×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Girder Tensile Stress in Precompressed Tensile Zone At Service III?

Girder Tensile Stress in Precompressed Tensile Zone At Service III?

Girder Tensile Stress in Precompressed Tensile Zone At Service III?

(OP)
The WSDOT Bridge Design manual [5.2.1.C] does not allow tension in bridge girders at the service III limit state, i.e. final stresses after losses with all permanent loads plus live load. AASHTO LRFD 9th edition Table [T5.9.2.3.2b-1] allows some tension in the precompressed tensile zone assuming uncracked sections.

I am typically designing with the 0.19λ(f'c)0.5=0.19(1)(8.5)0.5 = 554PSI < 600 PSI limit for not worse than moderate corrosion conditions. The majority of the designs I have been involved in both classical prestressed girders and post-tensioned structures result in some tension during Service III with live loads.

WSDOT BDM says "The tensile stress in the precompressed tensile zone for the final service load condition (Service III) is limited to zero. This prevents cracking of the concrete during the service life of the structure and provides additional stress and strength capacity for overloads."

  • What are your thoughts?
  • Does your DOT have a provision similar to WSDOT or do you hold you design to zero tension at the bottom of your section during Service III? (with live load)
  • Do you think the zero limit is necessary to control cracking since this is more restrictive than AASHTO? Or is it potentially overly conservative?

RE: Girder Tensile Stress in Precompressed Tensile Zone At Service III?

It seems to me that WSDOT is acknowledging that their restriction is more conservative, and that's the way they want it.

RE: Girder Tensile Stress in Precompressed Tensile Zone At Service III?

(OP)
I must have found this topic more interesting than the other bridge engineers around here.

What intrigues me the most is that limiting designers to ZERO tensile stress at SERVICE III would often result in deeper girders, additional girders lines, and an increased prestressing steel quantity within girders. All of these things increase project cost and ultimately cost tax payers more dollars. Engineers are stewards of tax payer dollars and I'm not convinced this practice ultimately benefits the structure's performance or service life. It'll be interesting to see over time if more states adopt this practice, if AASHTO adopts more stringent criteria, or if we can tell structures designed in this manner actually benefit in a meaningful way.

RE: Girder Tensile Stress in Precompressed Tensile Zone At Service III?

Perhaps WA doesn't want its bridges falling down in earthquakes, hence the conservatism.

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


Resources

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