A bridge north on Lake Shore Drive reopened on Tuesday, only 26 hours after it closed due to cracked steel beams.
City officials say the bridge is again safe for drivers, and that inspections of city and state plans in the next few days for structures of similar design. But the dramatic damage raises questions about the reliability of bridges in other areas, especially because an increase in extreme weather creates more stress on the materials.
A review of Illinois Department of Transportation records found that 400 of the 3,460 bridges in the six-county area are considered "structurally deficient," meaning they need repair or possibly a replacement. That's almost 12 percent. Troubled bridges include heavily traveled bays such as the Lake Shore Drive bridge over the Chicago River, which is just north of the section that closed on Monday, and the I-80 bridges over the Des Plaines River in Joliet.
"We can not sit down and wait for something to happen," said Mark Barkowski, senior vice president of the construction company F.H. Paschen, who worked on the repairs of the Lake Shore Drive bridge. "In any case, the Lake Shore Drive bridge is a wake-up call for Chicago and the state of Illinois."
Cracks in the bridge
The 33-year-old Lake Shore Drive bridge that closed on Monday was not rated as one of the worst bridges in the area; It was rated "fair" on its last inspection in June 2017. The bridge is inspected every two years under federal guidelines, and was due to its next revision in June.
Cracks in the structure were detected by electric crews working on traffic signals near the bridge on Monday morning, according to the Chicago Department of Transportation.
The damage to the bridge, located on Randolph Drive, south of the river, was caused by corrosion exacerbated by extreme weather conditions, said CDOT Commissioner Rebekah Scheinfeld. In late January and early February, the temperature in Chicago went from an arctic of -23 degrees Fahrenheit to about 51 degrees in a few days.
The change in temperature caused the steel to contract, and then it expanded rapidly, Barkowski said. One of the beams that cracked under the Drive was particularly vulnerable to these extremes because it faced off, exposed to Lake Michigan and the sun, Barkowski said. "It is exposed to the weather to a large extent."
A third beam broke on a ramp south of Lake Shore Drive from Wacker Drive, said CDOT spokesman Michael Claffey.
City engineers believe the bridge was "particularly vulnerable" to extreme weather fluctuations due to its design, said Scheinfeld. The cracks occurred in the expansion joint, which was designed to handle weather fluctuations. This time the temperature apparently moved too strong.
The city and the state are planning inspections of similarly designed bridges in the city. The spokesman for the Illinois Department of Transportation, Guy Tridgell, said he believed there were fewer than five.
The northbound stretch of the Lake Shore Drive bridge generally handles around 60,000 vehicles per day. The city is using steel support towers to hold the bridge for 33 years, so that the city can safely reopen it while making permanent repairs.
The engineers contacted by the Tribune were leery of saying, with certainty, what went wrong without having looked at the bridge. But, in general, they agreed with city officials that the sudden change in temperature could have contributed to what happened.
Purdue University professor Mark Bowman said that such fractures are usually caused by a combination of things. A particularly heavy vehicle may have rumbled, perhaps hitting an already weaker connection point. The extreme cold could have weakened the steel to the point that it was more susceptible to all the stress.
Professor at the Illinois Institute of Technology, Gongkang Fu, said that maybe it all started with a crack so small that it could not be seen that it weakened the steel for years, maybe decades, and that it could have been saved from untreated corrosion and become in a deep fracture in the middle of nature. oscillation of the temperature.
A California engineering professor who saw images of the damage said that the corroded state of the expansion joints should have been reported and a remedy recommended at the last inspection. Abolhassan Astaneh-Asl, professor emeritus of civil engineering at the University of California at Berkeley, said the corrosion was probably caused by the salt water dripping into the expansion joint.
Fu and Bowman warned that it can be difficult for inspectors to detect everything. They compared the work with a routine physical examination that can miss serious but hidden diseases.
"The truth is that you can not always detect everything," Bowman said. "It's not that we are Superman and we have X-ray vision."
Fu said the incident shows the dangers of a road system full of deteriorating bridges but unfortunately not very effective to inspect, fix and replace them. Although these fractures are rare, the lower frequency and depth of inspections increase the likelihood that serious bridge problems will not be detected.
The stretch of Lake Shore Drive, for example, was not rated so poorly that it received annual inspections. His inspection window was every two years, and the problem arose towards the end of that window.
"If you do that inspection in 12 months, this probably could have been detected," Fu said.
"In general, if you're looking for someone to blame, it's the money's fault," he said. "We just do not have the adequate funding to address all the problems we probably need."
Other bridges and problems.
Illinois, which has not had an infrastructure capital bill since 2009, ranked fifth in the nation in terms of the number of "structurally deficient" bridges in 2017, with 2,303 bridges or 8.6 percent of the total , according to American Road & Transportation Association of Builders, which used figures from the Federal Highway Administration.
Barkowski, who is also president of the Transportation and Transportation Builders Association of Illinois, warned that there are major problems in other parts of the Chicago area, particularly on bridges along I-80 from I-55 to I-294 He said that part of the Des Plaines River, in particular, is in such poor condition that it may be necessary to close.
The west section of the Des Plaines River Bridge has a "sufficiency" rating of 6 out of 100, the lowest for an interstate in the Chicago area, according to IDOT records. The section to the east scores a little higher 7.4.
IDOT has been planning to replace the bridges as part of a larger reconstruction of that part of I-80. An IDOT spokesman did not immediately respond to a request on Tuesday to develop the agency's plans.
The closure of Lake Shore Drive on Monday was the most dramatic, but not the only bridge problem in the area. A piece of concrete fell from the Oak Park Avenue overpass on the Eisenhower Expressway and landed on a driver's windshield, according to media reports.
Howard Learner, head of the Center for Environmental Policy and Law, said both bridge problems illustrate why Illinois needs to focus on the necessary transportation infrastructure and not shift funds to non-priority ones, such as the proposed extension of the Route 53 Tollway. in Lake County.
Scheinfeld said the incident shows why the region needs reliable and sufficient funds to maintain and repair structures, and to respond to emergencies.
"It is an important reminder of how much we trust and depend on having an infrastructure that is in good condition and is reliable," he said.
Commenting on the closure of the Lake Shore Drive bridge, Mayor Rahm Emanuel renewed his old call for a state infrastructure bill to help avoid situations such as cracked beams. He has also recommended an increase in the gas tax to help pay for it.
"They're going to do a study, they'll give you the cause," he said. "But before this, I've been clear about the need for a transportation bill."
John Byrne of the Chicago Tribune contributed.