×
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

Long Tie-rod Bond Length
2

Long Tie-rod Bond Length

Long Tie-rod Bond Length

(OP)
Looking at the PTI for Rock and Soil Anchors Commentary section C6.7.1-7.2, I read that bond lengths for rock should be limited to 35 ft. While in soil, the limit is 50 ft.  The reason is "inefficiencies".  

The inefficiencies I thought up were in the construction process as result of economic factors.  More powerful machinery. Longer tierods, more grout. Heavier testing equipment.

It mentioned in the case that if such bond lengths are used, "...special provisions are taken to to transfer the load throughout the bond zone".  What provisions?  Is having a longer bond zone the only design inefficiency?  

 

RE: Long Tie-rod Bond Length

It's not economic ineffeciency, it's inefficiency in the load transfer that this suggestion is referring to.  This is discussed in PTI as well as FHWA Geotechnical Engineering Circular #4.  I quote Circular #4:

"For anchor bond zones that function in tension, initial load increments transferred to the anchor bond zone are resisted by the soil near the top of the anchor bond zone as strains occur in the upper grout body (figure 36). As additional increments of load are transferred to the anchor bond zone, the strains in the top of the anchor bond zone may exceed the peak strain for strain sensitive soils. In that case, the bond stress begins to decrease at the top and the peak strain shifts down the anchor body."

Basically you have diminishing returns because the relationship between bond length and anchor capacity is not strictly linear.  AS far as special provisions, one might be to use an SBMA (single borehole multiple anchor) which staggers the free lengths of a multistrand tendon and changes the bond stress characteristics of an anchor in tension.

RE: Long Tie-rod Bond Length

(OP)
Born2drill,

You have two usernames on here? ponder

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