SEATTLE – Something to think about while stuck on I-5 this month: This road repair project is just a sample of many projects across the state that will be equally inconvenient.
The Department of Transportation lists 24 bridges and viaducts in need of new expansion joints. Next summer, the DOT expects to close lanes on the westbound I-90 floating bridge to replace joints that have been cracking for years.
Also in 2008, joints are scheduled to be replaced on the I-205 bridge between Vancouver and Portland, Ore., and on the southbound I-5 bridge over the Lewis River, in the southwest Washington town of Woodland.
The following year, a joint on Seattle’s I-5 overpass to eastbound I-90 is to be replaced. And in 2010, similar work is planned on an I-5 bridge near the Tacoma Dome.
“I expect we’re going to see a lot of this disruption,” said Charles Roeder, a bridge expert and civil-engineering professor at the University of Washington.
But so far, most of the 24 listed projects don’t have funding or a start date. Most of the roads were built before 1969. Age, neglect and growing traffic are taking their toll.
Expansion joints are a crucial part of every bridge because they allow sections of the road deck to expand and contract as temperatures change, without causing the pavement to crack.
Typically, steel strips are installed over the concrete edges at each opening. Over time, cars and trucks carve ruts in the roadway. The steel protrudes and starts to take more punishment. Damaged expansion joints are a symptom of an exhausted roadway.
“Expansion joints simply don’t last as long as other structural elements. They get the living daylights beat out of them,” Roeder said. He said Washington freeways were in excellent shape when he moved here 30 years ago, but they’ve been underfunded and allowed to wear down.
The work being done this month on I-5 is expected to give the roadway another 10 years of use, said Jugesh Kapur, state bridge engineer.
Freeways are designed to last 50 to 100 years, said Patricia Galloway, a Seattle resident and past president of the American Society of Civil Engineers. I-5 is approaching the 50-year mark.
The project has a big impact on traffic because that part of the freeway carries more than 126,000 vehicles a day. Things could be worse if the DOT had to close the whole freeway to lay a new steel piece across the full deck, as a single unit.
Officials found a compromise between traffic disruption and maximum life span of the repaired road by deciding to weld together pairs of steel strips in the center of the road deck, so half the roadway can be open at all times. As a result, the new joints will be less durable.
“Anytime you weld something, you’re much more susceptible to fatigue cracking,” Roeder cautions. Also, it is difficult to fuse the rubberized filling inside the gaps, he said.
Paula Hammond, interim transportation secretary, said her department had to balance engineering needs with traffic needs. “I don’t see any other way,” she said.
Similar joints are wearing out in I-90’s westbound bridge, although the bridge has only been open since 1989. Similar breakdowns have occurred around the country because engineers who originally designed such joints didn’t anticipate metal fatigue, Roeder said.
Kapur said it would be ideal to install each of the main I-90 joints – which are much larger and more intricate than those on I-5 – in one piece. That would mean closing the entire westbound bridge, including express lanes. But the construction strategy hasn’t been decided yet.
If the whole bridge must close, westbound traffic might wind up sharing the eastbound bridge. That’s what happened in Spokane the past two summers, when crumbling decks and joints on its I-90 viaduct were being repaired.
In Seattle, the Aurora Bridge’s joints were replaced a few years ago, while the I-5 Ship Canal Bridge is in good condition, Kapur said.