Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.
Issue link: http://concrete.epubxp.com/i/551927
32 • August 2015 www.concreteproducts.com The 3.1-mile New NY Bridge is the single largest bridge construction project in New York's history. The cable-stayed, double span structure, connecting Rockland and Westchester counties across the Hudson Riv- er, will replace the aging Governor Malcom Wilson Tappan Zee Bridge by 2018, thanks to an aggressive construction schedule, light- weight design, and extensive use of near-re- cord scale precast concrete components— some north of 300 tons and engineered as stay in place forms for horizontal, reinforced concrete pier members. Helping to justify the massive new proj- ect were high projected maintenance costs on the old cantilever bridge, estimated at $3 billion to $4 billion over the next 20 years. Also, current traffic of about 140,000 vehi- cles per day far exceeds the capacity of the old bridge, which carried fewer than 40,000 daily during its first decade. The bridge was erected from 1952 to 1955 and designed to last 50 years. Due to more than 10 years of bureau- cratic delays and continuing deterioration of the original bridge, an ambitious plan was devised, beginning with a geotechni- cal investigation in 2013 and reaching a significant milestone as early as the end of 2016—the opening of the westbound span, which will temporarily carry two-way traffic until opening of the second span, scheduled for 2017. Demolition of the old Tappan Zee Bridge will be concurrent with the second span construction, with all work to be com- pleted by early 2018. WHY TZC PREVAILED Submitting bids in competition with two other design-build joint ventures, Tappan Zee Constructors, LLC was awarded the con- tract by New York State Thruway Authority in January 2013. TZC's aesthetically pleas- ing design would require less dredging and less concrete than two competing designs, factors contributing to the firm's low bid of $3.14 billion. The TZC consortium consists of four major partners, American Bridge Co., Fluor Enterprises, Granite Construction Northeast, and Traylor Bros. The winning design features 419-ft. tall outward-leaning concrete towers placed 1,200 feet apart, supporting twin cable- FEATURE BY KEN STADDEN In With The New Deft cast-in-place and precast structure engineering, barge fleet make way for Tappan Zee Bridge replacement An optimized pier scheme, coupled with a construction plan leveraging massive pre- cast sections—chiefy 300-plus ton pier cap (below, fore- ground) and pile cap (below, right) tubs, all serving as stay in place formwork—were cen- tral to Tappan Zee Construc- tors' successful design-build proposal. The 750-ton "Hank Hummel" ringer crane is one of two colossal, foating workhorses deployed to make short work of mammoth pre- cast picks. stayed road decks 139 feet above the water to accommodate ships traversing the Hudson's main navigation channel. A requirement that the bridge go 100 years without major maintenance affected decisions ranging from concrete mix selection to number of precast components specified. Approach spans rest on 48- and 72-in. piles driven to bedrock, or in the case of about one-third of them, driven into deep silt 330 feet below the riverbed to act as friction foundations. Concrete Products examines the cast-in- place and precast concrete aspects of the New NY Bridge in a two-part series. This month's focus on C-I-P structures, especially TZC's three barge-based concrete plants, will be followed in September with visits to the Vir- ginia operations of Bayshore Concrete Prod- ucts and Coastal Precast Systems.