×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Longitudinal reinforcement on retaining wall footing or foundation

Longitudinal reinforcement on retaining wall footing or foundation

Longitudinal reinforcement on retaining wall footing or foundation

(OP)
All of the examples I have for retaining wall design never show any calc on longitudinal rebars in the footing.  My supervisor always tell me to put #5 @ 12  or close to 12" for foundation wall.  What do you guys usually do?  What do you check usually on longit. rebars?

Never, but never question engineer's judgement

RE: Longitudinal reinforcement on retaining wall footing or foundation

Just check it for Temperature and Shrinkage.  

RE: Longitudinal reinforcement on retaining wall footing or foundation

(OP)
shrinkage for the footing crossection only right?  Thats what I thought too but I have been doing what the boss told me.  I ll tell him.

Never, but never question engineer's judgement

RE: Longitudinal reinforcement on retaining wall footing or foundation

Yes, just T & S for the foting.  I guess if you wanted to check the footing to span over a soft spot in the soil you could, but I can't see any reason to do that, unless you know of a problem (maybe they excavated under the footing and didn't grout it solid).  Either way, that would be a construction issue, not a new design issue.

RE: Longitudinal reinforcement on retaining wall footing or foundation

(OP)
How about the transverse top reinforcement  on the footing (for heel reinforcement), is there a limit on the spacing from ACI?

Never, but never question engineer's judgement

RE: Longitudinal reinforcement on retaining wall footing or foundation

I would follow the spacing limitations for slabs - 3h or 18", whichever is less.

RE: Longitudinal reinforcement on retaining wall footing or foundation

I usually provide the T&S based on the footing section with spacing limits similar to what StructuralEIT says above.  I also usually provide a couple of #4 or #5 bars at the hooked bar as well, just so they have something to tie it to.

RE: Longitudinal reinforcement on retaining wall footing or foundation

(OP)
Another question, does my transverse reinforcement need to exceed T&S (.0018xAg)?  Or can I just use the As I got for flexural?

Never, but never question engineer's judgement

RE: Longitudinal reinforcement on retaining wall footing or foundation

If you have tension, you can't use less than T&S steel.  You can use T&S, but not less.

RE: Longitudinal reinforcement on retaining wall footing or foundation

In reality, the longitudinal bars in a retaining wall footing are not really necessary except to support the main reinforcement and to serve as distribution steel.  Providing the code required amount of T&S steel is appropriate, if that gives you enough support for the main bars.

The place where more bars can do some good is in the bottom of the wall, because the wall is restrained by the footing and will tend to crack at about 10 ft centers.

RE: Longitudinal reinforcement on retaining wall footing or foundation

BULL! hokie66 that longitudinal bars are not necessary... minimum reinforcing is 0.0018 x Ag. The only other thing you can do is design the footing as plain concrete (ACI 318, Chapter 22), but how would you determine bending moments in the longitudinal direction to check concrete stress?

Treating a continuous wall footing as plain concrete for transverse bending, however, is common, if it's not a cantilevered wall. This usually results in a thicker footing, but it's better than having to put 0.0018 x Ag transverse. Also keep in mind that reinforcing, to do the most good, needs to be fully developed. Often, continuous footings are not wide enough to fully develop the transverse bars.

RE: Longitudinal reinforcement on retaining wall footing or foundation

In the longitudinal direction, a reinforced retaining wall is normally much stronger than the footing in bending, so the footing doesn't need to be reinforced in that direction.  Many concrete basement walls are built on unreinforced footings.

In a cantilevered retaining wall, I didn't object to the use of .18% steel in the longitudinal direction, although providing adequate support bars for the main bars in some cases can require more than this amount.  The OP's supervisor who uses #5 @ 12 sounds like me.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources