Here's an example of how we treat the end skewed section of a precast box culvert. I realize you are dealing with CIP, but the concept is the same. We use a 4'-0" design beam width, and a span length equal to the skewed length. Reinforcing is "fanned out" from the short side and placed so that...
If the box culvert is rectangular in plan view, and is simply oriented at an angle compared to the direction of traffic, then I agree that the span is 6m. However, if the ends of the box culvert are skewed to match the traffic direction, then the design span at those skewed ends would need to be...
