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/306186
The map shows the approximate current implementation of PBES by the states. Graphic: Federal Highway Administration. 46 | ASPIRE , Summer 2011 F H WA F H WA I n Part 1 of this article, published in the Spring 2011 issue of ASPIRE,™ we described the FHWA's Every Day Counts (EDC) initiative. Many EDC events have taken place since the initiative was introduced. Ten regional EDC Innovative Summits were completed with 45 states electing to pursue prefabricated bridge elements and systems (PBES) technology in bridge construction, and four PBES online seminars were conducted. The seminars consist of 14 modules covering all aspects of PBES. The concrete industry efforts and capabilities to support PBES deployment were presented by Susan Lane from the Portland Cement Association and Randy Cox from the American Segmental Bridge Institute. The Civil and Environmental Engineering Department of the Florida International University has established a National Center for Accelerated Bridge Construction to support EDC through education, case studies, and training. Current state of PBEs Concrete technology With PBES concepts, many time-consuming construction tasks are not done sequentially i n s i d e w o r k z o n e s . C o m p o n e n t s c a n b e manufactured off the bridge alignment to reduce on-site construction time relative to conventional practice. An old bridge can be demolished while the new bridge elements are built at the same time, off site, under controlled conditions, then brought to the jobsite to install. This form of accelerated bridge construction (ABC) benefits budget-challenged federal, state, and local transportation agencies, by: • Reducing on-site construction time • Reducing traffic and environmental impacts • Improving work zone and worker safety • Lowering initial and life-cycle costs • I m p r o v i n g c o n s t r u c t a b i l i t y a n d product quality (controlled production environments and curing procedures; convenient, safer access to assembly processes, etc.) Primary Concrete PBEs Prefabricated concrete elements and system assemblies may be effectively used in both superstructures and substructures. For use in superstructures, components include partial- and full-depth precast concrete deck panels, concrete beams with a broad range of shapes and sizes, and composite girders. Superstructure systems and assemblies include large segments of a superstructure, or even an entire superstructure. For use in substructures and foundations, individual components include piles, pile caps, footings, columns, pier caps, abutment wall panels, wing walls, and precast concrete roadway approach slabs. A systems approach would combine many of these components into a total prefabricated structure. With the use of high-capacity, self-propelled modular transporters (SPMTs), an entire bridge may be prefabricated adjacent to or off the bridge site, and then moved into final position. At the Regional EDC Innovation Summits held across the country, many states indicated that they have used one or more of these concrete elements and systems successfully to accelerate construction, reduce disruption to traffic, improve quality and work zone safety, and save costs. The following two examples illustrate PBES concrete systems. NE 8th street Bridge NE 8th Street is the main east-west arterial for Bellevue, Wash., and the primary access route between I-405 and the city's downtown business district. To provide room for a new set of high occupancy vehicle direct connector ramps on I-405, the existing NE 8th Street Bridge over I-405 had to be replaced without causing significant disruption to traffic on either roadway. PBES met the challenge. T h e W a s h i n g t o n D e p a r t m e n t o f Transpor tation (WSDOT) chose a totally prefabricated design that allowed it to stage the bridge alongside the existing bridge, and then move it into place. The south half of the new bridge was constructed in a temporary location south of the old bridge. Eastbound traffic was shifted onto the new portion and westbound traffic onto the south half of the old bridge while the north half of the old bridge was removed and rebuilt. Next, westbound traffic was shifted onto the new north half, and the old south portion was demolished. Finally, the new south half was jacked off its temporary piers and rolled into place. The contractor moved the 2200-ton concrete structure in about 12 hours into its permanent position. The final bridge is 328 ft long and 121 ft wide. PBES techniques allowed WSDOT to avoid taking the bridge out of commission EvEry dAy CouNts: the FHWA technology deployment initiative by Claude Napier, Lou Triandafilou, and M. Myint Lwin, Federal Highway Administration Part two—implementation of Prefabricated Concrete Bridge Elements and systems Book_Sum11.indb 46 7/1/11 10:00 AM