The Liberty Bridge, along with the Liberty Tunnel, are considered one of the main arteries into and out of the city of Pittsburgh. This corridor provides critical access to the expanding South Hills and surrounding regions of the city. At the time of its construction back in 1928, it was the longest bridge built in the city at 2,663 feet long. The opening was celebrated by one of the largest parades in Pittsburgh history. This past year this historic bridge was set for re-construction by the Pennsylvania Department of Transportation.
This design was unique and the first bridge to be constructed with an Exodermic deck system. This deck system was selected because of its high strength to weight ratio which was a necessity due to the weight limitations on the bridge. The deck system was also an efficient method of construction to provide minimal down time and traffic restrictions.
The general contractor on the project was Joseph B. Fay Company and through our network of companies we played a key role in the project. This gave us the unique opportunity to showcase our technical ability, reliability given the tight construction schedule and the benefits of our cross-discipline integration.
The concrete design for the deck posed the first challenge to our group. In order to minimize the concrete deck weight, lightweight concrete was used for the entire span with 3/8” aggregate to consolidate inside the deck grids. Along with the lightweight nature of the mix, we were also required to accelerate the strength development of the lightweight concrete. In order to meet both the accelerated concrete strength specifications and unit weight requirements, we spent time developing and optimizing several mixtures at our Research and Development Center.
Joseph B. Fay set 948 Exodermic deck panels to cast in place the concrete over bridge spans 4-11 in staged construction. The bridge remained open throughout the project, and in order to minimize traffic disruptions, the deck was replaced one lane at a time. We worked together with Fay to maximize the efficiency of the deck pours and placed spans 4-11, approximately 130,000 square feet in just over 8 months.
Our Frank Bryan concrete plant was able to ramp up production to meet the project schedule while maintaining optimum quality control for the challenging parameters of the mix.
In conjunction with the concrete production, our aggregate division, Neville Aggregates Co., ramped up trans-loading and inventory capacity at the Glenwood Rail Road Terminal to handle the unique size of lightweight aggregate required for the mix. This aggregate was railed in from Carolina Stalite in Salisbury North Carolina.
The last section of the bridge deck, spans 12-14 on the city side, could not be cast-in-place due to traffic patterns as the bridge merged with the city connectors. Our precast division, Concrete Concepts Inc, jumped in and cast the deck panels in just under a 3 month time frame. The same lightweight mix was supplied in-house to our precast division which maintained consistency of materials throughout the entire concrete deck. In the spring of 2017, when Joseph B. Fay resumed construction activities, the precast concrete deck panels were delivered and installed over 5 weekend bridge closures.
Our trucking division, Bryan Logistics Inc, handled the delivery and staging of 12 tractor trailer loads of precast panels on the bridge during the closures. Joseph B. Fay then proceeded to demolish the existing deck and stringers, install new stringers and floor beams, install the precast concrete deck and pour closure concrete to tie the new deck panels together. All in a 56 hour window of continuous work.
The overall success of our portion of the project hinged our our ability to partner with the contractor, engineer and PennDOT to effectively and efficiently communicate common project goals. Maintaining open lines of communication enabled us to optimize concrete mix designs for maximum performance and streamline schedules from precast production to installation, all within our network of companies.
We have been fortunate as a family business to supply challenging projects over our 135 year history and each becomes another chapter in our book. The Liberty Bridge Reconstruction was a group wide effort to provide our customer and ultimately the community with a product that will last for generations.