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RE: CONCRETE Wall Shear question

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Commentary Section R21.6.4 to ACI 318-99 states that Eq. (21-7) (which is the same as in the 1997 UBC) recognizes the higher shear strengths of walls with high shear-to-moment ratios. It also gives 3 good references which describe, among other things, some tests that were done that led to this equation. One important thing to keep in mind when comparing the shear equations in Chapter 11 and Chapter 21 is that you should compare design strengths (phi x Vn) and not nominal strengths (Vn). For walls with a height to length ratio less than 2, which you have in your case, the strength reduction factor will most likely be 0.60 and not 0.85 (see ACI Section 9.3.4 or UBC 1909.3.4.1). For walls with a height to length ratio greater than or equal to 2, phi will most likely be 0.85.

Dave Fanella

David A. Fanella, Ph.D., S.E., P.E.
Director of Engineering
S.K. Ghosh Associates, Inc.
1856 Walters Avenue, Suite 200
Northbrook, IL 60062
Ph: 847.291.9864
Fax: 847.291.9865
E-mail: dfanella(--nospam--at)
Web Page: 

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