Hey,
Most authentic covered bridges use trusses for the entire heigth of the side wall. The short span could easily be done with a king-post truss.

Here are some links to king post designs, and one of a TF, 51ft, multiple king-post truss bridge that I built out of reclaimed barn beams.

http://www.nycoveredbridges.org/page41.html
http://www.tfhrc.gov/structur/pubs/04098/04.htm
http://www.coveredbridgesite.com/ny/forge.html
http://www.coveredbridgesite.com/ny/tappan.html

http://i453.photobucket.com/albums/qq254/crwtimberframe/Coveredbridgewinter.jpg

Rooster


Yah-fur-sur, You-betcha, Don't-cha-know!