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Advanced 3D Visualizations Helped Demonstrate Feasibility of Bold Proposal to Replace an Aging Bridge in Oregon
Sundt Construction and Slayden Construction are the Revit Community's Innovator of the Month Pick for January

When the Sellwood Bridge in Portland, Oregon opened in 1925, it was a welcome upgrade from the ferry service that had shuttled passengers across Portland's Willamette River. But over time the narrow two-lane bridge fell into disrepair and scores only a two out of 100 on a federal bridge sufficiency rating scale. Buses and trucks are restricted from using the bridge and the 87-year old structure was designed without seismic considerations. In construction now, Multnomah County is replacing the bridge with a new 2-lane steel deck arched bridge, complete with biking and pedestrian lanes.

"The people who designed the bridge back in the 1920s did not know about the landslide on the west bank they were building the structure on," said Mike Pullen, public information officer, Multnomah County, Oregon. "Over the decades the hillside kept moving, and the bridge did not, resulting in a crunching of the structure. Eventually, 80 years after the bridge was open to the public it had some very severe cracks, and we had to lower the weight limit for vehicles crossing the bridge down to 10 tons, which is very low. We knew we could no longer wait to replace the failing infrastructure."

Image courtesy of the Public Information Office, Multnomah County, Oregon.

The designers of the original bridge were unaware they were building on a landslide area on the west bank of the Willamette River, setting the stage for the structure to ultimately deteriorate dramatically.

Enter Sundt Construction, a firm at the forefront of using Building Information Modeling (BIM) for vertical construction and is now using Autodesk BIM solutions for the virtual design and construction of its horizontal infrastructure projects such as highways and bridges. Beginning in 2011 with the bid phase, and then throughout 2012 and 2013 the Slayden/Sundt joint venture used state-of-the-art software and advanced BIM techniques to generate stunning 3D visualizations and animations to first win the project to replace the aging Sellwood Bridge, and then to communicate effectively with government stakeholders and the general public their innovative idea for how to replace the structure with minimal negative impact on traffic. Sundt Construction and its joint venture partner Slayden Construction became the Construction Manager/General Contractor team that took on this huge challenge.

"The original plan was to build the new bridge in stages to accommodate traffic during construction," explains Eric Cylwik, a virtual construction engineer for Sundt. "Half of the bridge would be built, traffic would be diverted to the new portion of the bridge, the existing bridge would be demolished, and the next portion built in its place."

While bidding for the project, the Slayden/Sundt joint venture proposed a faster, safer, and less expensive method for reconstructing the bridge. They recommended constructing a detour bridge by installing temporary piers and approach spans next to the existing bridge and sliding the original bridge's 1,100 foot steel deck truss onto those temporary structures. The detour bridge would eliminate the cost of steel for two extra ribs running down the middle of the bridge-redundant structural features needed if each half of the bridge was freestanding during construction. This approach also helps avoid the hefty cost of maintaining extra steel over the life of the structure. It would also free up the existing alignment for more efficient construction and immediately improve safety by offloading traffic from the cracked concrete piers supporting the existing bridge.

"The site conditions around the bridge are extremely tight," says Cylwik. "In fact, some adjacent buildings are literally built around the foundation columns of the old bridge. To win this contract, we needed to clearly demonstrate the feasibility of constructing this detour bridge."

Image courtesy of Slayden/Sundt Joint Venture.

Advanced 3D visualization tools were employed by the Slayden/Sundt team to explain how they planned to slide the existing bridge to temporary supports in the river, making room for a new bridge to be constructed in its place.

For precise preconstruction planning and visualization, Slayden/Sundt used Autodesk BIM solutions to create 3D models of the existing bridge and site, the detour bridge, and the new bridge. "We used these virtual models to explore and evaluate construction alternatives," says Cylwik. Slayden/Sundt began by importing point cloud data from a laser scan of the existing conditions into Autodesk Navisworks Manage software and AutoCAD Civil 3D software. "The resulting model gave us the ability to make very precise measurements and assess exact site conditions, helping us find a better way to build the bridge," says Cylwik.

Next the team used Autodesk Revit Structure software to create a 3D model of the detour bridge-with all the temporary framework as well as the actual structure itself-and merged it with the existing site model to make sure it would fit. For example, the team wanted to use four-by-four precast box beams as temporary structural members in a section of the detour bridge that would be very close to nearby condominiums. Using Revit Structure, the team could precisely model those structural components and then measure the distance between the bridge and those nearby buildings (captured as a point cloud of the existing site) to determine if there was adequate clearance. "BIM allowed us to become very familiar with the site, explore our ideas, and validate our approach before presenting it to the owner," says Cylwik.

For the proposal presentation, Slayden/Sundt combined the models in Navisworks Manage and dynamically linked it to a simplified construction schedule to create animated construction simulations. The team also used the models in conjunction with Autodesk 3ds Max to create photorealistic renderings of the project under construction. "These visualizations were critical for helping the owner and other project stakeholders more fully understand and appreciate our construction proposal," says Cylwik. "In fact, they were so impressed with our animations that they hired us (under a separate contract) to make several additional videos that explain the project to the public."

Image courtesy of Slayden/Sundt Joint Venture.

Shown here is a frame for an animation video produced by the team to help stakeholders see how the complex series of steps to create a new traffic access on the west bank side of the bridge.

Slayden/Sundt edged out its competition and was awarded the project in August 2011. Construction kicked off in December 2011 and the Slayden/Sundt Joint Venture continues to use Autodesk BIM solutions during project construction. The detour bridge strategy is paying off, as it is allowing for a sleeker bridge design with fewer redundant features and fewer in-water impacts, reducing the project's cost as well as its environmental impact.

"This innovative construction approach is helping to shorten the project schedule by approximately one year and reduce costs by $5 to $10-million. Without the use of Autodesk BIM software and 3D virtual construction, the owner might not have been convinced of the project's feasibility," says Cylwik.

Today, after the beginning of the project much progress has been realized. The new Sellwood bridge is on schedule for completion in November of 2016. Slayden/Sundt has been successful in using the BIM to communicate to all parties, including the local water authority, to express complicated construction sequencing to minimize impacts to the environment. The bridge construction is an excellent example of current technologies, traditional construction, and building green.

More information
-For complete project history, project progress updates, images and fascinating videos, visit

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Published 2013-11-17 00:00:00