Irrefutable 0 ▲ Old Structures Engineering 1 hour ago · Art · hide A view of the steel on the Monroe Street bridge over the Chicago River: It’s a bascule bridge, where the deck pivots upward to open – technically a double-leaf bascule, since each half of the bridge, east and west of the centerline of the river, rotates up. And if you want to get really pedantic, the main structure of each leaf is a pair of pony Pratt trusses. Here’s a nice side view from the Historic American Engineering Survey: The bridge was built in 1919 and rehabbed between 2001 and 2008. Time to look at my top picture again: in 1919, all of those connections would have been riveted. And that steel looks awfully good for 107 years of continuous service. It appears that the rehab included replacing a lot of rivets with bolts and possibly replacing some of the plates in the built-up truss members. If you look at the second link above, there’s a photo along the bridge from around 2014 that clearly shows a mix of modern bolts and old rivets. The presence of modern high-strength bolts… Commenting on Bubbles has been removed. Why? If you want to talk about this post, write to the author, use the comments on their blog if it has them, or reply with a "RE:" post on your own blog. Suggestions? feedback@bubbles.town
