Whether it is Scandinavian innovation, a handmade rope crossing in the Peruvian Andes, or a skyline-defining landmark in a global city, the world would look very different without bridges. For centuries, people have found ways to span rivers, valleys, and rainforests, sometimes working with nature itself to create structures that feel as much like art as engineering. There are millions of bridges across the planet and countless candidates for any best-of list.
A new entry in the National Register of Historic Places may be a spot you regularly pick up dog poop! That's right, Balch Gulch Bridge-spanning the gulch between NW 29th and NW 31st, where many pick up Forest Park's Lower Macleay Trail-was officially designated by the National Park Service in September. Bridge heads likely already know that the steel structure makes use of a load-bearing framework of triangles fastened with flexible pin connections.
Bridges, which are exposed to water and salt, are some of the most vulnerable. About one third of bridges in the United States need to be repaired or replaced, which could cost nearly $400 billion over the next decade. There are plenty of ways engineers cope with rust, from coating the rebar with epoxy to pouring extra concrete to buy some time before seeping water reaches the rebar.
