Grade Beam on Piles with Torsional Load
Grade Beam on Piles with Torsional Load
(OP)
I am designing a 4 story building with a basement that will be placed on auger cast piles. The perimeter of the building will be placed on grade beams to support the basement wall as well as a brick facade above. With the exception of the basement wall, the support structure is steel. So, any columns will be placed in the center of the grade beam, but the basement wall and facade will placed to the exterior of the grade beam creating a torsional moment. What is the best way to handle this load? My initial idea was to ensure a moment connection at all pile/grade beam interfaces so that I can assume the beam fixed against torsion at these locations and then design the piles for the additional moment. Does anyone have a better suggestion?
Thanks in advance for any help.
Thanks in advance for any help.






RE: Grade Beam on Piles with Torsional Load
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
BA
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
DaveAtkins
RE: Grade Beam on Piles with Torsional Load
And I try so hard not to make mistakes in this forum
DaveAtkins
RE: Grade Beam on Piles with Torsional Load
BA
RE: Grade Beam on Piles with Torsional Load
The flooring will take out the torsion.
RE: Grade Beam on Piles with Torsional Load
Kinematically speaking the grade beam rotating will induce diaphragm/membrane forces in the slab. However, if the slab is connected to the grade beam by lying on top with a doweled shear connection, shear friction relies on a tiny bit of initial slip, doesn't it? I see the critical task to be to limit cracking in the grade beam. Cracks in non-soil bearing concrete members scare me due to the likliehood of accelerated corrosion of reinforcing.
RE: Grade Beam on Piles with Torsional Load
That is not good idea to have a floating slab (SOG) for the basement anyway.
RE: Grade Beam on Piles with Torsional Load
Whats wrong with a floating SOG in a basement?
Don't 95% of all basements have this?
RE: Grade Beam on Piles with Torsional Load
What I'm getting at is that I wouldn't just check/design the wall and slab for the strength required for the additional flexure - I'd put some consideration into the relative stiffness of those members.
RE: Grade Beam on Piles with Torsional Load
1. To help resist tendency of grade beam rotation.
2. Prevent water infiltration
RE: Grade Beam on Piles with Torsional Load
BA
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
I am not trying to be smart here.
I have built many a home with basements.
All had plain old slabs-on-grade.
Am I missing something here or saying something wrong?
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
If you're putting moment into the top of the pile, then you would need obviously need hooked steel from the pile into the grade beam. It wasn't shown on your detail, so I thought I would throw that out there.
RE: Grade Beam on Piles with Torsional Load
Above all, I don't do residential, even the exception of my only such design was applied to a light industrial facility with odd pre-existing wall footings buried deep into the soil, not much choice there.
I like the solid feel of reinforced floor, no need to worry about joint details/material, cracks, seepage, running mud after flood, and potential of change of use.
After all, the OP's section might not have much torsion after successful back filling. Torsion could be critical during the stage of wall construction.
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
Delete the grade beam. The concrete wall is more than adequate to act as a beam on its own. Instead, use a pile cap at each pile and extend the cage from the pile into the pile cap. Center each pile under the center of gravity of applied loads to reduce moment in the pile. The grade slab can be tied laterally to each pile cap but it does not need to resist moment.
Do you really need 16" thick walls? How is the top of wall tied into the structure? There is no vertical reinforcement on the inside face of the 10" block where it meets the 16" wall, so it can't span vertically. If the wall spans horizontally between pilasters, the pilasters must be tied to the Main Floor structure to resist lateral loads.
BA
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
BA
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
I agree that with pilasters, there is no concern with torsion on the grade beam. I would still use the grade beams, as they give a good platform for the rest of the construction. The pile reinforcement should at least extend a decent length into the grade beam.
At the top, I assume brick veneer continues above. The slab should be carried through to support the veneer backup rather than depending on the 6" CMU.
RE: Grade Beam on Piles with Torsional Load
I agree that the nomenclature on the drawing is questionable. It needs to be revised to make the intent of the drawing clearer.
I don't have a problem with using a grade beam, but a 2'-9" by 3'-0" continuous beam is an expensive way to provide a platform for wall forming. I would not do it and I don't think you would either.
BA
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
RE: Grade Beam on Piles with Torsional Load
What difference would it make if the floor were plain concrete or reinforced as far as seepage goes?
Where is this mud coming from ?
We usually pour basement slabs on a layer of 6 mil plastic.
If you can feel the reinforcing in the slab you must have some sensitive toes!!!!!