The Bridges of Chicago
On May 17, 1673 Pere Marquette and Louis Joliet began their journey to explore the Mississippi river from St. Ignace, Michigan. Their journey traversed what was to become multiple mid-western states, and they stopped in Arkansas after verifying that the Mississippi empties into the Gulf of Mexico. The return trip had indigenous tribes pointing out a short-cut, taking the Illinois river north where they take a portage outside of Chicago. They continue their journey north on Lake Michigan. Marquette and Joliet’s journey and the location of the portage are responsible for the creation of the City of Chicago.
As the city expands there is a need for bridges that traverse the Chicago River. The first movable bridge was built in 1832 and today there are 37 movable bridges, the most frequent design is called the Chicago Style Bascule. Some are over 100 years old with steel coming from a variety of sources. The fastening technology includes rivets, bolts and welding depending upon their age. Richard J. Daley’s Manufacturing Technology Engineering Center has access to older bridges that are being replaced, and we have three of these bridge segments to use in our Materials 2, Testing and Analysis class. This presentation evaluates how many coats of paint were used and its composition, the effects of corrosion, mechanical properties and the microstructure of the segments and fasteners