If I were an engineer, I would know exactly what pattern this ironwork would make if I depicted it. There are many layers of girders and beams in this bridge. The pattern is made by one layer of built bridge in front of another, from this vantage point. Some of it is made up as I didn't have enough material to fill out the picture. The bridge is actually a long box made up of openwork iron lattice. It's a crane bridge because the box you see hanging from it on the right moves things along a track on the bridge. I'd love to visit a steel mill. There aren't very many still operating in the USA. Most of the steel making has gone overseas to China, India, and other places where labor is cheap. So cherish every bit of real steel you can, sooner or later you will have to make do with wood and bamboo.
Marker ink on sketchbook page, added to with Photoshop, 7" x 2 1/2", May 25, 2015.