State bridge engineers have always had more bridges to repair than funding allows. Maintenance money is at a premium and ever-increasing traffic volumes mean complete closures for extended periods are not an option in many localities. When the New Jersey Department of Transportation (NJDOT) officials saw the Hillman Composite Beam (HCB®) and its potential to reduce maintenance while rapidly replacing existing bridges, they knew it could provide a solution for many of their existing bridges.
The pilot project chosen was in Cedar Grove, a typical high-density suburban town about an hour southwest of New York City. The bridge had many of the constraints of today’s bridges — high traffic volumes, utilities both on the bridge and above, and businesses on either side.
With the bridge chosen, the department’s engineers worked with HCB Inc. to develop plans and details for the new bridge superstructure incorporating NJDOT’s standards. Since the existing bridge was built with prestressed slabs, the lower weight of the HCBs meant the existing abutments could be used with minimal adjustments. NJDOT decided to use 6-foot-wide, three-cell HCB planks, 18-inches deep to match the depth of the existing superstructure and eliminate deck forming.
NJDOT secured Innovative Bridge Research and Deployment (IBRD) program funding from the Federal Highway Administration that allowed for a full-scale test of a prototype beam. After 2,000,000 cycles of fatigue testing, the HCB was found to exceed the capacity of the testing equipment and demonstrate Inventory and Operating ratings in excess of three times the design requirements.
In June 2009, Ritacco Construction placed six HCBs in the first phase to replace the previous bridge’s core slab construction. The six lightweight beams were delivered on one truck and set in place with the excavator the contractor already had on site. The exterior beam was located 6 inches below an existing water line that was temporarily suspended above the bridge. The lightweight HCB was set adjacent to the water line and the crew slid the beam into place. Once the beams were set, the next morning the contractor filled the HCBs and then started to place the reinforcement for the deck and sidewalk.
Less than a month later, the first phase was opened to traffic. In October 2009, the second phase was installed and the bridge was completed in November 2009. In all, the bridge carries four lanes of traffic, two sidewalks, a water main, a gas main and several communication utilities.
Owner: New Jersey Department of Transportation (NJDOT)
Contractor: Ritacco Construction
Completion date: Phase 1 – July 2009, Phase 2 – November 2009
Project Sheet: Click here for downloadable PDF version
“The technical expertise that HCB Inc. provided was fantastic. They answered any questions we had and worked with us to develop some techniques for erecting them. Using HCBs reduced trucking substantially. We were able to move four beams per truckload. If we had used conventional beams, we would have had to use significantly more trucks. Located in a marine environment, Knickerbocker Bridge was a great application for HCBs because it will withstand corrosion better than steel or concrete.”