Finish Grade Elevations For Widening

[Darkangel24]

Hello,

I had to find the FGE's for a existing bridge subject to widening, the bridge is on a curve both Horizontally & Vertically and the bridge is highly skewed. We were able to get survey snap shots over the existing bridge, The survey snaps show that the bridge does not align vertically or horizontally to the design data that was in the concept plans.
So i converted the survey snap shots to 3D file with true elevations and converted it to a Tin file using Geopak in Microstation, merged it with the existing and proposed widening bridge layout, using the existing survey snap shots i extrapolated the available data to get the FGE's for the widening part.
My question did i put myself through too much trouble? is their an easier way to get FGE's for proposed widening and is there any way i can back check what i did?

Any comments on this will be very helpful.

Thank you,

Nikhil

 

[bridgebuster]

Are you taking the deck of of the existing structure or just widening? It makes a difference. Your final elevations are - more or less - whatever you want them to be; it all gets made up in the haunch.I'm working on a deck replacement for a very long structure. It's all being done in stages and it affects the deflections.

TIN, Geopak, 3D all Greek to me. Think about how the structure will behave during construction in order to determine your deflections.

AASHTO/NSBA has a paper out on this subject.

 

[Darkangel24]

The existing bridge will be saw cut at the center line of exterior beam and the proposed surface will extend of this cut line.

 

[bridgebuster]

OK, so now you know the roadway elevation at the cut line, the proposed roadway elevations of the new sections, now it can get a little tricky. You have to figure your deflections so that you get get the road where you want it. Perhaps a 2'-0" closure pour might be something that you should consider.

 

[Darkangel24]

Thanks

 

[bridgebuster]

no problem