THE CONCRETE BRIDGE MAGAZINE

WINTER 2013

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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ASPIRE , Winter 2013 | 45 Cedar Lane Bridge over Rockville Pike by dennis F. Campbell, newcrete Products Cedar Lane Bridge over Rockville Pike in Kensington, Md., is located in the midst of an important transportation corridor. The bridge is surrounded by interstate arteries, centered in a very populated community, situated on a major school bus route, and handles an average daily traffc fow of 12,650 vehicles. Be- cause of the bridge's deteriorated condition, a forensic investi- gation was conducted to determine the compressive strength and chloride ion content of the existing concrete. Analysis of the results indicated the bridge had an estimated remaining service life of fve years, making the decision to replace the structure easy. The selected replacement solution needed to maintain the architectural appearance of the original bridge, accommodate pedestrian traffc, limit the disruption to the community, and be constructed on a compressed schedule. Contract specifcations for the replacement included incentives and disincentives, and allowed for 70 days for the road closure. Major steps in the design and construction of the replacement bridge included: • establishing closure requirements and benchmarks, • submitting and approving shop drawings, demolition plans, and erection plans, • installing a temporary bridge and opening it to pedestrian traffc, • fabricating and storing precast concrete elements, • posting a detour route, and • assembling demolition and erection equipment and ready- ing them for use. Geotechnical and foundation analysis showed the existing sub- grade and footings were adequate to support a new bridge and did not need to be removed. The precast, prestressed concrete system included prestressed concrete adjacent box beams; rein- forced concrete pier caps; reinforced concrete abutment caps; and precast concrete architectural parapets that were created as a second cast on the fascia beams. The architectural parapets and sidewalk were initially shown as cast-in-place concrete. In order to meet the limited time requirements for the project, a precast concrete solution was developed to provide the archi- tectural parapet and sidewalk cast on the prestressed concrete beams before leaving the precast manufacturing plant. The structure was assembled by frst setting, and vertically post-tensioning, the pier caps and abutment caps to the existing pier stubs utilizing 1-in.-diameter, epoxy-coated, high-strength, threaded bars. These bars conformed to ASTM A722, Grade 150, Type II and were tensioned to 54 kips. The adjacent box beams were then placed and transversely post-tensioned using 1¼-in.-diameter, Grade 150, hot-dipped, galvanized, ASTM A722 threaded bars, which were tensioned to 120 kips. A 5-in.- thick, cast-in-place, concrete overlay on the roadway and a 4-in.- thick concrete overlay on the sidewalk completed the structure. The concrete components consisted of 36 typical box beams, 8 thickened box beams for the sidewalk, 8 fascia beams with deco- rative parapets, 3 precast concrete pier caps, and 2 precast con- crete abutment caps. The abutment caps were the heaviest com- ponents weighing over 62 ton each. Span lengths were each 42 ft. Notice to proceed was given on February 14, 2011. The road was closed on June 16, with bridge erection completed on July 7. The bridge was reopened on August 6, 2011, well in time for a new school year. Planned and orchestrated for success, the removal and replace- ment construction was completed in 51 days, 19 days ahead of schedule. The application of accelerated bridge construction techniques, using precast, prestressed concrete structural com- ponents provided an economical solution, met the schedule, and produced the desirable end results of this truly unique project. _________ Dennis F. Campbell is an administrator with Newcrete Products in Center Valley, Pa. Erection of precast concrete pier caps. All photos: Newcrete Products. 51 days Completed bridge. AspireBook_Win13.indb 45 12/28/12 11:40 AM

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