Steel column hairpin rebar 2

[enriko12]

Hi,

We are working on the old steel building with no original prints available. After contractor removed the old slab, there were hairpin rebars wrapped around column pedestals. I understand their purpose is to provide "some" lateral resistance. Anyone had previous experience with those being damaged/removed and any adverse affects on the structure? How useful are those anyway? It's not like they are going to tie 2 sides of the moment frame together. Control joint are typically cut into interior slabs, so hairpins will rarely tie into more than 1 tile, and sometimes joint are cut right through that rebar. Also, slabs are typically poured last, so those are definitely not helping with any dead weight. I am thinking that single slab tile would add a negligible lateral resistance in comparison to that of the buried spread footing/column pedestal/wall footing.

Any input is highly appreciated!

 

[enriko12]

 

[enriko12]

Do you know if there is any steel in those walls? Maybe in the 8' walls but maybe not in the 4' walls (or at max 2 #4 horizontal bars in the foundation walls and maybe 2 more #4 or #5 bars in the strip footing under the walls).

You were right on point! 8' wall (it actually turned out to be 6'8") does not have much steel in it. After examining a construction joint over upper 4ft, I was able to locate a single horizontal bar (#4 or #5) about 6" down from the top.

Jim, you seem to be very familiar with typical 1980s construction. I guess I should not expect any vertical bars in those walls. How about connection between strip footing and a wall? I guess no Ls, but may be a shear key?

 

[jimstructures]

seriko12,

The amount of steel rebar in the concrete foundation walls is complete guess work unless you have drawings or witnesses. There maybe a horizontal bar at the top of the wall, there maybe a horizontal bar above the joint between the strip footing and the foundation wall, there maybe a horizontal rebar at mid height of the 8' foundation wall, there maybe a keyway but probably not, there may be short stub bars between the strip footing and the foundation walls or there maybe longer vertical rebar spaced along the foundation walls on 24", 36" or 48" centers or there maybe no reinforcing bars at all in the foundation walls. there are probably rebar cages in the piers with hooks at the bottom sitting on a rebar mat in the pad.

Non-destructive testing would be required to make an educated guess, unless you have a witness or a contractor you trust.

The anchor bolts are probably two 3/4" bent or J bolts at each column or they maybe 5/8" anchor bolts depending on the size of the building.

Jim