Designing special reinforced concrete shear walls

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I am designing special reinforced concrete shear walls which has two openings at the lower half (see fig). Sections R18.10.1 directs me to design part 1,2, and 3 as the wall pier which is similar to column as in special moment frames. For calculating the design force for shear strength (18.7.6.1), I do not understood how to calculate Ve. Can anyone help me answering my following questions?
1) Mpr for columns at each end will be same given that the same reinforcement is present at the top and bottom of column, isn't it?
2) How Pu is related to the Mpr values?
3) We will not have beams in this case. So check for Mpr of beams is excluded right?
4) Ve shall not be less that factored shear calculated by analysis. What does this actually means?
Can some one explain this in simple terms? If there is any reference calculations please share. Thanks.

 

[sticksandtriangles]

By no means an expert on this, but I will throw some answers in here to hopefully start the discussion and improve my own understanding.

1) Mpr for columns at each end will be same given that the same reinforcement is present at the top and bottom of column, isn't it?
- Yes I believe so, if they have all the same reinforcing/concrete and axial loads (see below)

2) How Pu is related to the Mpr values?
- You should be making a PM interaction diagram, in general, as you increase axial load (compression), your Mpr goes up.

-One oddity I see in your image, it looks like your are analyzing your wall pier for out of plane moment? Is that right?
-One area that I do not know standard practice on, do engineers do a worst case axial tension load and a worst case axial compression load for their seismic designs? Seems like differing Pu values could affect Mpr and the corresponding Ve? It might be the axial compression always controls the design, as you will get higher Mpr values with higher axial loads.

3) We will not have beams in this case. So check for Mpr of beams is excluded right?
- That's right, here's how I would do capacity based Ve determination

4) Ve shall not be less that factored shear calculated by analysis. What does this actually means?
Im a little unclear on this, but I think Ve needs to be the maximum of either the capacity based Ve shown above in my sketch or the factored up elastic Vu force. Which ever is greater is what you design the wall pier for. Essentially, you want to ensure the wall fails in flexural yielding before shear failure occurs.

 

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Great help! Thank you. Yes, the figure there was for out of plane shear. I just wanted to look at out of plane shear but i am more concerned at in plane shear. How do you generate P-Mpr diagram? Did you include 1.25Fy factor for steel? Which software are you using? Can you please explain it a bit more?

 

[sticksandtriangles]

To generate a P-Mpr diagram, yes 1.25 is generally the play. ACI snip

Other than that, a P-Mpr diagram is pretty much the same generation process as another PM diagram generation. Pick a few neutral axis depths, solve for M and P.

There are a few tools out on the market that will generate P-M diagrams for you. The one I showed is on my website, but is not suited for real design at this point. It is hard coded for 4ksi concrete and 60ksi steel. DO NOT USE IT TO DETERMINE Mpr

S&T -

http://www.re-tug.com