Anybody deal with "one U-section-beam bridge"

[flong]

We recently got a bridge and archtect prefer to design a one-beam-bridge Which means the bridge cross-section is a big U-beam supporting deck. There are also some diaphrams inside of u shape beam.
Anybody get an idea which software could design it? Or where I could find useful information regarding this?
Thanks!

 

[mjl23]

What is the span length and what loads are expected (what loads are being carried by the bridge)?
Those answers might give direction if you'll have standard reinforced concrete or prestressed, etc.

 

[Qshake]

Precast U beams are common in Texas and with Nebraska....this is precast. SO you can look to their website to see if you find something useful,

For cast in place, if you place the deck on the u shaped beam all you have is a box beam and I would think you'd know how to deal with that.

As always follow the code and ask a senior engineer when you need help.

Regards,
Qshake

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

 

[flong]

It is under HS20 load, 3 spans, 65' each span.
It is probably post-tensioned beam. and the width of beam is about 50'.
Thanks!

 

[bridgebuster]

It sounds like an upside down JMI Channel bridge. A couple were built in NY in the 90's. They're segmental post-tensioned bridges, although I understand that they can be cast-in-place post-tensioned as well. The post-tensioning ducts would be in the vertical portions of the "U", which will be fairly thick.

See if you can get a copy of "The segmental Concrete Channel Bridge System" prepared by Civil Engineering Research Foundation, Report No. HITEC 96-01.

JMI was a consulting firm that started after Figg & Meuller parted company. JMI no longer exists; it was sold a few years ago.

 

[mjl23]

I'm not sure if the previous answers gave you enough. If not, could you tell me if you or your office is experienced with bridges, I would adjust my response knowing your experience level with bridges.

I don't know that much about segmental bridges, but the span lengths you mention seem small to use conventionally
segmental construction efficiently.

The width stated seems very wide for the 'beam' as well (seems like you'd need some interior webs). What is the roadway width and do you know who the owner would be (meaning is it a state, city, county, or private entity)?

 

[shin25]

I am not sure if your beam is going to be precast. If so, the section will be too heavy to handle and too wide to transport by road.

As far as design, I think 65' span is not too big. For design concept, you probably can check chap-4 of AASHTO LRFD for effective flange width etc. And chapter-3 for load combination and load effects.

 

[flong]

This is a project in Asia. Yes, it may be segmental post-tensioned beam. Width of roadway is 65' which means 2 lanes on both direction.
We are in the preliminary design stage, so some information are not clear enough or not decided yet. We do have a senior engineer experienced similar bridges before but it's many years ago and he doesn't remember most of it.

 

[bridgebuster]

An 8 x 50 segment is not unheard of; it might not be transportable depending on where it's going to be built. Anyway...

flong - I think going segmental might be a waste of money. THursady, when I'm back in the office, I'll check to see what the maximum width for the JMI system was. It was intended for short span bridges but I don't think 50' wide.

You can span 65' with a prestressed voided slab, continuous for live load. Add a deep precast fascia panel, make it look like a "U"
________________________________________
| |_______Voided slabs_______________| |
| | | | Precast fascia
| | | |
--- ---

I've done some precast bridges this, with curved fascia panels. I also know what it's like dealing with architects and some of their dumb ideas.

 

[bridgebuster]

My sketch got messed up it should've looked like this:

_________________________________________________
| |___________________________________________| |
| | | |
| | | |
| | | |
--- ---

I found some information on the JMI Channel bridges, a few were built in NY state in the the 90's. They were about 40' wide; 32-foot roadway; 4-wide ribs; spans were in the 100' range.

 

[mjl23]

I doubt you could get that configuration built in the US. Considering the span vs. width vs. constructibilty I can't see going with a mono box type deal.
I guess you're a sub to the architect or at least secondary to the aesthetics.
You might check into using precast inverted T beams and then do a cast in place deck on top. That may get you a similar look. Otherwise I think typical construction for the US would be to use standard AASHTO prestressed beams.

 

[bridgebuster]

My sketch keeps getting messed up

 

[mjl23]

bridgebuster

Try using [ ] with tt inside, see the TGML markup just below the window you type in.

The window you type in shows courier which keeps text aligned but the posting page does not. If you use tt it should position it properly.

 

[bridgebuster]

Thanks

 

[flong]

Thanks, guys!
Yes, We got the sub from an architect in Washington and the bridge is going to be constructed in Sadi Arabia.
I maybe missleading you guys. We discussed this issue again yesterday and we found some similar bridge details and calculation example from CALTRAN. It is a whole piece Box beam built in Califorlia. They couls span 110' with a 45' wide conventional box beam. The only difference is they used rectangular void instead of circular void as architect suggest.

 

[flong]

We were thinking it is one-piece-U-beam because we thought it is a big U beam with diaphram inside the beam. It does looks like it but we will go with one-piece-box-beam now.