Can a vanilla bridge be safe on top, but have damage floors on bottom?

[Koko Ricky]

I made a vanilla bridge in the standard Doom 2 format, and noticed that, if I apply a damage special to either sector, both will damage the player. This is a bit of an issue because I have an acid pit below the bridge and want it to hurt the player. Is there a way to let the player walk on the bridge without taking damage, but take damage when below it, or is this only possible in more advanced mapping configs?

[ViolentBeetle]

If you can find a way to change textures, it also inherit damage/no damage. I'm not a big expert on bridges.