Jointless Bridges

[cancmm]

I'm looking at designing a 50' single-span filled-spandrel arched bridge. The bridge will be constructed entirely of concrete and filled with soil. Abutments will be cast against rock. An example can be shown here:

http://www.fhwa.dot.gov/nediv/bridges/unname1.jpg

It would be very easy to construct the arch slab and walls integrally with the abutment, but I'm concerned about thermal stresses without any expansion joints. The bridge will be located in a tropical/humid climate and above water, so I think that AASHTO recommendations are too conservative. However, in modeling the arch with fixed supports under temperature change in accordance with AASHTO, the results are extreme. This concerns me and makes me hesitant to simply discount the load.

I know that Tennessee uses jointless bridges a lot, but I can't find any solid guidance on the issue. Any thoughts on how I should tackle this?

 

[cvg]

looks like a con-arch / con-span bridge, no need to re-invent the wheel

http://www.con-arch.com/home.html

http://www.con-span.com/con-span/main.html

 

[cancmm]

Looked into this already. Unfortunately the site is quite remote and shipping makes it cost-prohibitive.

 

[Qshake]

So the intent is to have the contractor site mix concrete? Assuming, of course, it's so remote that no batch plant is nearby.

Regards,
Qshake

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

 

[cvg]

for con-arch, I believe the only things to be shipped are concrete, rebar and forms - pretty much what you need for any cast in place structure. for con-span - yes, they ship it complete to the site.

 

[cancmm]

Sounds strange I know. It's a remote island job where they set up a small batch operation onsite using premixed bags of cement/aggregate. Import duties and taxes combined with the shipping make conspan cost prohibitive. Trust me we priced both options.

 

[Zambo]

For a remote location site batching the concrete is common and shouldn't provide too many difficulties. It is much better that the mixing is done by weigh batching rather than volume batching.

Not sure why you would have pre-mixed bags of cement/aggregate. I would prefer to keep the cement separate until time to mix the concrete.

It sounds as if the temperature range where you're working is not very high.

 

[tumbleleaves]

I don't think they've been doing them that way since the 1940s. I can only remember specifically one bridge that I inspected that looked like that (1930s), but I have limited experience and never worked as a bridge inspector or for a DOT.

AASHTO recommendations are likely fine, hinterland American bridges are subject to much higher temperature variations; as hot and inhospitable as the tropics may seem it is temperate. Plus the bridge is so short, no problem being integral.

I suppose that you are using an arch so that you can minimize the steel quantity and this is making you worry about temperature cracks.

Good luck.