Brige apron

[SKJ25POL]

Hi,
Couple questions to experts to educate me:
1- May I ask what's the purpose of the bridge apron,(the sloped concrete slab)?
2- Is it and shall it be connected to abutment?
3- If damaged can it be replaced by rip rap?

Thank you very much and Happy Holidays.
Respectfully.
Skj

 

[bridgebuster]

1- May I ask what's the purpose of the bridge apron,(the sloped concrete slab)? It's a form of slope protection
2- Is it and shall it be connected to abutment? No and no
3- If damaged can it be replaced by rip rap? Yes, (although some people have different definitions of rip-rap). However, crush stone is an acceptable form of slope protection.


As an afterthought...stone is easier to place and grade on a slope than concrete. Although, in urban settings, pavers or concrete look better than stone and less liability.

 

[SKJ25POL]

bridgebuster (Civil),
Thank you so very much for your kind response.

1- May I ask if the apron is not mechanically attached/connected to the bridge abutment then what is keeping the apron (concrete slab0 fro sliding down?
2- Also is the rip rap as efficient as concrete apron in terms of erosion ?
Thank you
Skj

 

[bridgebuster]

You're welcome SKJ25POL

1- May I ask if the apron is not mechanically attached/connected to the bridge abutment then what is keeping the apron (concrete slab) from sliding down? If the slope isn't very steep, it shouldn't slide. I've also seen it "keyed in" at the toe.

2- Also is the rip rap as efficient as concrete apron in terms of erosion ? Concrete will give you virtually 100% runoff; gravel is about 60 to 70% runoff but the runoff for gravel also depends on the permeability of the underlying soil. Rip rap isn't a permanent solution but it's commonly used because it's cheap and easy to place. It can get overgrown with vegetation whereas you won't get anywhere near as much of that with concrete.

 

[SKJ25POL]

bridgebuster (Civil),
Thanks again for your reply and great knowledge. Hope you don't get frustrated me asking more.
So,
1- what is the bases of design of the apron? How thick we make the slab? What is the bases of the thickness of the apron?
2- Where I can find some information on design/sizing these aprons?

I tremendously appreciate your help/response and great knowledge.

Respectfully,
Skj

 

[bridgebuster]

You're welcome again SKJ25POL

what is the bases of design of the apron? How thick we make the slab? You can treat it like a sidewalk slab on grade. 4 to 7 inches thick. At the bottom you may want to thicken it to 7" or more if there's a chance a vehicle might ride on it. Well compacted subbase and a gravel base and you should be set. What is the bases of the thickness of the apron? Probably isn't any basis although with a stone apron velocity and flow comes into play and it affects the size of the stone. I'm sure every DOT has a standard detail they prefer.

2- Where I can find some information on design/sizing these aprons? Try this link, NYSDOT standard details for embankments. They only have details for stone slope protection, but you can modify them for what you want to do in concrete Link

 

[BridgeSmith]

Our slope paving is typically 4" thick, with welded wire fabric reinforcement. On steeper slopes we've keyed it in at the toe and sometimes added shear keys at intermediate locations on the slope.

 

[SKJ25POL]

bridgebuster (Civil), Thank you so very much for your comprehensive response. Happy New Year 2019 to you in advance.

HotRod10 (Structural), Thank you for your comment too. Greatly appreciate it. If you are in US or Canada, Happy New year.

Respectfully,
Skj

 

[bridgebuster]

you're welcome and Happy New Year to you.

 

[OSUCivlEng]

I've always thought this was a rather interesting slope wall. What? We don't need a longer span!