Contact US

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!

*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

In-place Prestressed Concrete Beam Repair

In-place Prestressed Concrete Beam Repair

In-place Prestressed Concrete Beam Repair

Hello all,

I am working on a small bridge rehab project involving some deterioration on the undersides of some members of a adjacent box girder bridge.  It spans over a tidal creek, and removal of the beams is not an option.  The undersides of some of the beams show minor spall, however in 2 places, the bottom shear reinforcement is exposed.  According to existing bridge plans, the prestressed strands appear to rest directly on the topside  of the stirrups.  I need to come up with a repair detail.  My thoughts are that it would be better to not require exposing a large percentage of the stirrups (as typically required for a concrete repair) rather than risk exposing the prestressed strands.  Any thoughts or suggestions??

Thanks alot,

RE: In-place Prestressed Concrete Beam Repair

     Manufacture forms to match the shape of the beams, (paper or plywood works best).  Chip away all loose concrete and steel brush any visible rust from steel at repair site.  Coat with epoxy mix and wait until initial set. Position forms in place with threaded openings and relief tube.  Pump epoxy concrete mix into form until visible epoxy at relief tube.  After epoxy has set, (45 minutes to an hour with warm temperatures), remove forms and grind imperfections smooth. Trowel on cement based coating to match color or paint to match.

RE: In-place Prestressed Concrete Beam Repair

Verify that you have not lost a lot of PS steel cross section due to corrosion. Spalling could be from the PS steel also. A 0.1% loss on reinforcing steel (maybe an approx loss of 6ksi) is not the same as a 0.1% loss on PS steel (approx loss could be 25ksi).

RE: In-place Prestressed Concrete Beam Repair

As a Bridge Contractor, in 1977, we had a job virtually identical to what you have described. The repair technique specified was virtually identical to what civilperson has recommended. After repairs, the bridge stayed in service for another 20 years (without problems) and was finally replaced because of functional obsolescence - not structural deficiency. Suggest serious consideration of civilperson's advice.

www.SlideRuleEra.net idea

RE: In-place Prestressed Concrete Beam Repair

     A ten per cent loss in cross sectional area would give a decrease of tensile strength in grade 60 rebar of 6 ksi x original area, and a similar ten per cent loss in prestressed strands area would decrease the strength 25-27 ksi x original area.  (Probably a typo.)

RE: In-place Prestressed Concrete Beam Repair

Thanks, civilperson. That is exactly what I meant.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close