Re: Wood support Beam and posts - shrinkage
Is the sag noticed in the beam bowing or is the beam lower than it should be?
If the beam is bowing, then it is undersized for the load it is carrying and should be replaced with a suitable sized member or reinforced. If the beam is lower than it should be, then that could be an indication that the piers under the posts are not large enough to support the load and they should be replaced with a suitable sized footing. Either way, it would probably not be a bad idea to get the input from an engineer who can do the load calculations to determine the proper sizing for the footings, posts, and beam.
Structural issues aside, as long as there is no damage, rot, or pests in the posts, then there is no reason to replace them. You can encase them in a decorative column. If you want something unique, you can install load bearing, round, fiberglass columns. Depending on the load, the column itself may be enough, otherwise a steel post inside the column will do the trick.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!