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

Cable stayed bridge in construction stage

Cable stayed bridge in construction stage

Cable stayed bridge in construction stage

Hi all,

I am working on the conceptual design of a cable stayed bridge. The bridge is a composite ladder deck supported by main cable stays which are attached to a curved (anti-funicular shaped) pylon. Each pylon (two at each end of the bridge) is supported by a single back-stay which connects to the edge beams of the deck in the back-span.

During the 'bare steel' phase of the construction i.e. SW of steel, SW of wet concrete and nominal construction load, there is a large compressive force induced in the edge beams of the back span due to the back-stay cable. In its bare steel form, the edge beams are shortening, which is causing loss of tension in the back-stay cable. The loss of tension causes deflection at the tip of the pylon...which causes loss of tension in some of the main stays, resulting in large deflections in the main-span. Evidently I can pre-tension the back-stay cables further to control the pylon tip deflection but this will increase the compression force in the back-span edge beams....which I've found doesn't help my situation.

My question is, would it be common practice to have an additional temporary back-stay cable anchorage to reduce the compression forces directly into the 'bare steel' phase of the back-span? Something like a large counter-weight? Once the concrete of the back and main span decks is cast and cured, the axial stiffness of the deck increases hugely and then the full compression force could be transferred into the deck permanently without experiencing such shortening.

Any feedback or ideas would be greatly appreciated.


RE: Cable stayed bridge in construction stage

In a broad sense, yes, that's one common solution.

As I believe you understand, it's quite a complex problem. Cable stayed bridges are definitely a case where getting a specialized construction/erection engineering consultant's feedback, even in the conceptual phase, is money well spent. Someone like McNary Bergeron or Finley.

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