UPSET GRADE BEAM

Rittz:
Can you get a few cross walls (shear walls) in that bldg. at 40' or 50' o/c, or some module which matches their storage racking layout. I assume there is an isle down the middle. Kickers btwn. the studs and the bottom chord of the trusses might help. The buttresses and extra conc. pile seem kinda like overkill, in that they probably do not really take advantage of that expensive extra pile. Would there be any advantage in making the main piles a little larger in dia. for their improved upward cantilever cap’y. and rebar space. Then haunch the grade beam down a few feet on either side of the pile to improve is upper lateral resistance. They are tied together with rebar, of course. At the 20' spacing of the main piles, could you cast a 70' long tie beam, under the slab, btwn. opposing piles. This might also be a nice module for slab pouring and slab const. joints too.

You have to resist the overturning due to the reaction at the top of the concrete wall. Trying to do that only at the 20' intervals seems counterintuitive. Better to do it all along the wall with an appropriately sized footing.

Hi Dhenar

Thanks a bunch for the response.

Apparently the owner does not want partitions (shear walls) … just a wide open floor space. Could we perhaps make the building a bit shorter to ensure a successful plywood roof diaphragm (blocked at all edges).

The other issue of the wall cantilevering upward 4 ft could maybe be handled with
one larger pile (instead of the buttress and 2 piles as I showed) along with 70 ft beams from side to side every 20 ft and haunching down the grade beam to reduce the lateral pressure on the earth. If I’m visualizing the “haunching” as you do.

The upset grade beam will experience some torsion from the reaction at the intersection with the wood wall.

Depending on what your torsion calcs yield, it may be more economical to cast the grade beam below grade with a section size better suited to accommodate the torsion and simply cantilever the 4' stem. Adequately sized piers at 20' spacing should be able to handle the moments and lateral loads induced. At least this way you only need to form one smooth wall and not worry about having to place torsion reinforcing (closed hoops?) in what would hopefully be a fairly thin wall.

The drawing shows 16" dia. piles, 16' long at 20' centers. Are these to be friction piles? If so, you probably need more piles or deeper piles to carry the gravity load. If piles are spaced at 10' centers, it should be possible to achieve an adequate connection between piles and wall to resist moment from wind on the upper wall.

The roof must be adequate to act as a diaphragm so that wind acting on the upper half of wood wall and roof is transferred to the end walls. If it is not, you may want to provide a horizontal truss in the plane of the bottom chords of the trusses.

BA

Thanks for your response BA. I appreciate it. I should retire too but I hate shopping for groceries and I did retire from golf .... can't shoot my age .

Yes the piles are friction cast in place concrete ... the depth and dia. shown are only pictorial so far. I like your idea of 10 ft spacing and we do have a soils report. (highly plastic clay) The torsion shouldn't be a problem and the moment at the pile/wall interface should be routine as you say

JR

Rittz:
You could sheath the underside of the trusses, as well as the roof planes, for more diaphragm action, and it will also keep the bird nesting to a minimum. You could make the trusses with a 24" high (or whatever) heel and actually make something of a moment connection btwn. a spaced double 2x8 studs. You got my drift on the downward haunched grade beam, to pick up lateral soil pressure area around the piles. Certainly, Hokie’s suggestion of footings for their distributed hold down and lateral ability is a likely option. And, you do have 4' to 6' frost cover requirements up in your neck of the woods, don’t you? Maybe a benefit for hold down and lateral standpoint. I don’t envision the upturned grade beam in torsion, as much as bending laterally btwn. the piles or as a cantilevered retaining wall of sorts, although it is loaded on the top edge. You may want some hold down hardware btwn. the top of the grade beam and the 2x8 stud wall, plus its sheathing or siding covering. Maybe a strap from the conc. wall up onto the stud at each roof truss. With the large door openings in the end walls, you might pay hell finding enough shear wall cap’y. with only two walls.

I have a friend who regularly shoots his age, but he's 89, so he doesn't think it's a big deal.

BA

Cant you design a cantilevered retaining wall off the piles with the wall reaction at the top? If need be use concrete ties across similar to a metal building