×
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

Corbel -reinforcement Af to resist factored moment

Corbel -reinforcement Af to resist factored moment

Corbel -reinforcement Af to resist factored moment

(OP)
So I am calculating corbel reinforcement and I've gone through all the required ACI reinforcement equations ( Avf, An ) and am about to calculate As which is the primary reinforcement. In order to compute As, I need Af which is another reinforcement requirement established to resist factored moment per section 11.8.3.3 ACI-11. this moment is equal to Vu*av + Nuc*(h-d) according to this section. Since the ACI does not have a set formula for Af I had to resort to another book - The PCI Handbook to see if they had one and thank god they did.

They say Af = [ Vu*av + Nuc*(h-d)] ÷ [ Φ fy d ]

BUT I was using a design book as well while I was researching this topic on corbels and they use this equation :

Af = [ Vu*av + Nuc*(h-d)] ÷ [ Φ fy 0.9 d ]


SO now I don't know which book has the right formula. The only reason I can think that they might put 0.9 is because of the flexure theory but even then am I really supposed to put the 0.9 there because according to section 11.8.3.1 the Φ=0.75 for all design calculations in 11.8 of ACI. or maybe I'm interpreting it wrong and it is implied that I'm supposed to use the 0.9 I am unsure. I would love some clarification if anyone knows more about this than me. Thanks!

RE: Corbel -reinforcement Af to resist factored moment

Without knowing what design book you're reading, the 0.9 factor is likely an attempt to calculate the depth of the compression block (the same reason that the moment arm in for typical beam reinforcing is d - a/2). I'm not sure this is really necessary since your concrete will extend past the bottom of the corbel, but it shouldn't have much of an impact on your steel values.

If this is a precast concrete project, your notes/specs likely stipulate that the design will be per the PCI handbook.

Brian C Potter, PE
Simple Supports - Back at it again with the engineering blog.

RE: Corbel -reinforcement Af to resist factored moment

(OP)
Okay yes I was thinking that too. I'll go with the PCI handbook. Thank you

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