If you can reach it casting from shore : cast upstream and let your bait swing by the pillars. If a float is necessary, do the same if there's any current. And if there is current, try and let your float get to the downstream end of the pillars so it gets halted or stalled in the eddy of the downstream end of the pillar.
If there is no current ... use the wind/wave direction in the same way.
If there is no wind/wave action ... cast past the pillars as far as you can, then use the countdown method to cover all depths around the pillar.
If there's a crossbeam ... cast over it, bring your bait right over top and let it fall on the crossbeam, then slowly drag it off until it falls down the side. Let you bait fall right beside it until it clears the crossbeam and then start your retrieve.
Crappie usually position themselves on a bridge's pillars to where there's the least amount of current, which is usually the downstream sides of the pillars and under a submerged crossbeam between two pillars. They may also position themselves according to the shade provided by the pillars or the bridge itself (in warm weather times) and shallow around the pillars (in cold weather times, as the concrete retains heat from the Sun better than the surrounding water).
And of course, if there are baitfish in these waters and they're close by the bridge .... that's a plus. And if there's any hung up timber on or at the base of the pillars ... that's a plus.