Skewed Bridge
Skewed Bridge
(OP)
Hi,
I am trying to understand what actually happens in HEC-RAS when a skew is applied to a structure. In my case, I have 3 culverts (9' span x 5' rise, 8.3' x 5, and 6' x 5') modeled as one structure. I have skewed the culverts 45 degrees, and asked the program to adjust US and DS cross sections. I moved the culverts over since the program didn't adjust for that. I moved them over by comparing the end stations before and after the skew, and determining the reduction ration of the stations. The issue is the downstream flowline was not contained in the structure previously before the skew. Now, after the skew it would seem logical that the downstream XS Flowline would be contained in the structure, but this is not the case. Can somebody please explain to me how the stations are changed before and after? I'm trying to back calculate how the stations became what they are.
Thanks!
*Note: Flow is towards northeast direction in attached photo.
I am trying to understand what actually happens in HEC-RAS when a skew is applied to a structure. In my case, I have 3 culverts (9' span x 5' rise, 8.3' x 5, and 6' x 5') modeled as one structure. I have skewed the culverts 45 degrees, and asked the program to adjust US and DS cross sections. I moved the culverts over since the program didn't adjust for that. I moved them over by comparing the end stations before and after the skew, and determining the reduction ration of the stations. The issue is the downstream flowline was not contained in the structure previously before the skew. Now, after the skew it would seem logical that the downstream XS Flowline would be contained in the structure, but this is not the case. Can somebody please explain to me how the stations are changed before and after? I'm trying to back calculate how the stations became what they are.
Thanks!
*Note: Flow is towards northeast direction in attached photo.





RE: Skewed Bridge
RE: Skewed Bridge
Is it legit to redraw them at the skew (if they're georeferenced) and bring them back in, and just skew the structure in RAS? Do you think this would be a more accurate representation? Is there another way I don't know of?
RE: Skewed Bridge
RE: Skewed Bridge
It's critical that you document how you did it and talk to the bridge designers. They like to pretend that "perpendicular open area" means "open area parallel to the roadway" and they like to stick in piers/abutments that are perpendicular to their bridge, fantastically increasing the scour potential and reducing the open area.