Jordan Strub was riding his bicycle on the Pikes Peak Greenway trail when he looked up at the bridge carrying Fillmore Street high over the trail and Monument Creek.

Between the horizontal steel girders of the bridge and the vertical concrete piers that rise from the creek bed is a series of stubby, rectangular steel supports - sort of like big shoe boxes - rounded on top and bottom.

Strub noticed that many of the supports are no longer standing straight up and down. In fact, several are tilted at alarming angles.

He wondered if it was an optical illusion because of the slanting bridge, which is lower on the east and rises to meet the west abutment.

He wondered if the bridge, built in 1961 and widened in 1971, had been moving.

He wondered if the bridge was safe.

"I wondered ‘does anyone else ever notice things like this?' " said Strub, who took photos that are posted on my blog.

Turns out, they do. A number of people besides Strub have seen the twisting, tilting rockers and contacted the city over the years.

But Strub had trouble reaching city engineers, so he contacted Side Streets - or, in this case, Side Bridges - and we got answers.

"The bridge is stable and fine," said Dan Krueger, a senior civil engineer in Colorado Springs' engineering department.

He explained that the tipping steel shoeboxes are called rocker bearings or panels. They were designed to rotate to compensate for movement in the bridge.

In this case, Krueger said, the bridge slid east over the years and pier 3 shifted west in a flood years ago, causing the rockers to twist and tilt.

Rockers were common on bridges of the era, although they were abandoned by engineers decades ago in favor of sliding teflon-coated steel plates and thick slabs of neoprene.

Until 2007, the bridge was owned, inspected regularly and maintained by the Colorado Department of Transportation. It noted the rocking rockers as early as 1998, said Jeff Anderson, who manages the CDOT's bridge inspection program.

"They look funny when they start to tilt," he said.

Funny? Scary might be a better word.

Anderson said CDOT experts measured the rockers on pier 3 at a 10-degree slant. Pier 2 rockers tilt just 5 degrees. Rockers must reach 15 degrees before CDOT recommends taking action.

"It's safe," Anderson said.

So why not pull them out and straighten them up?

"You have to jack up the bridge and reset the rockers to vertical," Anderson said. "It's not really very easy."

At one time, CDOT hoped to rebuild the Fillmore and Interstate 25 interchange and replace the bridge. But the money ran out so it sits.

Despite CDOT's assurance the rockers have not moved in years, city experts do a visual check every 90 days, and survey crews verify its stability every six months.

"We're just keeping an eye on it," Krueger said. "We will monitor it indefinitely."
-
See photos on my blog at
gazette.com/blogs/sidestreets