Concrete Shear wall reinforcement

[Charlie Delta Whiskey]

OK, I have searched and searched and even emailed old professors but I can't find an example of how to calculate the required spacing of rebar in concrete shear walls. Maybe its because it is never a big concern and usually the concrete has sufficient shear strength. I usually dont ever deal with concrete shear walls but sometimes I need to show calcs for an ICF (insulated concrete form) building. So I tried calculating it the same way I would calculate the required shear reinforcement in a concrete beam with a few modifications. Attached are my calcs. Does that look like it could be correct or am I way off? Are there other requirements (minimums/maximum rebar spacing, etc.) for concrete shear walls? What about requirements for special reinforced concrete shear walls? Any help, suggestions, tips, guidance would be greatly appreciated.

Happy Friday everyone!

 

[jayrod12]

Most of what you need is in your local code, i.e. maximum allowable rebar, minimum spacings etc. In terms of determining how much you need, you are on the right path i.e. similar to beam shear, except that in this case it's your horizontal bars that act like your stirrups, and you need to make sure they are anchored appropriately into the end zones where your main flexural steel is location.

Depending on whether your wall is tall and narrow (flexural shear wall) or short and long (squat shear wall)determines how you analyze the wall. Flexural shear walls are designed as vertically cantilevering beams/columns. Squat shear wall generally require strut and tie analysis.

 

[Charlie Delta Whiskey]

Don't both the horizontal and vertical bars provide shear strength. When you make a 45 degree cut you can see that both the vertical rebar and horizontal rebar will be resisting the same amount of tension. Like I said, I could be way off though.

Thanks for your help!

EDIT: OK looking at it again I can totally see that the horizontal bars are the ones resisting the tension from the 45 degree crack and that act like the stirrups.

 

[E720]

If you have Mccormac's "Design of Reinforced Concrete" Book he goes through a good example on this. It is section 18.5 and onward in my tenth edition. I would also give a read on the Earthquake Resistance chapter of ACI 318-14.