Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Horizontal thrust in rigid Frames ... pre-engineered steel buildings
(OP)
What kind of rod do you use? and how do you protect it from corrosion? When would you use hairpins in the slab for thrust resistance instead of rods?
BTW We use cast-in-place conc slab and grade beam for foundation. More often than not we are in high plastic clay in this area.
BTW We use cast-in-place conc slab and grade beam for foundation. More often than not we are in high plastic clay in this area.






RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
I'm a little confused by your question. Maybe I'm just having a dense moment, but please explain.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Dik
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
See attached sketch
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
1) Cast the bars into a concrete tie beam to allow reinforcement development. Separate from floor slab.
2) Use tension couplers on the bars, then perhaps wrap with Denso tape.
3) Use strand in plastic duct, stress and grout.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Dik
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
We use similar to dik's description....sometimes hooked dowel bars from footing into slab in addition to hairpins...we don't often use grade beams for PEMB's.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
As Hokie66 says it should be seperated from the slab.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
For larger thrust, I use reinforcing bars encased in concrete, under the slab. I detail hooked bars extending out of the column pier and lapping with the bars under the slab.
DaveAtkins
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Hokie66's described method is what I try to use. It reduces the chance of the above and also reduce cracking in the slab.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
1. To account for differential settlement between the column foundations and the concrete slab a length of pipe insulation can be wrapped around the tie bar before being cast into the slab. This will allow vertical displacement without cracking the slab.
2. Because structural loads are being placed in the slab, ACI 318 design is mandated. Standard SOG design will not pass muster for US jobs. This includes rebar spacing, clearances, and shrinkage reinforcement.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
I have always used Jim Fischer's recommendations in the Butler Foundation Design and Construction Manual. He feels this tie below the slab is not really a reinforced concrete member, and therefore is not covered by ACI. Also, extensive testing has shown that lap splices surrounded by stirrups can take repeated loads.
rittz--
The Butler Manual limits hairpins to 27.4 kips (this would be with a #8 hairpin).
DaveAtkins
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Butler Canada tells me the Butler Foundation Design and Construction Manual has not been printed for quite some time. Any chance a copy may be available in the US. Is it many pages or reasonably scan able? Thanks for the info you posted in any event. We appreciate your response
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
I would consider >40 kips to be a very very large thrust for PEMB.
When I suggested not using hairpins for small thrusts, I was thinking in the <8 kip range. Sometimes I run grade beam reinf cont thru the footing and use that as confinement steel and go without hair pins for higher thrusts.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Also regarding heave ... our main concern is from heave and subsidence (due to highly plasic clay) which varies with the seasons and thus with the moisture content. We seldom never use (read .. never )a strip footing with a strip "frost wall" or pad footings the cols and grade beam. We use a grade beam supported by cast-in-place concrete friction piles or driven timber piles or screw piles.
RE: Horizontal thrust in rigid Frames ... pre-engineered steel buildings
Yes, I have used that system of tie rods. See my post above. To the piling options you gave, I would add bored piles. Using two piles at each column gives you enough moment capacity to at least partially fix the base.