×
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

Is there a "BUST" in Appendix D of ACI 318-08 ???
2

Is there a "BUST" in Appendix D of ACI 318-08 ???

Is there a "BUST" in Appendix D of ACI 318-08 ???

(OP)
Something doesn't add up in section D.5.2 (concrete breakout strength). If I work through the example shown in Figure RD.5.2.3, I actually get a HIGHER capaciy using the hef restriction in section D.5.2.3. Here's what I'm coming up with:

Using limit on hef:
hef = 4 in
ANC = 200 in2
ANCO = 144 in2
Nb = 12.1 kips
psied,N = 0.90
other psi factors = 1
----------------
Ncb = 15.1 kips


Neglecting limit on hef:
hef = 5.5 in
ANC = 223 in2
ANCO = 272 in2
Nb = 19.6 kips
psied,N = 0.85
other psi factors = 1
----------------
Ncb = 13.7 kips

The commentary says that the limit on hef is because the results are too conservative using the full embedment. The above example seems to indicate the opposite. The only thing I can think of is that the new hef should not be used in D-6 (even though the code says that equation is included). Am I missing something here, or is there a "BUST" in the code???

RE: Is there a "BUST" in Appendix D of ACI 318-08 ???

Since the commentary is telling you that the full embed depth was too conservative, then you'd expect higher results with the alternate embed depth. The results are consistent with the commentary.

RE: Is there a "BUST" in Appendix D of ACI 318-08 ???

@Frv, I think you misread OP.

@esenef74, The problem with your analysis is that you supposed that an anchor group can be less effective that a single bolt... That make no sense !

Thus, limiting the depth.

Explanation : By increasing hef, you area ratio is going from 1.39 to 0.82... From Amplification due to anchor group to reduction due to edges effect

With 3 edge condition the area ratio because very sensitive and can lead to either result (conservative or not), thus limiting the depth.

Because the area ration is less than 1.0 means that your anchor group is going to be less effective to less than a single rod.

It's like cheating equation by generating higher Anc with a bolt group but getting something less effective that a single anchor rod. That make no sense !

I would like to have others opinion on that... that a good findind !

RE: Is there a "BUST" in Appendix D of ACI 318-08 ???

PicoStruct.. How so? The op mentioned that he thought there was an error in the equation because he got a higher result with a shallower embedment depth. I pointed out that the commentary actually reflects this. Not sure how I misread that.

RE: Is there a "BUST" in Appendix D of ACI 318-08 ???

The whole appendix is a bust.

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