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.
Issue link: http://www.aspiremagazinebyengineers.com/i/297033
F O C U S 6 | ASPIRE , Fall 2012 S i n c e i t o p e n e d i n 1 9 6 6 , O B E C Consulting Engineers has been a driving force for evolutions in Oregon's concrete bridge designs. Those efforts continue today, with new concepts for pedestrian bridges, arched bridges, rehabilitation, and high-performance concrete. "We've done a lot of prestressed concrete slabs and bridges over the years, but we've grown a lot," says Guy Hakanson, vice president of technical services for the Eugene, Ore.-based transportation-engineering consulting f i r m . " We w o r k o n a v a r i e t y o f transportation projects, including many types of concrete bridges, from start to finish. And we've expanded to include roadway and heavy civil projects." The firm's "concept-to-construction" approach to project creation gives them a unique perspective on constructability and meeting transportation officials' needs, he says. "We pride ourselves on being able to take a project from initial design through completion of construction. And the quality of the product we produce is viewed by a variety of clients as very high." In recent years, that has meant about 90% of their bridges feature cast-in- place and precast concrete designs, he says. "We try to meet the owners' needs, and many of them prefer concrete bridges for a variety of reasons, including long-term, low maintenance, durability, and competitive initial costs." Tradition of Advances From its earliest days, the company gained a reputation for innovation with its designs for precast concrete, notes Larry Fox, who was named OBEC president last year. That work began with founder Lou Pierce, who produced a variety of designs that advanced the concepts of precast, prestressed concrete bridge design in the late 1960s. The company was the first in the nation to design a segmental, precast, post-tensioned concrete girder bridge, which was used over a county river. "His goal then, as with many of the designs we do today, was to minimize piers in the river and minimize the use of falsework," explains Fox. "That often leads us to precast concrete designs. We did quite a few early on, and we still do them today." To aid that, the firm helped the Oregon Department of Transportation devise precast concrete girder cross sections that are more efficient than the standard AASHTO girders, he notes. An example of their segmental work is the South Santiam River (Grant Street) Bridge in Lebanon, Ore. The three- span, 495-ft-long structure features a combination of precast and cast-in- place concrete sections. It consists of a 55-ft-long precast, prestressed concrete slab approach span and two main spans. The center pier between the main spans supports a variable-depth cast-in-place (CIP) box girder, which extends into both spans. The remainder of each span comprises precast concrete girders that are connected to the box girders with CIP closures and post- tensioning. "The design was created OBEC Focuses on Key Niches 'His goal...was to minimize piers in the river and minimize the use of falsework.' by Craig A. Shutt To meet regulatory and client goals for minimal environmental impacts, the three- span South Santiam River in Lebanon, Ore., was designed with precast concrete girders and a cast-in-place, box-girder section at the pier. All photos: OBEC. Several key areas of expertise—with innovative designs in each—keep OBEC on a successful track AspireBook_Fall12.indb 6 9/18/12 8:57 AM