column error
column error
(OP)
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RE: column error
RE: column error
RE: column error
Thanks to COEngineer for the photo help!
At last my post---
So, I am inspecting and advising for a job that my firm designed a couple years ago now. This is one of those jobs that was just never meant to be. The general contractor is now on his 4th concrete sub and I consistantly find problems that have to be fixed. The project is now several months behind schedule and last week we learned of a doosie of a problem. Apparently one of the concrete subs decided to pour an extra 6" of concrete on some basement concrete columns to avoid having to use a 2" air space and place 4" CMU blocks below grade. When this was done a brick ledge was not left below grade thus the general contractor began cutting away what should have been excess concrete. It wasn't long before the general contractor discovered that there were major reinforcing problems as they discovered what is shown in the picture below. They found this condition at around 10 columns. The ledge is 4" wide at the moment and the height from the ledge to the top of the concrete is approximately 22". The reinforcement is placed such that there is almost no cover. The concrete columns are supports for steel tube columns which continue up to a two story height above grade. It is our suspicion that no reinforcing exists in the top 22 inches of concrete. Additionally, everything is already load bearing and all steel is up. I could go on, but I will stop for now and answer any questions as they come. We are looking for a creative solution for this problem that is "relatively" economical. Any advice/ideas at all will be appreciated.
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RE: column error
RE: column error
RE: column error
RE: column error
Anchor Bolts: 2 3/4" Dia. A325 Anchor Bolts Specified with 12" embedment, cast-in-place, 3000 psi concrete, spaced 5" apart on each side of a 4" tube column. (Note: contractor placed 4 anchor bolts in compliance with OSHA requirements)
Obstructions: Just the 8" CMU walls on each side, concrete column is flush with outside face of wall.
Column Load- exact from calcs unknown (not my design, but another person from my firm) however this is a library and there is one story and a roof supported by the steel column. Floor system is a steel beam and joist system with concrete deck 3" total height on 1" 26 GA steel form. Approx 200 SF of trib area. My quick approx is around 25psf dead and 150 psf live(floor) and 20 psf live(roof). Thus, a total load of approx 45 kip.
CMU walls: 8" block with #4 @ 48" o.c., grouted only at reinforcing.
RE: column error
RE: column error
RE: column error
Another alternative that we thought about using was to straddle the column with two horizontal beams near grade. The ends of the beams were to be supported on mats, one inside the building and one outside. This was nixed in our case because of real estate limits.
I have a cool close-up picture of the pedestal and footing formed up with reinforcement installed with the column and anchor rods in it just hanging there. I tell people that see that picture that we installed the steel before we poured the concrete...
RE: column error
RE: column error
1. install adjustable screw shores under each spandrel to transfer all the floor and roof gravity load into the perimeter cmu walls. Space your jacks out beneath the spandrels as required. The steel column can now "hang" on shear connections to the spandrels.
2. Demo the as-built concrete pier down to the top of your footing. Keep col anchor bolts in place. (You might consider keeping the part of the pier below the brickshelf el, but it may be best for peace of mind to take out the whole pier).
3. Install new reinforcing for the pier.
4. Form and place concrete up to within 3/4"+ of the bottom of baseplate. Use foam blocks to form your brickshelf.
5. Place non-shrink grout under the baseplate.
Engineering and judgement are required at every step. Good luck to ya.
RE: column error
Thanks to everyone for the great responses! I expect we settle on a fix in the next few days. I'll be sure to post our solution so that you know how this turned out.
RE: column error
If those are truely columns (weight of column > 300#) then per OSHA they have to have 4 anchor rods( anchor bolts). Only if they weight less than 300# can they have 2 anchor rods.
RE: column error