Hi,
When modeling a bridge in HECRAS, the program looks at the conveyance area under the bridge. Its more concerned with the projected area rather then the type of bridge.
In your specific case, I don’t believe you would need to do anything different. Just model the bridge how HECRAS defaults to, with 2 piers. Enter the pier dimensions as usual. After modeling, examine the bridge crossing and the internal geometry. As long as this 2D image and area looks like and represents the bridge design then the model should be fine.
Further explanation: If the actual bridge design uses hammer head piers (like in the picture), with the pier diameter or width equal to 3 ft, you can enter both the upstream and downstream piers as 3 ft in HECRAS. Looking downstream and the area under the bridge, the 2 piers in alignment in HECRAS will take up the same projected area as 1 pier from the design.
Additional, something you could experiment with is the upstream and downstream inputs for piers. You could enter the upstream inputs and perhaps leave the downstream inputs blank or zero. You could compare these results to my first suggestion.
Hope this helps!
