Cortland Street Drawbridge

Cortland Street Drawbridge
Official name	Cortland Street Drawbridge
Carries	Motor vehicles, pedestrians and bicycles
Crosses	north branch of the Chicago River
Locale	Chicago, Illinois
Designer	John Ernst Ericson[1] and Edward Wilmann[2]
Design	Chicago trunnion bascule bridge[1]
Material	steel
Total length	39 metres (128 ft)[3]
Opened	1902
Coordinates	41°55′01″N 87°39′50″W / 41.917°N 87.664°W / 41.917; -87.664Coordinates: 41°55′01″N 87°39′50″W / 41.917°N 87.664°W / 41.917; -87.664
Chicago Landmark
Designated:	July 24, 1991

The Cortland Street Drawbridge (originally known as the Clybourn Place drawbridge)^[4] over the Chicago River is the original Chicago-style fixed-trunnion bascule bridge, designed by John Ericson and Edward Wilmann.^[2] When it opened in 1902 on the north side of Chicago, it was the first such bridge built in the United States. The bridge was a major advance in American movable bridge engineering, and the type was employed for over 50 additional bridges in Chicago alone. The bridge was designated as an ASCE Civil Engineering Landmark in 1981, and a Chicago Landmark in 1991.

Design

This is the bridge type that Chicago engineers may be most famous for. The trunnion bascule has two bridge leaves hinged on opposing riverbanks. The bridge is drawn up by giant trunnion bearings. "Bascule" is French for "seesaw"; the bridge is named for the counterweights which balance the weight of the bridge leaves.^[5]

History

This is the second bridge built on this site. The previous bridge was a swing design which was characterized by a mid-river pier for the swing span. The current (1902) bridge removed the requirement for the mid-river pier, leaving more room for ships.

While the machinery of the current bridge is intact, the bridge is no longer able to open and the leaves are clamped together in the center.^[2] The Cortland Bridge is currently still used for 2-way vehicle traffic, pedestrian, and bicycle traffic.

References

• Encyclopedia of Chicago
• American Society of Civil Engineers

1. ^ ^{a b} "Cortland Street Drawbridge". http://www.ci.chi.il.us/Landmarks/C/CortlandDrawbridge.html. Retrieved 2008-07-16. 
2. ^ ^{a b c} Jackson, Donald C. (1988). Great American Bridges and Dams. Wiley. pp. 197. ISBN 0-471-14385-5. 
3. ^ Cortland Street Bridge at Structurae
4. ^ Hess, Jeffrey A. (1999). "North Avenue Bridge: HAER No. IL-154". National Park Service. http://memory.loc.gov/cgi-bin/ampage?collId=hhdatapage&fileName=il/il0800/il0834/data/hhdatapage.db&recNum=10&itemLink=D?hh:17:./temp/~ammem_xBuT::. Retrieved 2008-07-17. 
5. ^ Cortland Street Bridge, 1953

External links