Couple on a Grade Beam
Couple on a Grade Beam
(OP)
I need to analyze what is essentially a couple on a grade beam due to column reactions from wind bracing. Can anyone guide me as to determining what maximum moment will be generated in the grade beam? I can determine a modulus of subgrade reaction from the soils report. However, the portion of the grade beam that is in uplift will be resisted by adhesion on the sides. So, i guess the main problem is that I do not really know how to model the adhesion on the sides of the grade beam as a vertical support. Any guidance would be greatly appreciated..





RE: Couple on a Grade Beam
Mike McCann
McCann Engineering
RE: Couple on a Grade Beam
RE: Couple on a Grade Beam
Using adhesion on the sides of a strip footing is not good practice. You should rely on mass, which can include a contribution from soil engaged by the footing projection.
RE: Couple on a Grade Beam
Amen
RE: Couple on a Grade Beam
I would treat it as a cantilever either side of each column ensuring that there is enough top and bottom steel to take the bending. Also check shear.
The bending stress is from the bearing/ the dead load resistance required to resist the loads at each column.
RE: Couple on a Grade Beam
Sorry - just had to say that
RE: Couple on a Grade Beam
Mike McCann
McCann Engineering
RE: Couple on a Grade Beam
RE: Couple on a Grade Beam
You could model this as a continuous beam supported on springs (spring constant based on the subgrade modulus of the soil).
DaveAtkins
RE: Couple on a Grade Beam
RE: Couple on a Grade Beam
That would be "shear" stupidity...
Mike McCann
McCann Engineering
RE: Couple on a Grade Beam
1. determine/estimate the influence area due to the uplift force.
2. compute the resistance force (adh X influence surface areas)
3. if result of 2 is less than the uplift, then add member dimension to increase dead weight or the surface areas, and go back to step 2. Otherwise, the segment of the beam under influence will stay in place, then proceed to 4.
4. reduce the uplift force by the resistance force calculated in 2. This is the force that the beam segments adjacent to the uplift region would feel.
5. in the model, release the springs in the uplift region.
6. repeat the steps 1-5 to adjust the springs until the upward movement in the uplift region is small to nil.
RE: Couple on a Grade Beam
Mike McCann
McCann Engineering
RE: Couple on a Grade Beam
Ha on the couple!
f-d
¡papá gordo ain’t no madre flaca!
RE: Couple on a Grade Beam