Ties in concrete columns
Ties in concrete columns
(OP)
We are looking at a project where the EOR has designed columns without intermediate ties as required by the code. Bars are not bundled and details are Column size 32"x32". Single #8 bars at 6" ctrs with only an outer tie. In the commentary to 318-77 there is a suggestion that ommission of intermediate ties could be allowable.
Can anyone shed any light on this
Thanks
Brizstruct
Can anyone shed any light on this
Thanks
Brizstruct






RE: Ties in concrete columns
There was a parking garage that I once worked on where the original construction had omitted some ties and the engineer at the time required the addition of some 3/8" x 2" steel straps to be placed around the square columns. They fabricated the straps a bit short and then heated them to fit around the column hot. The ties were welded to form a complete perimeter square and then as they cooled they tightened around the concrete. Probably not immensely expensive and I would sleep better knowing I'd required it.
RE: Ties in concrete columns
RE: Ties in concrete columns
RE: Ties in concrete columns
RE: Ties in concrete columns
I believe that the ties are required. THere is a need to provide local buckling restraint and the ligs also keep the vertical alignment try.
With lapped splices there is a need to provide restraint for the bars at that point so I didn't see it being a solution.
I was wanting to see if there had been some other research done that anyone else was aware of
Cheers
Brizstruct
RE: Ties in concrete columns
RE: Ties in concrete columns
Does it make a difference if it's a pier and not a column?
RE: Ties in concrete columns
There is no way any concrete construction can go without these cross ties unless you qualify under "Plain Concrete" of Chapter 22. Not sure what your EOR was smoking.
RE: Ties in concrete columns
Ask your EOR how he got around 7.10.5 which expressly requires cross ties. There is no exception that I'm aware of - ask him/her where the exception is. If you get an answer I'd sure like to know where it is.
RE: Ties in concrete columns
I can't see how ties can be avoided as per the standard. The code is explicit and I am yet to find research that would suggest otherwise.
Ties provide
a) Restraint against local buckling of the bars
b) Confinement of the inner core of the concrete
c) Vertical alignment control of the bars.
I beleive that compliance with the code is necessary unless you can argue that the member complies with the Plain Concrete requirements and the reinforcement is additional. (In this case, I think you would be unemployed due to the construction cost)
I did find an interesting paper in the Canadian Journal of Civil Engineering Vol 29 No 6 "Strength and ductility of laterally confined concrete columns"
Thanks for the comments
Regards
Mark Hickey