Wingwall bolted to culvert or not?

[TehMightyEngineer]

Designing an alternative to a cast-in-place wingwall for a precast box culvert we're doing. The original cast-in-place wingwall was a secondary pour off of the culvert and thus was positively connected with rebar across the cold-joint.

I'm debating whether I actually need a positive connection in my re-design of the wingwall. I'm planning just to leave the wall free-floating. The wall has an extra heavy base and is placed basically on top of bedrock (with a crushed stone leveling pad). Calculated wall deflections are low and I'm planning to have a waterproofing membrane and a filter fabric wrapped, crushed stone drainage layer behind the wall. Backfill has a 3:1 slope down to the wingwall with no traffic loading.

I expect that the wall should have no issues with being separate from the culvert and being loose will allow it to or the culvert to shift slightly as they settle. I've read lots of merits for both connected and free-floating wingwalls. Given my conditions what thoughts do you have on having the wingwall free floating.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[SlideRuleEra]

The wall has an extra heavy base and is placed basically on top of bedrock (with a crushed stone leveling pad).

If the products may be used in other locations, IMHO, attaching should be considered. Where culverts are sometimes used here (swamps, wetlands, tidal creeks, etc.), an unattached wing wall would likely have differential settlement even with high quality base backfill. Worse case... could sink out of sight.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[TehMightyEngineer]

If the products may be used in other locations, IMHO, attaching should be considered.

This wingwall will be used on this job only.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[SlideRuleEra]

TME - With that good foundation, should be fine without attachment.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[amlinerrichard]

It looks like the box culvert sections are tied together and there is no spillway. The wing walls and a spillway should also be tied to the boxes. If there is no spillway added, the wingwalls and some of the boxes will eventually settle. Not for a few years but well before 50 years. when that happens there will be greater and faster erosion at the outfall.

 

[TehMightyEngineer]

The box is going to be filled with 3 feet of soil with flow reducing rock bars to create a natural streambed. The outflow (and wingwall footing) is to be protected by a 2 ft thick riprap apron. The riprap apron will be either directly on (or close to) bedrock.

Good thought on the 50-year design life. I'll put some thought into long-term effects of leaving the wingwall loose.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/