: Friday Afternoon Dilema!!
RE: Friday Afternoon Dilema!!
RE: Friday Afternoon Dilema!!
RE: Friday Afternoon Dilema!!
RE: Friday Afternoon Dilema!!
If that is the case the larger spread footings doesn't sound like that bad of an option. Are you thinking of putting a horizontal bond beam at the bottom of the wall to help distribute the lateral forces to the spread footings?
RE: Friday Afternoon Dilema!!
http://www.tensarcorp.com/index.asp?id=99