No small feat in concrete.

Byline: Bill Bishop The Register-Guard

The biggest bridge under construction in the biggest bridge project in state history is shaping up one piece at a time in the yard at the prestressed concrete plant of Morse Brothers Inc. in Harrisburg.

Picture 73 miles of reinforcing steel bar inside almost 25 million pounds of concrete in 60 piers holding up 6 miles of structural beams to support a one-third-mile stretch of Interstate 5.

That's the essence of the detour bridge under construction across the Willamette River.

Count up $1.3 billion to replace 279 bridges and to repair 86 more around the state over the next 10 years.

That's the scope of the Oregon Transportation Investment Act of 2003.

There's nothing small about either project.

The I-5 bridge replacement over the Willamette is only part of a $29 million project that also includes the cracked I-5 bridges over the McKenzie River near Armitage Park and the much smaller Patterson Slough just north of the Willamette River.

For the three-bridge project, Morse Brothers will make enough prestressed concrete beams to lay end-to-end for 8.4 miles - enough to run down Highway 99E from its plant to neighboring Junction City and back.

Small things add up to big things, and so it is with the very beams that are the backbone of a modern bridge, says Bob Vriem, who has worked his entire 42-year career at Morse Brothers and is the senior estimator on job costs.

Vriem started when the prestressed concrete beam was a hot new idea on the construction scene. Pound for pound, the beams are far stronger than concrete and steel. And they also are far less massive. In fact, most of their volume is Styrofoam.

For durability, they are hands-down better than the reinforced steel concrete beams used to build the original I-5 bridges back in the 1950s and 1960s, Vriem says. Those old beams were doomed to crack eventually and allow water to seep in and corrode the reinforcing steel - which is why the current bridges had an expected life span of 50 years and are now failing.

Prestressed beams aren't prone to cracking. They get their strength from heavy steel cables embedded in their concrete bottoms and sides. They're built inside a steel form that determines their outside dimensions.

The smallest beams for the Willamette River bridge are 4-feet square and up to 115 feet long. Each foot of length weighs half a ton.

Inside each beam are cables that are strung through the length of the form, mostly along the bottom. The cables - 42 of them for the 4-foot box beam - are attached to hydraulic jacks that stretch them with a total of 1.3 million pounds of pull.

When they're all tight as giant piano wires, blocks of Styrofoam are placed inside the form - purely to take up space without adding weight. A cage of reinforcing steel bars is lowered into the form over the Styrofoam blocks. Then poured over everything is a concrete mixture that dries twice as hard as ordinary construction concrete.

When the beam hardens, the tension is released from the cables and the beam takes a slight upward bend under the stress of the cables contracting inside - creating "prestressed" concrete.

When a heavy truck rolls over the beam, its weight is absorbed by the cables within the beam. When the truck rolls off, the cables contract again and the beam springs back up to its original shape, no worse for the wear.

"I don't even know if you could break them," Vriem says. "As far as I know, every piece of prestressed that's ever been built is still functional. Eventually, if you work at it, you will work yourself out of a job."

As permanent as the beams are, they're part of a temporary bridge.

The three detour bridges will return heavy truck traffic to an important length of I-5, eliminating lengthy detours that cost the shipping industry - and, ultimately, consumers - an estimated $38,000 per day, according to state Department of Transportation figures.

Building the temporary detour bridges now will save an estimated $39 million in shipping costs during the years it will take to design and build permanent replacement structures, state transportation officials calculate.

When that time comes, the beams in the temporary bridges will be lifted off and stored until they're needed to replace other failing bridges on rural roads.

"The beams can be picked right off. That part is pretty easy," says Eric Bonn, the Transportation Department's structural design engineer for the detour bridge project.

The temporary bridges are tough, but they aren't pretty and they aren't designed to handle a major earthquake.

"They would certainly handle a minor earthquake. If the big earthquake doesn't come, they'll stay out there as long as you want - 100 years, easy," Bonn says.

But it's not the size, the strength or the design of the bridge project that amazes Bonn.

It's the speed of construction.

For example, Bonn and a team of engineers designed the Willamette River detour bridge in about eight weeks. Ordinarily, such a bridge would be among several under design simultaneously and might take two or three years to complete.

From the start of construction, it's targeted for completion after 352 workdays.

To Larry Lindley, the project - especially the Willamette River bridge - is nothing short of amazing. The retired Transportation Department project manager is awed by the amount of material, the limited work space between high-voltage power lines and a busy interstate, the measures required to protect the river from pollution, the safety challenges - and, like Bonn, the speed of the project.

"Everything has to work in unison. It has to be so well thought out prior to even bidding it. There must have been a team of guys (to) sit down and visualize this project from start to finish," says Lindley, who supervised numerous bridge projects during his 35-year career. "I'm amazed every time I drive past there, the progress they are making. When they finish that job, they're going to look up and say 'We did it!' '

But behind the scenes, Lindley says, such a massive, high-speed project creates a lot of stress for managers and supervisors who have to make snap decisions when problems arise. If he hadn't retired, Lindley says he might have been tapped to manage the project - a prospect that makes his retirement look even better.

As an observer on one of the Transportation Department's tours earlier this month, Lindley strolled around the work sites with a dozen other gawkers.

"It's fun to look at," Lindley says. "But let some of those younger people do it."

BUILDING A BRIDGE

So, just how big is the Willamette River detour bridge?

Concrete: About 24.5 million pounds, including 6 million pounds in piers drilled at least 60 feet deep into bedrock

Reinforcing steel: More than 385 tons of steel reinforcing bar inside the concrete columns and decking

Prestressed beams: Six miles of prestressed concrete beams will carry the load for the 1,930-foot length

Height: Detour bridge will be about 70 feet above the river, the same height as the current bridge, and will stay in place until a permanent bridge is built in seven to 10 years

More info: On the Web at www.odot.state.or.us/region2public /Willamette-McKenzie_Bridges.htm or phone [phone]

Tours: Tours of the work sites offered first Thursday of each month. Willamette tour begins at 9 a.m. at East Alton Baker Park, 512 Aspen St., off Centennial. McKenzie tour begins in Armitage Park at 11 a.m. More information: 744-8080

- state Department of Transportation

CAPTION(S):

Michael Mintanye (left) and John Hill prepare a beam for a concrete pour at Morse Brothers Inc. in Harrisburg. Morse Brothers is making 8.4 miles of the prestressed concrete beams to replace three cracked Interstate 5 bridges.