If I have a CMU column experiencing a small amount of wind overturning, does the footing need top reinforcement? 3

[reverbz]

Basically the title but do I need top reinforcement in this scenario in the footing? I thought it creates tension in the top of the footing but another engineer is telling me I don't need it so I'm just trying to undestand


thank you!

 

[Ron247]

Are you saying there is a small applied overturning force or a net overturning force? If the top is not in tension, then bars may not be needed. You need to better depict your concern.

 

[XR250]

Check it as plain concrete.

 

[JAE]

The downward force in the column will produce "positive" bending in the footing, requiring bottom steel.
However, any load combinations that produce lateral overturning moment at the base of the column will produce positive moment in the bottom of the footing on the leeward side and negative moment in the footing on the windward side.

If the negative moment exceeds the gravity positive moment then there's net tension in the top (as Ron247 suggests) and you will need top steel.

You need to check your footing under all the required load combinations to see if this is the case.

 

[BAretired]

You are not wrong. An overturning moment puts tension at the top of the footing. If the compression from dead load exceeds tension from wind moment, then theoretically, reinforcement is not required; however it may be prudent to provide minimal top bars if there is any doubt.

 

[Ron247]

If the conditions/loading exists that puts the top of the footing on "the outside of the curve', then there is tension. There can be magnitudes that don't result in tension on the top face.

You can get tension in the top from just uplift without overturning if uplift exceeds gravity loads and therefore FOSuplift <1, so your load magnitudes are more important than a scenario without load magnitudes.