×
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

Bridge design

Bridge design

Bridge design

(OP)
What is the maximum length one might consider using beyond the center line of bearing on a plate girder bridge?  I am concerned about the uplift at the end.

RE: Bridge design

Maximum span length? or Maximum length from the very end of the girder to the centerline bearing?

If it's the latter, this distance is typically controlled by the equivalent column section formed by the web and stiffeners.  AASHTO has precribed amount that may be considered for the effective column web distance.  

Obviously such distance would be no more than absolutely necessary.

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

RE: Bridge design

Sorry Bridgemann, uplift? I find your post confusing. Could you please clarify?

To add to what Qshake said, there might be a minimum distance beyond support stiffener by code if working on seismic region. It is supposed to prevent unseating of the span in the case of earthquake.

Also it will depend on what kind of bearing you have.

RE: Bridge design

Is this about the slope of the girder over the support?

Michael.
Timing has a lot to do with the outcome of a rain dance.

RE: Bridge design

Continuous span bridges with a short span next to a much longer span usually result in an upward reaction.  One way to get around this is try to make your spans closer to the same length or you can always provide a stopper so that the girder can't move upwards at the bearing.  I've seen numerous situations like this for rehab jobs.

RE: Bridge design

Are you asking about the maximum length the end of the girder should extend beyond the centerline of bearings?  I don't know that there is a maximum allowable.  I think you would need to determine what length you need and see if it's doable.  Will there be too much vertical offset at your joint?  Will the negative moment over the support be too great?

RE: Bridge design

(OP)
Sorry for the confusion.  This is a bridge rehab project and the cl of bearing of the girders at the abutment is not parallel to the the backwall.  The girders extend to 3 1/2" of the backwall to support the deck slab.  The distance from the centerline of the bearing on each girder to the end of the girder varies from 6" to as much as 2'.  I am concerned about the uplift that would occur with that 2' cantilever.  The bridge is on a curve and on a skew.  The maximum extenstion beyond the cl of bearing is in the obtuse corner side of the bridge.     

RE: Bridge design

I see.

Why don't you do a deflection check? It should be relatively simple and it will tell you if you really have a problem or not. Chances are that the deflection up will not be more than a couple of mm.  

RE: Bridge design

Two feet from *centerline* of bearing to the very tip of the girder seems pretty normal to me.  You're just talking a few hundred pounds of steel; I don't think the bridge would notice.

Hg

Eng-Tips policies:  FAQ731-376: Eng-Tips.com Forum Policies

RE: Bridge design

If you have a problem with upward deflection at the end of the girder (24"x slope at support) you will have a much bigger problem with center span deflection. Two feet is not unusual.

Michael.
Timing has a lot to do with the outcome of a rain dance.

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