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TOP-DOWN CONSTRUCTION meets the needs of challenging projects, such as those where we need to minimize the impact of construction on the environment.
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Unique project issues bring innovative solutions, like that of top-down construction. When applied to bridge construction, the main advantage is that it minimizes the impact of construction on the environment. Put simply, this approach involves building the structure from the top down by using the permanent structure to support construction equipment. The structure-supported equipment reaches out to drive the next set of piling, then sets precast bent caps and precast deck panels. Both equipment and materials can then advance on to the completed structure. This innovative construction approach eliminates the need for large equipment on the ground (e.g., barges, crane mats) which can damage ecologically sensitive environments, such as wetlands or river valleys. Below, our clients and other construction partners talk about their experiences working on top-down construction projects with the PCL family of companies: I-95 Tomoka River Bridge Widening
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The Tomoka River Bridge project consisted of widening of I-95 in the middle between northbound and southbound lanes. Working between I-95 traffic, PCL constructed the bridge in a top-down manner working off of a crane trestle. The project included 24-inch piling, precast caps and AASHTO girders. The Tomoka River below was lined with revetment mats for erosion control.
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Cross Bayou Bridge
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The original project design required modifications due to environmental concerns that made the construction method prohibitive. PCL provided a Design-Build solution to accommodate all the environmental concerns. The proposal was to build the bridge in such a fashion that all equipment, materials and labor force would work from the new structure “top-down” as it was built, and therefore eliminate working from barges or crane mats within the oyster bed. This method was approved by FDOT and proved to be an ingenious, commendable innovation that satisfied the sensitive environmental concerns.
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SR-45 (US-41) Roadway Reconstruction
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Improvements under this contract consisted of reconstructing SR-45 (US-41) in Sarasota, Florida. Under extreme traffic conditions, PCL constructed three cast-in-place flat slab concrete bridges, concrete bulkhead work, and bridge demolition. Construction of the bridges was accomplished using "top-down" techniques avoiding use of barges in the water.
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