At my new job we're working in an old railroad repair building, from about 1880 (heavily sandblasted!).
Rigth above our heads are some kinda unusual looking trusses that hold up the barrel roof.
The trusses span about 120 feet, are about 12 feet high, and consist of a straight bottom beam, about 8x14, zig-zag braces, and a curved upper beam also about 8x14.
Running from the top to bottom beams are a number, about 8 steel rods, with plates and nuts on the outer ends.
What confuses me is the rods are of wildly different diameters-- the ones near the middle are about 3/4 inch in diameter. The ones near the walls are about 2.5 inches in diameter!
I can't quite picture how there could be more stress near the walls than at the center, and by that large a factor.
Any ideas?