Foundation Reinforcing Details
Foundation Reinforcing Details
(OP)
I have a concrete foundation supporting concrete column.
Size of foundation is 3000 mm x 3000 mm x 600 mm thick.
There are bottom and top reinforcing for the foundation.
At the vertical face (perimeter) of the foundation, I would put vertical rebars 10M @300 mm spacing with horizontal hook at each end. Also I would put one horizontal 10M bars all around at mid-height.
Reason for this is to prevent concrete cracking/splitting.
Question: Are these extra reinforcing necessary? Is there any code related requirements for this?
Size of foundation is 3000 mm x 3000 mm x 600 mm thick.
There are bottom and top reinforcing for the foundation.
At the vertical face (perimeter) of the foundation, I would put vertical rebars 10M @300 mm spacing with horizontal hook at each end. Also I would put one horizontal 10M bars all around at mid-height.
Reason for this is to prevent concrete cracking/splitting.
Question: Are these extra reinforcing necessary? Is there any code related requirements for this?






RE: Foundation Reinforcing Details
Why is there top reinforcing in the foundation?
RE: Foundation Reinforcing Details
Slick, I've often wondered why so many put top reinforcing in where it seems unnecessary.
I understand that some times it is necessary if the footing has shears and moments that can cause uplift on one side of the footing and thus the soil/overburden wt. causing some tension on the top side of the footing, but I have seen in a lot in footings that I wouldnt think require it.
I admit, I have had a couple very large footings over the years where I put top reinforcing in where it may not have been necessary. I was no where near over-reinforcing it so I just put it in.
I'd love to hear some thoughts from others.
RE: Foundation Reinforcing Details
The question is about the perimeter reinforcing for crack control, is there any code related requirements?
RE: Foundation Reinforcing Details
http://www.nceng.com.au/
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RE: Foundation Reinforcing Details
If I saw a footing detailed the way you described, I'd get my red pen out.
RE: Foundation Reinforcing Details
RE: Foundation Reinforcing Details
As per ACI 318, for relatively deep flexural members(depth, h > 900mm) longitudinal skin reinforcement shall be uniformly distributed along both side faces for a distance of h/2 from the tension face to control cracking in the web. Without skin reinforcing, the width of the cracks may exceed the crack widths at the level of flexural tension reinforcement.
For discussion purposes, let us assume an usual case of a narrow footing of 1200(W) x 3500(L) x 1200mm(D) depth. Unlike pad footings, this footing would behave as a flexural member in one direction only. Now as per the codal requirement, skin reinforcing is required on the longitudinal sides of the footing. A similar condition exists in flexural members like grade beams, strap beams etc., which are more than 900 mm thick. However, skin reinforcing in such situations is generally not provided since the members are buried in the ground. One may exercise caution, though, if the members are below the water table.
RE: Foundation Reinforcing Details
RE: Foundation Reinforcing Details
Would be good to get some more information from the OP.
RE: Foundation Reinforcing Details
RE: Foundation Reinforcing Details
RE: Foundation Reinforcing Details
I have done may jobs where a 10'x10'x2'(~ 7 yards of concrete) footing was the smallest footing on the job. I don't know what industry you work in, but the buildings I design I have had mud mats that took 7 yards.
Call me what you will, but concrete is cheap and foundation upgrades are expensive if not impossible....see my thread on existing footings...http://www.eng-tips.com/viewthread.cfm?qid=315201
RE: Foundation Reinforcing Details
You are right about the cheap cost of "dumped" concrete in pours of 10 to 100 yards because there is minimal forming and little finishing. It does not always fit into the text book estimating costs unless it is a large project where ther are other factors.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.