External Tendons on Curved Bridges 1

[otep_imported]

Hello Guys,

I just want your opinion about putting external tendons in horizontally curved box girder bridges. Is it feasible? The external tendons are straight in elevation. I think it may require many deviator. Will it be difficult to do in construction?. Can you please tell me the possible disadvantages of this?

Thank you very much

 

[BAretired]

A curved tendon in a curved bridge acts exactly the same as a straight tendon in a straight bridge. Spaced equally across the bridge, the tendons would produce uniform axial compression along the curve.

BA

 

[LittleInch]

Why don't you draw or sketch what you mean and why you think this is an issue?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Ingenuity]

A curved tendon in a curved bridge acts exactly the same as a straight tendon in a straight bridge. Spaced equally across the bridge, the tendons would produce uniform axial compression along the curve.

BA: I agree if the tendon were INTERNAL, however, the OP stated the tendon are EXTERNAL of the box section.

otep: What if the magnitude of the horizontal curve radius? Why are the tendons straight in elevation?

 

[BAretired]

It would be bad enough putting tendons on the convex face but it would be real fun putting them on the concave face. Maybe otep wants to put them on the top and bottom surface with "deviators" closely spaced to keep the tendons in the desired configuration.

Perhaps a sketch would be helpful.

BA

 

[otep_imported]

Thank you guys for your response!

Here are the drawings.

We already provided internal tendons but it seems that it is not enough to pass the stresses that's why my boss is thinking of adding external. I just want to know the problems that we may encounter when we pursue adding external than adding additional internal tendons. Almost all of the spans are curved in plan.

Thank you again!

 

[pikku14]

It's really dependent on the radius of your curve,where your deviators are and how much prestress you require, whether you have the space to anchor in each span or need to provide continuity across the pier segments. There'll be a horizontal component of the force to consider in the design, but it's not impossible to deal with

Having them profiled vertically as well would be more efficient than seemingly trying to rely mostly on P/A (although that group as shown will still likely have some eccentricity)

Other considerations: what is the construction method? (balanced cantilever span by span etc), do you have room to fit internal tendons in the top or bottom?, do you have room for blisters with your current arrangement without creating sharp curves in the tendons?

 

[LittleInch]

I think it would look rather strange and clearly be subject to corrosion risk plus, especially on the outer curve, how do you extend the anchor section out. The section looks like it is designed to resist vertical load, not horizontal.

If you look up repairs to Hammersmith Flyover in London they have dome something fairly similar to repair some 40 year old internal tendons which have rusted away and built and external set of tendons above and below the carriageway ( down the central reservation), but this was for a straight but vertically curved set of section, though some parts were curved. They also fitted some under the structure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.