Box Culvert Shear Under more than 2ft of Fill

[Quade999]

Hi Everyone,

Is anyone here familiar with AASHTO's provision for the calculation of shear capacity for box culvert slab when under more than 2ft of fill? I've attached the relevant parts below.

The wording in Section 5.12.7.3 isn't explicit, but my assumption is that this equation can be used for both the top and bottom slabs of box culvert design with more than 2ft of fill?
Also, it says that when there is less than 2ft of fill, then Section 5.12.8.6 applies. In Section 5.12.8.6.1 it mentions that for one way action, the critical section for shear is as in Section 5.7.3.2 (which says that the critical section is dv away the face of the support). And in 5.12.8.6.2 it says that for one-way action with more than 2ft of fill, refer to back to Section 5.12.7.3. When you have more than 2ft of fill, it doesn't explicitly say to refer to Section 5.12.8.6 (which refers back to the location of critical shear). So my other question is if it is still appropriate to take the critical section for shear at dv from face of support, or whether for more than 2ft of fill, it is taken at the face of support?

Thanks

 

[STrctPono]

See attached. Straight from my "Box Culvert Cheat Sheet". This talks about the critical section for shear check.

You should also see AASHTO 12.11.4.2 if you are already not familiar with it.

 

[r13]

Crack is unlikely to occur under high compressive stress, which tends to close the gap. The sketch provided by you is rotated for ease of visualization on a typical slab/beam-column joint. It should be self evident.