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
A C C E L E R AT E D B R I D G E C O N S T R U C T I O N Accelerated bridge construction (ABC) is often associated with short bridges or short-span bridges and moving full- span components into place quickly. But ABC techniques also apply to longer-span structures, including segmental concrete bridges. These concepts aid in rapid design and construction of bridges, which save costs and minimize disruption to the travelling public. Here are four examples: Victory Bridge ABC techniques have been in development for some years, as can be seen in the Victory Bridge on State Route 35 across the Raritan River between Perth Amboy and Sayreville in New Jersey. The state's first segmental box-girder bridge opened fully to traffic in September 2005—more than two months ahead of schedule. Even more impressive, the first of the twin structures opened to traffic just 15 months after the notice to proceed was received. The second bridge was completed nine months later, according to a report in the Spring 2006 issue of HPC Bridge Views. The bridge's parallel structures feature main spans of 440 ft, a U.S. record for fully match-cast segments. Two side spans on each bridge are 330 ft, while the approach spans vary in length from 142 to 150 ft. The balanced-cantilever method was used to erect the main and side spans, while the span-by-span approach was used for the approach spans. This helped speed the erection process and hasten delivery. Other techniques that helped speed delivery included creating bid documents that were significantly more detailed than usual. This allowed the contractor to work directly from the bid documents rather than create shop drawings, saving both time and money. The bid documents included details of reinforcement bends, segment geometry, and tendon-stressing sequences. They also included electronic files with integrated three- dimensional color drawings for some of the elements. Using this method, the first segment was cast just six weeks after the notice to proceed was issued, getting the project off to a fast start that continued to completion. Earnest F. Lyons Bridge The span-by-span approach to segmental designs also can speed construction, as was shown by the Ernest F. Lyons Bridge in Stuart, Fla. The twin, two-lane bridges were completed eight months ahead of schedule. The 4600-ft-long, bridge features 30 spans at 152 ft plus a first span of 100 ft. Typical segments were 10 ft long, 10 ft deep, and 61 ft wide. A typical span consisted of 15, precast concrete segments, post-tensioned together using ten 19-strand tendons. The spans subsequently were made continuous into six-span units. Despite a permitting process that took two months longer than anticipated, construction was still completed ahead of schedule. Construction delays and some damage also resulted from Hurricanes Frances and Jeanne passing over the site. Three casting beds were set up to cast the 501 segments. Two beds cast typical segments, while the third was created to be interchangeable for pier segments and expansion-joint segments. The precaster used high-early strength concrete and transversely post-tensioned the top slab as soon as possible, allowing beds to be stripped every 12 hours. This ensured a new segment was cast each day in each form. by Craig A. Shutt Segmental Concrete Solutions The Victory Bridge in New Jersey was completed more than two months ahead of schedule. Photo: ©FIGG. The Earnest F. Lyons Bridge was completed within budget and eight months ahead of schedule. Photo: Jim Schneidermann, PCL. ASPIRE , Fall 2012 | 43 AspireBook_Fall12.indb 43 9/18/12 8:59 AM