Foundation reinforecment

[aladdin76]

house with spread footings, I wanted to use U shaped reinforcement for the footing, the contractor wanted to use straight reinforcement, would any one please let me know if there is any standard specification that require u shaped steel,, BS or ACI , just refer to the number of the spec.

 

[hokie66]

This is controlled by the development requirements for the reinforcement. If you showed cogs on the bars, the contractor should do what he bid on.

 

[ishvaaag]

I remember a head of the department of structures of the ETSAM (and not a bad one, I can attest, since was a professor of mine doing extremely intelligent structural charting works in the seventies') stating at some conference to colleagues quite hilariously, please do not buy the new RC code, and also laughing at the bent details at footings. He was saying that for ordinary buildings with ordinary practice here many of the clauses mean scarce thing. One can go to such skeptical view after decades of sound practice, yet for the unaware can be a worrying risk.

In any case, if allowed by your code, you can weld the straight mesh to reinforce the footing and then you have the tips themselves anchored through shear-friction effect, since there the required steel stresses are minimal and the transverse sections and tributary adherence surfaces are more than enough.

 

[rtmote]

How deep is the foundation? And how wide? If the footing is big enough, you won't need any bars! The bottom mat/bars will help to prevent the bottom face being split into tension by the applied load. So if there is enough development length of bar outside your 45 degree cone then fine otherwise if your footing is more compact you will need more length and bend up the bars. No code will stipulate u-bars, only the requriement for anchorage outside the zone of loading.

Ishvaag, he sounds like someone who had a lot of wisdom! People forget we have been building refineries for a hundred years before codes popped up. And the next new requirement really worries some!

Robert Mote

http://www.motagg.com

 

[StructTaco]

Typically the bars are not bent up, look at the unreinforced concrete provisions in ACI 318, you'd be surprised that you may not even need steel. Most spread footings are shear controlled until really big.

 

[msquared48]

Unless you have a grade beam critical in shear (vertical orientation), I see no reason for "U" shaped bars, especially laying it flat. Usually the bars are straight in the bottom of spread footings. Cutting once and bending once is a lot more labor than cutting twice. You are also wasting steel in the length of the bend with nothing gained.

Mike McCann
MMC Engineering