Concrete Products

SEP 2015

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.

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Page 35 of 59

34 • September 2015 FEATURE BY KEN STADDEN COASTAL PRECAST: PIERS, PILES, PANELS & CAPS Between April 2014 and May 2015, Coastal Precast Systems (CPS), LLC, Chesapeake, Va., produced soffit panels weigh- ing up to 145 tons each as floor components of two enor- mous 360- x 60-ft. tubs for the foundations of the New NY Bridge's two 419-ft. tower piers, as well as for two 324- x 35-ft. anchor pier foundation tubs. For the tower piers, 36 soffit panels were produced, 18 per tower, measuring 32- x 30-ft. and weighing over 65 tons. Eight 38- x 30-ft. end panels were also produced, weighing in excess of 95 tons. For the anchor pier tubs, CPS produced 18 soffit panels, 27- x 35-ft., weighing in excess of 90 tons, and four 43- x 35-ft. end panels weighing over 145 tons. CPS operates on a parcel along the lower Chesapeake Bay, the waterway access essential to handling and deliv- ery of New NY Bridge-scale product. The massive pan- els were barged north to the work site and assembled to form the tower pier tub floors, after which forming systems were attached for wall pours. Finished tubs were hydraulically lowered into the water to a depth of 9 feet and drained prior to rebar installation and placement of 11,000 yd. of concrete. This floating-tub method was selected by TZC over traditional cofferdams and cast-in-place construction because the Hudson River is more than 40 feet deep, sub- ject to 6-ft. tides, and has powerful currents in its nav- igation channel. Perhaps due to the fluid nature of the design-build process and pressures to remain on sched- ule, CPS President Paul Ogorchock was able to persuade TZC to substitute planned cast-in-place methods with the precast tubs for the 59 pier caps. CPS began producing the 83-ft. and 92-ft. long, 13.5- ft. tall, 10.5-ft. wide pier cap tubs in August 2014 at the rate of about one per week. There are two widths because eastbound and westbound decks are different sizes. A jig was used to stage 64,000 lb. of galvanized rebar on the ground before a crane lifted the reinforcement into one of two forms. The in-house designed forms and bracing with- stand nearly 800,000 lb. of pressure from 0.6-in. diameter galvanized prestressing strand—18 strands per side and 20 strands on the bottom. "The whole thing's prestressed like a big beam," explains Ogorchock. The 59 tubs consumed a total of 7,600 yd. of concrete, averaging 129 yd. apiece. CPS provided TZC a template to aid in pinning the 350- ton tubs to the piers, and mating has gone smoothly as a result. The first tub was picked by the 1,699-ton capacity "I Lift NY" Super Crane in April 2015. "They set their template up and it went down like nothing," Ogorchock affirms. MIXING & TESTING TZC boosted mix production capacity to pace New NY Bridge contract requirements and serve future work, add- ing a second BHS twin-shaft mixer to an existing model for split batching, and bringing peak output to 500 yd./ day. Actual volume could be higher if not for a 90-second mixing requirement from the NYS Thruway Authority, as the mixers have produced concrete exhibiting 95 percent homogeneity within 30 seconds in tests. CPS crews pumped mixes into the forms for the pier cab tubs; for all other jobs, concrete is transferred from the plant into a fabrication enclosure in 4-yd. tubs carried by forklifts. For the initial load and every 50 yards throughout the TZC contract, slump tests and compressive strength tests were performed, using 10 cylinders per batch. A full-time Coastal Precast Systems demonstrated the proposed pier cap scheme with models (opposite page), ultimately providing TZC crews templates showing pin locations. CPS subcontractor Rodbusters in Westbury, N.Y., was able to turn one 32-ton cage (opposite page, right) per week during the pier cap fab- rication schedule. After wet curing of interior surfaces, the 83- and 92-ft. pier tubs were removed from forms with a 400-ton crane (top) and transferred to staging area near the producer's barge slip. Upon placement, the tubs serve as stay-in-place forms (above), the concrete mixes pumped from one of three TZC barge-based plants.

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