×
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

Stream Force on Bridge Piers and Abutments

Stream Force on Bridge Piers and Abutments

Stream Force on Bridge Piers and Abutments

(OP)
On AASHTO 17th Ed Section 3.18.1.2 the code tells "When the direction of the stream force is other than normal to the exposed suface.....the effects of the directional components of stram flow pressure shall be investigated."
My question is: How do you define expose area, area perpendicular to the flow of the member or area along the member?

RE: Stream Force on Bridge Piers and Abutments

The exposed area of the pier is the width of the pier multiplied by the 100 year depth of flow at that location.

However, I would not forget about the instance of logjambs at the piers during high runoff.  I've seen it happen and often.  That will substantially increase the lateral load to the piers.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Stream Force on Bridge Piers and Abutments

Often the piers will be aligned as best they can to the direction of flow.

RE: Stream Force on Bridge Piers and Abutments

A pier consists of 4 faces - upstream, downstream, and two side faces. The long direction is usually aligned in direction of flow, however, skewed piers happen quite often also. So, other than head-on forces, there is also side pressures. Depending on the usage of the flow channel, you may need to check effects of vessel/log impact, debris and ice loads.  

RE: Stream Force on Bridge Piers and Abutments

Piers are most often skewed to align best with flow, however there many applications where this is not the case.  For example, in a large watershed area that has a small creek but a very large overflow area or valley section.  In the overflow area, stream flow may not be aligned with the creek proper and in extreme cases, flow can be somewhat perpendicular to flow.  Can you align piers to match overflow? Sure but for long bridges and odd stream meander as well as valley direction it's not always possible.  

Regards,
Qshake
pipe
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
 

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