tilt up wall design help

[cris300]

Hi i need help with the tilt up wall design

rules or tables of experts that work every day, in this area
my projects are industrial building with one only floor

what design method your prefer? aci , slender method ..?

i have this questions little confuses

- whats are the minimum ratios of reforment
vertical an horizontal because this elements work as flexural member?

i think that using a shear wall ratio by the aci is an over-reinforcement
because the lateral shear is minimun what you think about this?


-and is possible that using the steel grade 40, the tickness results
smaller than using steel grade 60? similar that the slabs?

i want to desing a funtional but an ecomical wall too

thanks in advance

 

[TXStructural]

Go here (

http://www.tilt-up.org/resources/)

and get the Engineering Tilt-Up book. It is brand new, and will help you do a good job the first time.

I would encourage you to add a little more than minimum cover, especially on exterior faces, as we have seen some older panels with very thin clear cover (3/4" is permitted) not perform well over time.

 

[frv]

I don't think these are set in stone, but generally the thickness of the panel is going to be the same as the width of 2x dimensional lumber (5.5", 7.25" being the two most common).

I suggest you don't go to the bare minimum reinforcing because it's not uncommon to come back a few years later and add new openings; a little extra now can save a great deal later.

You obviously have to run your numbers, but for single story tilt wall jobs with parapets, #5 @ 12 vertical w/ #4 @ 12 horizontal is usually plenty. Again, just a general number to get a feel for it. You can certainly reinforce it less in many cases and must reinforce it more in some other cases. Additional good detailing practices: (2) #5's around entire perimeter, including corner bars. (2) #5 top, bottom and sides of openings, as well as a diagonal at each corner of the opening. At concentrated loads (joist girders, beams) you can embed a pilaster into the wall; at a 5 1/2" panel, you'll probably have to bump out the panel at that location.

After much internal discussion, our company has determined that as of ACI 318-08, the minimum f'c for tilt walls is 4500 (as it is usually exposed)- that could help a little bit with strength calculations.

If you have any say in the size of the panels, try to keep them under 85-90 kips (though this may vary locally); this is because you want to be able to erect the panels with a single crane and that's usually the upper limit we work with.

Design for erection stresses is usually left up to the subcontractor (in my neck of the woods). If they need more reinforcing in the panels or strong-backs for erection stresses, they'll make sure it gets added.

Make sure you assume a thinner section if the architect is showing a reveal (this can be pretty important); e.g., if you have a 7.25" panel, but the architect is showing 3/4" reveals (a common depth), assume you only have a 6.5" solid wall.

And take TXStructural's advice- get the information. I just wrote the above summary because when I started doing tilt wall, I had no idea what "normal" looked like.

 

[JedClampett]

One tip that was passed onto me, was to use standard lumber dimensions as increments for tilt up thicknesses. For instance, a 6 x is 5 1/2 inches tall, so start with 5 1/2 inch thick tilt up. An 8 x is 7 1/2 inches tall, so you next thickness up should be that.
Also, another approach that worked out well is factory made tilt up. The panels are limited to 12 feet wide for shipping, but the contractor doesn't have to mess around with them. Speed Fab Crete in Ft. Worth (

http://speedfabcrete.com/)

was real good, but I'm sure there's a lot of other ones out there.

 

[frv]

Jed,

That would be considered precast. The point of tiltwall is not having to transport anything; you cast the walls on the slab, lift and go. Precast does offer some advantages, including the use of prestressing strands, but I don't think any of the rules of thumb I gave above necessarily apply to precast. Note that the width of a 2x8 is 7 1/4", not 7 1/2".