We don't define it; we just draw it. For design, typically they are either "elephant ear" (extending parallel to the length of the abutment) or sweptback (parallel to centerline of the roadway and/or edge of the approach slab). We have done some that are at an angle somewhere in between. We don't attempt to label those; we just design and detail them.
Rod Smith, P.E., The artist formerly known as HotRod10
With reference to the axis of a reference point, to which the screwskew angle of the bridge was determined. I suggest to check AASHTO highway geometry design manual for the proper answer.
We typically use straight-extension, flared, or U-back, and the names remain the same even for skewed bridges. I like U-back wingwalls because I think it looks cleaner, but it's usually based on owner (DOT) preferences. My state DOT prefers flared wingwalls because they are almost always the shortest when the orientation angle is based on the grading.
In my experience this mainly comes down to the overall grading the wingwall placement will allow you to different things with grading around the abutment. Every site is different, so its really hard to provide guidance.You need to look at your grading and draw up the different alternatives.
For us, the decision on using elephant ear (extending parallel to the abutment length) or sweptback (extending parallel to the roadway) is normally made based on the height (grade separation) required, with elephant ear wingwalls preferred if the grade difference from behind to in front of the wall is small enough (shallow girders) to keep the length to around 11' or less.
Rod Smith, P.E., The artist formerly known as HotRod10
This is a geometry design and surveying problem. The reference point of the abutment/wingwall must be tied to a station, or a bench mark, same as the roadway alignment itself. The abutment can't be refer to a floating point without bearing and elevation. For structural design, we need two reference points to determine the bridge length, and slop. And for construction, the reference point is required to layout the foundation/structure correctly, and for grading.
Seems like a Bridge detailing (issue) rather than a wing wall type. I could try to use words to describe the various ways to detail Wing Wall Layout. But I suggest trying to obtain some bridge As-Built's for bridges in the DOT jurisdiction the project reside in. I attached a one sample.
