91ÊÓƵ

Work continues on the yet-to-be-named Portland transit bridge, where progress can be seen in 16-foot increments.

That is the space allotted for crews of carpenters, laborers and masons on the cable-stayed bridge, which is using both a cantilevered approach requiring temporary cable supports and a segmented approach. Both methods keep the bridge in balance, said Vince Castro, construction manager for Omaha, Neb.-based Kiewit Infrastructure Group, which is building the bridge.

“It’s got those two different technical bridge construction methods – the segmental and the cable-stayed,” Castro said. “A lot of bridges have segmental and a lot have cable-stayed. This one has both, so it’s very technical.”

The temporary cables are needed to balance the deck section against the heavy equipment that sits on the bank. As bridge construction progresses, the temporary cables are hopscotched along as permanent cables take their place.

As construction progresses, post-tensioning steel cables, reinforcing steel and electrical conduit are embedded into the concrete formwork, Castro said. In each of the 76 segments across both sides of the bridge, crews are placing rail embedments, which later will tie down the track after it is constructed.

“Once all the components are installed in the segment, the process repeats itself,” he said.

Three key subcontractors – Liberty Steel Erectors, Rebar International and O’Neill Electric – are performing most of the segmented work on the bridge with Kiewit, Castro said.

Roughly 70 full-time employees are working on the bridge, down from a peak of about 100, Castro said. In total, the 7.3-mile, $1.49 billion light rail line, set to open in September 2015, is creating 1,816 on-site construction jobs, according to TriMet.

A key supplier, Ross Island Sand & Gravel Co., makes weekly deliveries of concrete that is poured into each segment after the internal work is finished. Ross Island is projected to deliver 16,830 tons of concrete for the project, Castro said.

Once the concrete is poured, Kiewit moves the construction zone forward using a hydraulic concrete form traveler, which holds the concrete segment in place while it is under construction.

Eventually, the two spans will connect in the middle, said Dave Tertadian, resident engineer for TriMet.

“As we get closer to the middle, there are adjustments that we need to make for each of the 16-foot segments,” he said. “We have to make sure they meet. We are within a fraction of an inch.”

Bridge work is 80 percent complete; the target completion date is May 2014, Tertadian said.

The bridge will accommodate light rail trains, streetcars and buses, and also feature 28 feet of access for pedestrians and bicyclists. Both bridge ends will eventually connect to light rail stations.

After the bridge is completed, workers will need to install and connect signal and power systems for light rail, as well as lighting systems. Those systems should be in place by August 2014, Tertadian said.

Additionally, four to five months of training and testing for systems and operators will be required, he said.

The bridge is set to open in September 2015, when the new light rail line is completed, according to TriMet.