Over the years, the Forum has had a lot of discussions about sagging roofs. Actually, a better term might be "squashed roofs", since they often happen due to snow load. One thing that has always concerned me is that when any arched or peaked roof is squashed to the point of flattening or dishing (sagging), the sidewalls that support it are splayed outward.
Whatever method is used to raise the roof to its original contour must also draw the sidewalls together, and keep them there. Interior cross ties at the top of the walls would do this, but of course the TM has no interior space for cross ties. This suggests that exterior support might be needed. Bruce Perens did this in the thread linked in a previous post.
My concern is that if an aluminum roof-frame member was originally fabricated with an arch, and later was bent in the opposite direction, I am skeptical that it could be simply bent again, back into its original curve, with its original strength. Aluminum doesn't like repeated bends.
I'm not a mechanical engineer, so I'm just noodling here. Gabled house roofs have collar ties to hold the walls together. In the 1800's, massive brick mill buildings in New England had thick iron cross-rods holding the walls together. Ancient stone cathedrals needed flying buttresses to hold the walls together if the wall-to-wall distance was too long for timber cross-ties.
I'm interested in any thoughts, from those whose knowledge is better than mine.
Bill
|