Construction

Prefabricated Bridge Elements and Systems Cost Study: Accelerated Bridge Construction Success Stories

Chapter 3

The 2-lane 86.8-ft long, 35.0-ft wide single-span Route 1 bridge over the Olden Avenue Connector is a highly-skewed steel girder bridge with concrete deck. Its deck was in very poor condition and required constant maintenance.

The 4-lane 60.0-ft long, 82.2-ft wide single-span Route 1 bridge over Mulberry Street consists of two bridges with a median barrier separating each direction of traffic. The decks of these steel girder bridges were also in very poor condition.

The Route 1 bridge over the Olden Avenue Connector was closed at 7 p.m. on a Friday in August 2005, and traffic was rerouted onto a 5-mile detour. The bridge was demolished in place using conventional methods. The existing abutments were repaired and new bearing seats constructed. The prefabricated superstructure was then erected. The longitudinal joints between superstructure segments were then sealed, and the expansion joints at the ends of the span were completed. The cast-in-place parapets were connected to the outside segments with bars in threaded inserts.

The Route 1 Southbound and Northbound bridges over Mulberry Street were closed at 7 p.m. on a Friday in September and October 2005, respectively, and traffic was rerouted onto a 5-mile detour for Southbound Mulberry, while off-and on-ramps were used for Northbound Mulberry. The construction methods and time required to replace these bridges were similar to the bridge over the Olden Avenue Connector. Parapets and median barriers were cast-inplace concrete.

Each superstructure span consists of 5 full-length segments of varying width, each with two Grade 50W steel girders and a 9-inch thick composite concrete deck (Inverset) system. The 86.8-ft long bridge span over Olden Avenue required W36x182 girders, and the 60-ft long bridge spans over Mulberry Street required W30x99 girders. The 15 segments were designed and fabricated at The Fort Miller plant in Schuylerville, New York, assembled at the plant to verify field tolerances, and trucked to an airport parking lot near the bridge. The segments were required to be onsite 24 hours prior to the start of demolition of the existing bridge. The contract specified high performance concrete for all concrete on the job.

Each bridge is expected to see a 75-100 year service life due to the quality of its prefabricated superstructure, the use of high performance concrete, and the attention given to connection details. Conventionally constructed bridges have an average minimum 50-year life in New Jersey.

Each of the 3 bridges was allowed a 57-hour window from complete closure to reopening of both lanes. If this window was exceeded, a Lane Occupancy Charge would be assessed, up to $10,000 per day. In addition, Substantial Completion of all 3 bridges was required by November 16, 2005, and all work was to be completed by January 13, 2006.

Incentives were also included on this project to encourage the contractor to minimize onsite construction time even further than 57 hours per bridge.

For the bridge over the Olden Avenue Connector, an incentive of $1,500 per hour was specified if the work was completed in less than 57 hours, not to exceed a maximum of $27,000.

For each bridge over Mulberry Street, an incentive of $2,000 per hour was specified if the work was completed early, not to exceed $36,000.

Liquidated damages were also specified. The contractor would be charged $1,500 per hour if he took longer than 57 hours to open the bridge over the Olden Avenue Connector to traffic, and $2,000 per hour if he took longer than 57 hours to open either of the bridges over Mulberry Street.

Also, the contractor would be charged $4,200 per day if the bridges weren't substantially completed by November 16, 2005, and an additional $900 per day if all work was not completed by January 13, 2006.

The engineer's estimate for this project was $ 3.8M. The low bid of $3.5M from Neshaminy Constructors, Inc., was 8% or $297,000 less than the engineer's estimate. There were 5 bidders on this project. The second lowest bid was 10% higher than the low bid.

All three bridges were opened in less than the required 57 hours. The bridge over the Olden Avenue Connector was opened in 56 hours, the bridge over Southbound Mulberry was opened in 51 hours, and the bridge over Northbound Mulberry was opened in 54.5 hours. With all three bridges opened well before Monday morning rush hour, the contractor earned an $18,500 incentive.

Each of the 3 bridges in the New Jersey DOT's first Hyperbuild project was replaced in a weekend, during a total of 6 days over 3 consecutive months. The replacements were completed in significantly less than the 22 months required for conventional design and construction, and they were completed under budget. The design and construction savings, including delay-related user costs, are in excess of $2M.