Spawn ... If you can cast beyond the piling, and the current isn't too much ... I'd say go for it !! I'd start out with as small a bait as I could get to go the distance, and work over the ends & side closest to you .... use the countdown method & cover all your depths until you find how deep they're holding. Shaded areas & down current piling being the primary targets. Use of a weighted float, or slipfloat with extra sinker on the line, can be used if necessary.
I used to cast & Vertical Cast bridge pilings on Watts Bar (April/May/Nov) and caught lots of nice Crappie. And it wasn't a big bridge, at all. In fact, it was a 3 piling bridge over a creek.
... cp