Police said seven vehicles were damaged by the falling debris when the equipment detached from support cables and fell onto Michigan Avenue.
The Chicago Department of Buildings said the scaffolding system failed and part of it became detached from the roof, causing it to fall.
Tyrone Pullum, 57, was struck by a falling cable.
"When it happened he was crossing the street and he heard a loud noise. He said it sounded like the building was coming down and he ran," said his wife Dr. Sylvia Begay-Pullum. "He told me his left side and his back have been injured. He's in pain."
Pullum is a security officer and pastor.
Authorities said the piece that fell from the 10th floor of the building is called a davit, which holds the scaffolding to the top of the building, and weighs 300 lbs.
"It is an ornamental piece of aluminum that holds the scaffold cables as the scaffold goes up and down the buildings," Chicago Fire Department Chief Tim Walsh said.
Shortly after 5 p.m. repair crews on the scene broke the window next to where the piece of scaffolding was hanging from the 10th floor. Crews then removed it and pulled it inside.
Michigan Avenue was closed between Lake and Randolph. Randolph Street was closed between Michigan and Wabash while repair crews worked to secure the scaffolding and clear debris and broken glass from the area.
Officials said the streets would remain closed until all the broken windows were repaired. Officials also worked to secure any broken glass around the building and make sure the area is clear for people to walk around and drive through. Until that all clear is given, roads would continue to be blocked.
Michigan Avenue reopened between Lake and Randolph just after 8 a.m. Wednesday.
The cause of the failure remains under investigation.