Suggestions for design of bridge spanning thirteen meters? 1

[diesto]

Hi! I'm supposed to design a bridge that spans 13 meters only and has a carriage width of about 9 meters. The problem is that a cement mixer weighing 30 tons has to pass through it.

I've already tried slab bridge with ACI specifications and a box culvert. Both resulted in a very thick bridge deck and high strength concrete. My superior asked me to explore other options. Does anyone have any other suggestions. Thanks!

 

[ACtrafficengr]

What's passing over it?

If the concrete truck is going through it, you obviously don't have to worry about scour. You might be able to save money with GRS wall abutments:

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/11027/index.cfm

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/11026/index.cfm

 

[dhengr]

Use 42.64' long beams.

 

[gwynn]

As I think dhengr was suggesting, try to see if you can get the span down enough that you can use 40' beams and make it a standard slab on girder bridge. You could do that with a 13m span, but everyone is happier if the beam lengths are multiples of 10'.

I am somewhat surprised that the concrete slab would be very thick and requires high strength concrete though, maybe we just have different definitions of very thick. 30 tons isn't a huge load for that span length. With Cat 777s I could see the slab depth getting a bit out of hand, but not for a 30ton concrete mixer.

 

[bridgebuster]

I'm with gwynn. 30 T is less than an HS20 truck and there are plenty of 40' bridges in the US.

 

[TomDOT]

I'm guessing HS2O was intended as H2O, not HS2O3 - given the relative abundance of water trucks versus thiosulfate trucks

 

[gwynn]

HS20 is a design truck designation, not a description of what the truck carries. It describes the axle spacings and axle loads a bridge would be designed for.

Though if it was H2SO3 I might have some concerns.

 

[Hoaokapohaku]

The problem is that a cement mixer weighing 30 tons has to pass through it.

Are you sure that is the correct weight? Are you designing for a bridge with a weight restriction below the legal limit? My 11-yard max. mixer trucks have a maximum legal GVW of 79,200 pounds - call it 40 tons.