Innovation is frequently a byproduct of adversity.
Faced with a challenge, a team of representatives for the New Jersey Department of Transportation, construction planning company Gannett Fleming and the Federal Highway Administration turned to innovation to create a industry-first bridge design.
The result is an award-winning structure. In 2010, the George Street Bridge in New Brunswick, NJ, (covered in our Spring 2009 issue of Precast Solutions) was ranked as one of the “Top 10 Bridges 2010” by Roads and Bridge magazine and awarded the Eugene C. Figg, Jr., Medal for Signature Bridges at the 27th Annual International Bridge Conference in Pittsburgh, Pa.
Among the many requirements set forth by the public, city and site were minimal disturbance to the area underneath the spans, increased structural integrity and an appearance that that matched the historical look the surrounding community.
When a steel design failed to meet approval, the design team turned to precast arch-barrel design. The high durability and low life cycle costs appealed to NJDOT and the flexibility of the precast pieces allowed the team to achieve the desired aesthetics.
Each arch is constructed of 14 precast pieces and spans 66 feet and is 20 feet tall. In total, the bridge is 593 feet in length and used 128 arch pieces. The precaster used 5,500 psi concrete and the precast pieces were set on multi-column piers.
This design allowed the bridge façade to maintain the historical look while providing the required spans and strength, however it also necessitated a lightweight overfill material to reduce dead load when filling the 12,330 yd3 of space.
Rather than turning to the typical overfill materials, Gannett Fleming broke new ground in precast bridges by using lightweight cellular concrete mix. With a weight less than one fourth of traditional concrete, the mix offered the perfect solution and the bridge project became the first in the world to use precast concrete arches in combination with lightweight cellular concrete overfill.