Bridge Rehab - Integrating bridge decks

[Quanski]

I am working on a bridge rehab project; the existing structure consists of two span steel plate girders complete with a concrete deck simply supported on concrete abutments and a centre pier. The key tasks are to convert the existing deck to a semi-integral configuration over the abutments as well as integrating (making continuous) the decks over the pier to eliminate the joint. To achieve this, a section of the deck over the pier will be removed and replaced c/w the required reinforcing to resist the new negative moment over the pier. I am looking for recommendation/guidance on how to treat the girder ends at the pier. I imagine field splicing will be required to make the girders continuous as well. What is typically done? Bolted or welded field splice? If bolted, how are bearing stiffeners incorporated. Can anyone provide an example of structural details for a similar situation? Thanks for your help.

 

[Qshake]

The simple span steel made continuous has been done before and I believe you can find details of this in the NYDOT manual. Otherwise you might want to look through IDOT's Structural Services Manual.

I do not know of any design example that exist for the procedure.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[Quanski]

Any idea what section I have to look in?

 

[Qshake]

No, not really. You can check this link out for a published paper on the work and a reference to NYDOT. Also NCHRP lists Roland Berger as doing some research in this area so you may want to google him and the subject matter.

http://best.umd.edu/publications/report02.pdf

Good Luck.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[bridgebuster]

Download the NYSDOT Bridge Manual here:

https://www.dot.ny.gov/divisions/engineering/structures/manuals

go to Chapter 19. The detail you're looking for is on Page 500.

 

[huntley101888]

Excellent response, bridgebuster. I'd also like to add that you need to analyze the beam to make sure it can handle the different stress configurations that it will see when it is made continuous. Like you said, Quanski, there will be negative moment at the pier now, and that's something that the original beam wasn't designed for.

 

[wiktor]

I think Bridgebuster covered most of it, but I will add some:
1.Re-design the bridge as continuous for live load moment only. This will reduce the work required, as slicing of the webs could be omitted.
2.Existing bearings could be left in place with possible blocking, if you were converting the bridge into jointless structure. Current configuration is 0-0-X or 0-X-0, after conversion it could be X-X-X.
3.Continuity plates or angles will be needed at top and bottom. Top shall be bolted; bottom could be welded in form of kick plates in between bottom flanges. In the design carry all LL negative moment via steel plates, do not count on the deck reinforcement.
4.Consider local post-tensioning in form of HS bolts installed below the top flanges. This may eliminate or reduce otherwise unavoidable transverse cracking of the deck. Other more fancy technique could be lifting the girders at the center pier prior to casting new deck, and lowering it after hardening of the concrete. This will post-tension the deck in the LL negative moment zone.
5.Provide strain relief joints in the new deck. This is typically done in a form of cut in the hardened deck, ¼”x1” filled with elastomeric filler and placed at the center and at ½ of negative moment envelope reach.
Regards
Wiktor