Retaining Wall - Stem Reinforcement distribution 5

[XinLok]

I am reading one article about desigining a concrete retaining wall.

The As required for Stem is As: 2.26 in² per 1 foot.
Author use #9 each 4.5" (Center to Center)

Why AS is equal to 2.67?

As required is 2.26 in², so he should be using 3 #9 (3 in²)each 1 foot.

Any explanation?

Thanks and Regards

 

[hokie66]

(12/4.5) x 1.0 = 2.6.

But I can't tell you why he didn't use #9 @ 5" = 2.40 in^2, greater than required.

 

[XinLok]

Thank you for your reply.
I am confused how to distribute the reinforcement in the stem.

I draw this to show you how I am distributing the reinforcement:

Is this the correct or not the proper way?

The reinforcement is 2.2 in² per 1 foot, so if I use 2 # 9 per 1 foot, the reinforcement area is just 2 x 1 in² = 2 in².

 

[hokie66]

Yes, what you show is, I think, 2 in^2 per foot. That's because your spacing is 6", not the 4.5" as the author suggested, or 5" per my post.

But this spacing is along the length of the wall, not across the width. Not sure what you are dimensioning as 12".

 

[r13]

Provide 2#10 @ 6" O.C. will eliminate the confusion. As = 2.54 in² > 2.26 in².

OP, try avoid decimal bar spacing, and provide number of bars can be spaced equally in a 12" strip [Bar Space = 12/(#Bars+1) = whole #].

 

[Lomarandil]

Sometimes the bar spacing in one part of a retaining wall is driven by another part -- e.g. the toe or heel. Constructibility improves when the different spacings are multiples of each other.

----
just call me Lo.

 

[PEinc]

Or, a 4.5" spacing works out as the actual bar spacing for the wall section's actual length after you subtract the required rebar cover at each end of the wall section.

http://www.PeirceEngineering.com

 

[XinLok]

Great people.
Thank you all

 

[Ganesh Persaud]

Designing these, we do a 12 inch wide strip. After computing the Area per design strip as required, you could use the attached table to correlate bar size and spacing with its respective areas. The goal is to chose a bar size that’s locally available and Based on your judgement the spacing you want with that 12 inches so that we chose an area a little above the required so that the design satisfy the strength requirements.

See link. Hope this helps.