Reinforced Masonry Wall Question

[DKS71]

Gentlemen,

I am studying for the PE Exam using the NCEES Structural I sample question book. The question I am having trouble with is as follows:
Determine the maximum allowable moment on the masonry wall based on the maximum allowable steel flexural stress.

The wall is 8" block with #5's @ 24" o.c.

This should be just M = As*Fs*j*d
For some reason the solution calculates M (allow) using an As of 0.31/2. Is there a reason to only allow for half the area of steel?

There have been 19 pages of errata for this study guide so I guess my confidence is low in some of the accuracy.

Thank you in advance for any help.

 

[EIT12]

I am also studying for the PE exam, Str II. The examples in the NCEES Structural II had some errors as well.

To answer your questions, the reason As is 0.31/2 is because the given wall reinforcing are #5 at 24" oc.
I hope this helps.

FSAZ

 

[SpecialEddie]

I'm not familiar with the text you are referencing and have not seen the full sample problem, but I am guessing that they are dividing by 2 feet because the bars are at 24 inches on center. This will give you a solution in Area of Steel (or Moment Capacity, depending on how you are looking at it) PER FOOT, which is typically how moment capacity and steel area is calculated.

 

[DKS71]

Thanks guys, you are totally correct. I think I should go for a walk now.

 

[SLTA]

DKS71, good luck. I'm right there with you and desperately need a walk, too. And a vacation when it's all over!