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New Sellwood structure stands out in Bridgetown

By Kent Hohlfeld, Architecture and Engineering - January 20, 2017

One of the most expensive and intensive transportation projects in Portland in recent memory was honored by the American Council of Engineering Companies’ Oregon chapter on Wednesday. The organization named the Sellwood Bridge replacement, as submitted by T.Y. Lin International Group, its project of the year for 2016 during its annual awards ceremony.

“It is a great honor anytime you spend all the years we have spent on this,” said David Goodyear, chief bridge engineer for T.Y. Lin International. “It’s what we work for: a happy client and recognition for the works we do.”

T.Y. Lin International served as the lead architect for the nearly $320 million project – the costliest for Multnomah County at the time it moved forward. The firm also served as the lead structural engineer responsible for bridge design alternatives, and as the engineer of record for the replacement bridge. In addition, T.Y. Lin International oversaw bridge, roadway, architectural, electrical, environmental permitting, geotechnical and landslide stabilization design teams. The firm also led the quality control program for the bridge, which opened to traffic in February 2016.

“The project was unique,” Goodyear said of the Sellwood Bridge replacement. “The size doesn’t always mean the most complex. The logistics of this project were challenging. Being able to put together this project from the multiple stakeholders was a big accomplishment.”

Engineers had to figure out how to replace a 1,971-foot-long bridge that spanned the Willamette River. The original 1925 bridge was deemed unsafe when cracks were discovered in January 2004.

The challenges began almost the minute the project did. The team committed to building the new bridge in almost the exact same spot as the original. That meant moving the old bridge 33 feet at the east end and 66 feet on the west end so that it could continue to serve traffic.

“We moved the old bridge over, so it was a challenge,” said Ian Cannon, Multnomah County engineer and transportation director. “Then, after that, we had to build the new bridge with the west end in an active slide area.”

The design team settled on a replacement that stretches 1,976 feet, includes three steel arches supporting a 64-foot-wide deck, two vehicle lanes, two sidewalks and two bike lanes. The project also required modernization of Oregon Route 43 and stabilization of the hillside to the west and above the bridge and highway. The hillside’s slow slide into the river was one of the key reasons the original bridge deteriorated in the first place.

“There were a lot of geotechnical landslide specialists that worked with us,” Goodyear said.

A foundation was designed that would support the deck arch against the hillside. The design team used 3-D modeling to develop a way to anchor a shear pile that included boring 40 six-foot-diameter shafts vertically to depths of 56 to 88 feet. Then they used 70 pre-stressed ground anchors drilled diagonally to depths of 85 to 110 feet into bedrock. The system interacts with the 10-foot-diameter drilled shafts of the arch foundations to counteract further movement.

In addition, seismic goals had to be met. The new bridge needed to be designed to endure a magnitude 9 Cascadia subduction zone earthquake.

T.Y. Lin International has a long history of designing bridges in seismically active regions. The company was the design engineer for the Tilikum Crossing. It also was a lead designer for the new eastern span of the San Francisco-Oakland Bay Bridge as well as multiple bridges in Southern California.

“Building bridges in seismically active areas is kind of our stock and trade,” Goodyear said. “We do a lot of bridges on the West Coast.”

Goals for seismic strength impacted every decision made about construction of the new bridge.

“It controlled how we developed foundation design,” Goodyear said. “The types of foundations we used were selected for their robustness. It governed where the bearings went and were fixed to the foundations.”

Usually a flat horizontal surface is sought for bridges, but that wasn’t possible for the Sellwood Bridge. The bridge’s course takes it uphill. That means the arch spans could not be in balance geometrically. It affected the differential thrust across the interior piers.

“If you look at the arches, the one on the west is smaller,” Goodyear said. “As you ascend the slope, you have different tensions. You have to design it so the thrust on the right and left have to be balanced.”

Another priority for the project team was ensuring that river navigation would be uninterrupted, even during construction. That required not just engineering skill, but coordination.

“The coordination of all the pieces of work that went on was great,” Cannon said. “Working around the different partner agencies was a challenge. We had to work with Portland Parks, the (Oregon Department of Transportation) and others.”

Also, sensitivity to environmental concerns limited when construction could take place.

“Anytime you are working in the water, things are tough,” Goodyear said. “There are environmental limitations. In terms of design we try to minimize the impacts of the foundation we are putting in the water.”

Concrete pours were a tall order. Some 8,200 cubic yards of concrete were used for the bridge’s four immense foundations. Completion of one such foundation required 24 hours. Also, a cooling system had to be devised so that the concrete would not overheat.

Ted Aadland, area manager for Sundt Construction, which oversaw physical construction of the new bridge, said it was the kind of challenge that builders and designers look for.

“We had big piers in the middle of the river,” he said. “There was a limit in pile driving and the amount we can drive. The designers were working on the longest spans they could. That brings a little more flavor to the job and it makes it a little more fun.”

Aadland said he expects the project to become a career highlight for everyone associated with it.

“It’s an iconic job,” he said. “It’s a great looking structure. It’s one I think everybody who worked on it will remember forever.”

2017 ACEC Oregon Engineering Excellence Awards

T.Y. Lin International won the top honor from the American Council of Engineering Companies’ Oregon chapter during its awards dinner Wednesday night, for the Sellwood Bridge replacement project. However, many other companies were recognized. They include:

Best in emergency and water resources

GeoEngineers Inc.: Sanpoil SR21 emergency spill response for Able Clean-up Technologies Inc. / CHS Inc.

Best in transportation

OBEC Consulting Engineers: Sunrise Expressway for Oregon Department of Transportation

Grand awards

Aspect Consulting LLC: Port Angeles landfill stabilization for city of Port Angeles

Cascade Earth Sciences: Monte Cristo Mining Area removal action for U.S. Forest Service

Cornforth Consultants Inc.: US 20 – Pioneer Mountain to Eddyville for Oregon Department of Transportation

Harper Houf Peterson Righellis: Hassalo on Eighth for GBD Architects

Hart Crowser Inc.: Forest Park low tank for Portland Water Bureau

HDR: Bridge Creek Water Supply and Treatment Plant for city of Bend

Shannon & Wilson Inc.: Ridgewood View Park Reservoir and Pump Station for Tualatin Valley Water District

Small project

Otak: Rockinghorse Lane drainage improvement for city of Lake Oswego

Judges’ choice

Kittelson & Associates Inc.: Oregon Avenue protected bike lane for Sky Lakes Wellness Center

Honor awards

AECOM: Light rail transit efficiency projects for Santa Clara Valley Transportation Authority

Akana: Tsaile Dam rehabilitation for U.S. Bureau of Indian Affairs

AKS Engineering & Forestry: Columbia Street regional stormwater facility for city of Sherwood; and Evergreen Drive improvements for city of North Bonneville

Century West Engineering: Redmond Municipal Airport runway 4-22 rehabilitation for city of Redmond – Redmond Municipal Airport

GHD: Harriett powerhouse for Portland General Electric

Harper Houf Peterson Righellis: Daimler North America headquarters for Ankrom Moisan Architects; and Monterey Avenue extension for Clackamas County Development Agency

Integral Consulting Inc.: EVRAZ Oregon Steel riverbank stabilization

Otak: Tenny Creek emergency repair for Clark Regional Wastewater District

Parametrix: Powell Butte Highway roundabout for Deschutes County

PBS Engineering & Environmental: Sixth and Norwood intersection roundabout for city of Camas, Washington; and Vancouver waterfront transportation improvements for city of Vancouver, Washington

WHPacific: Oregon Route 99W – Gaarde McDonald intersection improvements for Oregon Department of Transportation and city of Tigard