Headwall Design with Horizontal Span to WingWalls

[EastEng1012]

I am designing headwall with fairly large conduit opening (8-foot diamter). The headwall has wingwalls at 45-degrees. The headwall will need to extend about 3-4 feet above the conduit per the civil grading.

I am designing the headwall above the conduit to span horizontally to the wing walls to resist the lateral earth pressures. I figure I have to check the in-plane thrust from headwall reaction into the wing walls to rely on the wingwall support. I am curious as to how I should approach this check. Does the thrust get distributed purely horizontally along the length of wing wall and then check for resistance against sliding? Also would the wingwall (assuming it resisting sliding) behave similar to a shear wall for in-plane bending.

Or would the reaction distribute at an angle within the wingwall (like an internal strut) and have both a vertical and horizontal component (meaning part of the thrust would be resisted by both the wingwall footing in bearing and sliding friction)?

 

[r13]

I'll consider the headwall and wingwalls for an integral earth retaining structure, and analyzed/designed as thus. Owing to triangular stress distribution, the upper portion of the headwall shouldn't see much earth pressure though. You shall perform stability check on the integral unit.

 

[dhengr]

Rwalker8202:
Look for (search ET) a thread from one or two years ago, probably in the Struct. forum (#507), maybe the Civil forum (#194), essentially the same topic. As I recall, it had several 6’ dia. culverts, 3 or 4’ apart, with an existing system of headwall and wingwalls. He was going to have to raise the existing headwall and wingwalls 3 or 4’ in top elev. Might be something interesting in that thread. In your case, I imagine that the lower 8’ of headwall will span vertically, from a cont. footing, a large horiz. beam, to a second large horiz. spanning beam from wingwall to wingwall, with a beam depth from the top of the culvert (or culverts) to the top elev. of the headwall. The horiz. beam reacts at the top of the wingwalls, which act as shear walls, struts of some sort, if you wish. The footings might have shear keys much like a retaining wall ftg. might, to distribute ftg. sliding forces. The headwall might be thickened around the conduit for the connection of the two and for a spillway, and the like. Your local DOT or DNR might have some std. details for these types of conditions.