×
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

AASHTO Rock Socket Side Resistance

AASHTO Rock Socket Side Resistance

AASHTO Rock Socket Side Resistance

(OP)
The formula given in Article 4.6.5.3.1 of AASHTO HB-17 (page 85) for ultimate side resistance reads as follows:

Qsr = (pi)*Br*Dr*(0.144*qsr)

Yet the label on the y-axis for Figure 4.6.5.3.1A indicates that qsr is the unit side resistance.

Should the formula read:

Qsr = (pi)*Br*Dr*(144*qsr)

to make the units work out?! Or do they intend to reduce Qsr by a factor of 1000 for some reason?!

All responses welcome.

Note: Originally posted in AASHTO Code Forum.

Jeff

Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com

RE: AASHTO Rock Socket Side Resistance

I think the equation is correct. qsr is in psi (lb/in^2), but the other units are in kips or feet.  So the conversion factor of 0.144 is equal to

(12 in/ft)^2
---------------
1000 lb/kip

The notation and the units for each symbol can be found in Sectino 4.6.2 on page 79.

RE: AASHTO Rock Socket Side Resistance

(OP)
Panars,

Thanks for the explanation. I had not considered that the units of Qsr would be specified.

Jeff

Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com

RE: AASHTO Rock Socket Side Resistance

jdonville,

I posted the thread "DS Uplift Capacity with Socket". Does the AASHTO HB-17 publication address total side resistance (soil resistance + socket resistance) and the resistance distribution along the shaft? I'm looking at uplift capacity from soil and socket contribution.

Is the publication available on-line?

Jefferys

RE: AASHTO Rock Socket Side Resistance

(OP)
jefferys,

HB-17 is the AASHTO Standard Specifications for Highway Bridges, 17th Edition (2002). It is most definitely not free (unfortunately)! Copies are available from AASHTO (www.aashto.org). However, Amazon.com and ebay might have 3rd-party (used) copies available. Note that this version will be officially deprecated for highway structure design in a year or two when the LRFD version will be the "official" design basis for federally-funded projects (and likely many state projects, too).

Unfortunately, the document does not give any specific guidance on this topic - which I am pained to admit that I don't know as much about as I should. I am currently looking at DSs with rock sockets for a current project, but they are fortunately short (<15 ft OA) and I will assume negligible contribution from the soil for skin friction.

Off the top of my head, I don't know of any source giving explicit design guidance. But please do let us all know if you find some.

Jeff

Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com

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