Retaining Wall Dowel Embedment / Development length

[bridgeengineer2007]

When determining the length of a dowel in a retaining wall, it appears the dowel will be in tension due to the lateral force of soil. Per ACI 12.2.2, the development length for a bar in tension results in 59" for an epoxy coated #6 bar with 3000psi concrete! Am I missing something? From other state standards for a straight development length, a #6 bar should be along the lines of 15" or so.

I feel like I am missing a reference to dowel delevopment. Please help.

 

[ztengguy]

what equation from 12.2 you using, and what factors for said equation? seems epoxy should be 1.5 or 1.2 (whats your spacing?) and together factors not to exceed 1.7

Since you are vertical, and I would think your spacing is greater than 4.5", your factors would be 1.0, and 1.2 giving you a length of 42"

Also you can apply excess reinforcing equation too, that would reduce if you dont need full #6 at said spacing.

Im not sure if you think 15" is acceptable, but min length I get from 12.2.2 is 33"

 

[dcarr82775]

58" is longer than I would get for most any circumstance, but 15" is way to low.

 

[bridgeengineer2007]

I have a #6 bar (assumed in tension), epoxy coated, grade 60 steel, clear spacing and cover are both greater than the limits.

ld = ( 3*60000*1.2*1.0*1.0*0.75 ) / ( 50 * sqrt(3000) ) = 59"

 

[delagina]

use 12.2.3

 

[cap4000]

Can you use the other formula in the chart. Also take a look at 12.2.5 for a possible reduction.

 

[dhoward26]

There could be different answers to what you are posting your questions about:

1) Are you asking for Dowel Embedment/Development Length from the wall into the footing?
2) Are you asking for Development length in the wall itself with bars lapping?

 

[slickdeals]

Not a big fan of epoxy coated bars.......a little nick and there's a corrosion hotspot.

Recently, I was watching a bridge project Bandra-Worli Sealink on the Discovery Channel and they were proudly saying that the reinforcing bars are epoxy coated for long life, but a close up shot of the rebar cage showed regular tie wires (some with rust). Go figure!

 

[ztengguy]

why not use the (fy/25 Sqrt F'c)*db

((60000*1.0*1.2)/(25*sqrt3000))*0.75 = 39.4", then the provisions of 12.2.5 as well.

Perhaps I am missing something too.

 

[cap4000]

Check out Table 6 in the link.

https://engineering.purdue.edu/~fro...gths of Reinforcing Bars under ACI 318-08.pdf

 

[ztengguy]

BTW, I am looking at ACI318-08, so not sure what you are using.

 

[bridgeengineer2007]

Thank you everyone for the help - I believe the huge difference from my initial calcs were due to using 12.2.2 and comparing to MD State Standards which were developed using AASHTO LRFD. AASHTO does not have separate criteria for #6 bars and smaller. All of these together probably makes up the difference.

-Much appreciated