Concrete culvert widening

[fa2070]

I'll try to describe the situation as best as I can.

I have to bridge a 7 ft-wide x 36 ft-long (2m x 11m) strip on the side of an existing culvert for truck traffic (no more than 22 Kips. per wheel). Fig. 1a shows how things look now and Fig. 1b shows how the projected lateral access will be.

On the 7 x 36 ft area, just under the grass, there are half a dozen concrete beams B1..B6 which will be removed, or more likely abandoned in place, as they're severely spalled and the rebar completely decayed (Fig. 2).

They will be replaced by steel I-Beams spaced 3 ft. apart from one another. The idea is to anchor the I-Beams to the existing concrete structure of the culvert on one end and to the masonry wall on the other end. Then a 6" concrete slab will be poured over I-Beams. (Fig. 3). Considering this slab will have to resist heavy loads from trucks (Fig. 4) I have thought of reinforcing it with wire mesh mats on the bottom and top sides (Fig. 5).

I'm interested in the study of the 7 x 36 ft. strip only. The rest of the pavement that sits on the ground to the right of the masonry wall is not a concern at all.

Now my questions:
Will this work? Is it going to resist this kind of traffic? Should punching shear be a concern? Is the slab properly reinforced with one wire mesh mat on each face of the slab? Is there anything that I have overlooked and should be changed? How would the slab fail?

Thanks.

 

[cvg]

have you checked this using the AASHTO bridge design manual?

 

[SlideRuleEra]

With all due respect and IMHO, using steel beams for this application is a very bad idea. They are subject to corrosion from damp conditions and cannot readily be inspected or maintained (painted).

"Wire Mesh" (this type

http://www.wirereinforcementinstitute.org/

) is not structural reinforcement. Suggest that you work with an Engineer who has performed this type of design before. A more appropriate structure will likely be made entirely from reinforced and/or prestressed concrete.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[bridgebuster]

Maybe I'm missing something; is the existing a 5-cell culvert? If so, are the members you call beams the walls of the culvert? If they're deteriorated they ought to be repaired.

As far as widening the structure why can't you extend the existing culvert - granted, making a water tight joint will be difficult - or just build a 36' long bridge?

 

[paddingtongreen]

Why the steel beams? If the culvert is good for the load, why not span the slab from the culvert to the new wall

Failing that, if you are closing the culvert with the new wall, why not two walls and a top slab between them, or a new 3' wide culvert section perpendicular to the existing?

Definitely, if the rebar rotted inside the concrete, you shouldn't use steel beams in the same environment.

Whatever, this needs a properly designed structural solution, not a slab with eyeballed mesh reinforcement.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[fa2070]

have you checked this using the AASHTO bridge design manual?

[tab]Does AASHTO cover simple cases like this one? (nothing is simple for me, mind you)

With all due respect and IMHO, using steel beams for this application is a very bad idea. They are subject to corrosion from damp conditions and cannot readily be inspected or maintained (painted).

[tab]That was the first thing I told the contractor. Nobody cares, though, as long as the solution is fast and cheap. That's what they want.

"Wire Mesh" (this type

http://www.wirereinforcementinstitute.org/

) is not structural reinforcement. Suggest that you work with an Engineer who has performed this type of design before.

[tab]AFAIK meshes where [Φ] of wire [≥] 1/4" (or 6mm) can be used as structural reinforcement. But I may be wrong.

Maybe I'm missing something; is the existing a 5-cell culvert? If so, are the members you call beams the walls of the culvert? If they're deteriorated they ought to be repaired.

[tab]No, the object of beams B1..B6 was to support a non-structural concrete lid. Then they put soil and sowed grass on it.

As far as widening the structure why can't you extend the existing culvert - granted, making a water tight joint will be difficult - or just build a 36' long bridge?

[tab]If I extend the culvert then the stormwater from the corrugated pipe couldn't turn 90º and be routed to the floodplains.
[tab]See:
[tab]

Why the steel beams? If the culvert is good for the load, why not span the slab from the culvert to the new wall

[tab]Because the slab under the main road sits on concrete walls, not beams. The beams B1..B6, as flexural members, come to exist in the short span (7 ft) between the curb and the masonry wall. See Figs. 2 and 5.

Definitely, if the rebar rotted inside the concrete, you shouldn't use steel beams in the same environment.

[tab]I know. Neither the contractor nor my employer wanted to follow my advice. Maintenance issues aside, I want to focus on the strength part of the problem for now.

Whatever, this needs a properly designed structural solution, not a slab with eyeballed mesh reinforcement.

[tab]With all humility I would think bridging so narrow a gap (only 7 ft) shouldn't demand a FEA analysis or a bridge engineer. It could be designed from intuition, or from well-known rules of thumb if you will.

Thanks everyone.

 

[paddingtongreen]

" With all humility I would think bridging so narrow a gap (only 7 ft) shouldn't demand a FEA analysis or a bridge engineer. It could be designed from intuition, or from well-known rules of thumb if you will."

Then I have one question. Does this need a PE seal? If it does, good luck because that is a road bridge, small, but still a road bridge.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[fa2070]

Then I have one question. Does this need a PE seal? If it does, good luck because that is a road bridge, small, but still a road bridge.

[tab]No, it doesn't need a PE seal.