THE CONCRETE BRIDGE MAGAZINE

SUMMER 2009

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

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Basket-weave pattern on bridge soffit. For more information on this or other projects, visit www.aspirebridge.org. retaining walls reaching up to 25 ft tall in order to satisfy architectural requirements and enable constructability within the limited available space. Each horizontally and vertically curving wall followed its own unique alignment while still needing to tie into its neighboring wall. This required multi-dimensional thinking and extensive detailing. To maximize landscape space within the constricted project area, the design team made creative use of stepped structural mechanically stabilized earth (MSE) retaining walls with concrete formliner facings. The architect wanted to minimize the joints in the exposed walls' faces, therefore the team decided against conventional, segmented precast concrete MSE wall panels. Instead, a cast-in-place concrete facing was used on the front side of the MSE walls and the contractor successfully cast the full height of the wall facings in a single placement with no horizontal joints. Full-height precast concrete wall panels were also considered. However, they proved to be less practical and more expensive for the higher walls. The project also incorporated a series of curved cast-in-place concrete cantilever and soil-nail retaining walls, all designed to blend and integrate together. The Vancouver Land Bridge leaves a new legacy, one that links the visitor with the Native American cultural history of the site, commemorates the bicentennial of Lewis and Clark's journey West, and restores a community connection between Fort Vancouver and the Columbia River. ____________ Tim Shell is an associate and Stephen Whittington is a structural engineer at KPFF Consulting Engineers in Portland, Ore. Shell was project manager and Whittington was structural engineer on the Vancouver Land Bridge. A E S T H E T I C S C O M M E N T A R Y by Frederick Gottemoeller The Vancouver Land Bridge is a too-rare example of a crossing that is conceived as an integrated extension of a larger landscape. The bridge and the approach ramps follow a single sweeping curve. The wing walls peel away from of the main curve to follow the contours of the approach embankment. The embankment in turn blends into the natural slopes of the site. The landscape itself crosses the bridge in the edge planters. There are no obvious dividing lines between bridge and ramp or between ramp and site. The site and crossing are a single piece. It is the same quality that Frank Lloyd Wright aimed for in his "organic" architecture. The users' experience refects that. As they approach the crossing, they are attracted onto a ramp that appears to be a natural extension of the landscape. They cross the highway with landscape planting buffering them on both sides, then descend again into the landscape. The patterns on the walls and paving engage users interest and at the same time educate them about the site. The covered overlooks and benches recognize the common human desire to pause and enjoy the view, to rest a moment and absorb what has been seen. The experience is as seamless as the crossing itself. ASPIRE , Summer 2009 | 29 HOW TO combat global warming, reduce the production of greenhouse gases, builda stronger infrastructure. and Contact Headwaters Resources for free technical literature and information on how fly ash use benefits the environment and produces better concrete. When you specify fly ash as replacement for cement in concrete, you help reduce CO 2 emissions from cement production, conserve landfill space, and decrease water usage. You also enhance workability and chem- ical attack resistance, increase strength and produce more durable concrete. SPECIFY FLY ASH (a re c o v e red resource) as a replacement for cement in concrete. 1-888-236-6236 www.flyash.com ASPIRE_Summer09.indb 29 6/5/09 1:51:48 PM

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