This book was published only a few years back and is already out of print - You could not buy it and go into the restoration business, but it is a primer on rigging and repair of timberframed barns, and is some of what you're looking for.

http://books.google.com/books?id=u2CNNwA...eFpnCyATrt9yLCA

Amazon lists it as out of print and unavailable, but at least has an image of the cover art -

http://www.amazon.com/Preserving-Old-Bar...5924&sr=1-1

Last I knew ( Last Fall when they finally opened a frame we built for them in '01 to the public ) the New Hampshire Farm Museum still had a couple of signed copies on hand, give them a call I'm sure they'd be happy to ship it to you.

http://www.farmmuseum.org/

It does sound like there is an insufficiency in the barns framing, is it just simple rafters ? With the ties doing all ? What is the GSL in your part of Michigan ?

"We build too many walls and not enough bridges" - Isaac Newton

http://bridgewright.wordpress.com/