Tilt-Up Concrete Association reports that the standing record (since 2003) for tallest tilt-up panel has been bested this year. Seizing first place from
Tilt-Up Concrete Association reports that the standing record (since 2003) for tallest tilt-up panel has been bested this year. Seizing first place from the previous titleholder Û Seven Rivers Presbyterian Church in Lecanto, Fla., boasting a 92-ft. 10Ê-in.-tall panel Û is the Lucky Street parking garage with a 96-ft. 9-in.-tall wall member. Part of a 2,300-space, seven-story parking structure for the Seminole Hard Rock Hotel & Casino in Hollywood, Fla., the 6-ft.-wide stair-tower panel was formed on site and lifted into place by a 150-ft. lattice boom crane.
According to Meadow Burke Products Assistant Chief Engineer Scott Collins, addressing the project’s obstacles involved advanced engineering: A thicker modification from 9.25 inches to 11.25 inches was required in order to overcome deflection. He adds, We made the panel thick and tall with double mat reinforcing six inches on center.
The project garnered the attention of industry experts and brought Meadow Burke Chief Engineer Dave Kelly recognition as a Top 25 Newsmaker of 2006 from Engineering News-Record. Describing bracing challenges presented by the tall panel, Kelly notes, Normally, you need to brace at 60 percent of height. If we had used pipe braces, 80-ft. braces attached to ground 40 feet from the structure would have been necessary, creating additional challenges.
The solution devised by Kelly and Medley, Fla.-based Tiltcrete LLC, the project’s tilt-up contractor, was attaching the panel to the structure, rather than to the ground. We used two temporary points so the crane could be released, and then we connected the panel with many permanent welds, Kelly says.
In addition to a new tallest-panel record, this year has seen the number-five spot nabbed by Polaris Hilton Hotel and Conference Center in Columbus, Ohio. Scheduled to open in April 2008, the facility is a 253-room, nine-story hotel featuring a 40,000-sq.-ft. conference center. The noteworthy panel, forming part of the stairwell shaft, measures 11 ft. 3 in. wide by 85 ft. high and weighs nearly 54 tons. A large area on site was dedicated to the casting bed, and a 300-ton Liebherr crane lifted the panel. Other project panels reached 84-ft. heights.
Determining a way to brace the panels was one challenge presented by their height. Because each stairwell shaft for the nine-story hotel comprises a 12-ft. 7-in. by 20-ft. 4-in. box reaching a height of 95 ft. 8 in., Meadow Burke’s Collins explains, 20-ft. 4-in.-wide lower panels were first installed and conventionally braced to a deadman. The four 85-ft.-tall panels were then erected and welded in place to reach the overall height, he adds.
Tilt-up was also the method of choice for building the project’s 101-ft. 5-in.-tall elevator shafts. Collins notes that six 84-ft.-tall panels were used to construct the three elevator shafts (two panels each).
The decision to use tilt-up panels for shaft walls was dictated by the project’s construction timetable, according to Eric Messerly, P.E., an associate for structural engineering firm Shelley Metz Baumann Hawk, Inc. Using tilt-up panels saved valuable time on a tight schedule, observes Messerly. Additionally, the cost of constructing the walls using tilt-up was less than that for [conventional] cast in place.
Time savings afforded by the tilt-up method were a boon for subcontractor Lithko Contracting. Project coordinator Colin Smith emphasizes that using tilt-up for stairwell shafts enabled completion of concrete work before other trades erected structural steel and installed precast wall and floor components. A safety issue involving workers below the formwork and fighting for crane boom space were thereby eliminated. A cast in place method alternative, Smith asserts, would have called for two cranes Û one for each pair of shafts for the duration of core construction.
Other benefits of tilt-up construction include fewer connections and a smooth interior face on the shaft wall, because the tall panels do not require construction joints at each floor. Building cores provide most of the shear resistance needed for the hotel, and embedded connection plates were designed to transfer the load. Since connecting the panels renders the shaft walls structurally stable, furthermore, wall bracing can be removed to allow floor framing to proceed unencumbered.
An additional change to TCA’s Top Ten list is found in the largest building (footprint) category: a Savannah, Ga., Target import warehouse at 2,029,554 sq. ft. exceeds the previous footprint record held by the 1,708,586-sq.-ft. IKEA Distribution Center in Lebec, Calif. Noting tilt-up’s dominance in the distribution/warehouse construction market, TCA Technical Director Jim Baty affirms, Tilt-Up is often selected for distribution/warehouse centers because of the method’s ability to significantly reduce construction schedules. Largely due to its continued stronghold in that sector, the tilt-up industry is rapidly approaching an annual North American volume of nearly a billion square feet of enclosed building space.
One of the project’s biggest challenges was that the footprint sometimes seemed too small, says Anthony Johnson, project manager of general contractor Ryan Companies US, Inc. of Minneapolis, Minn. To keep the various trades flowing properly and efficiently, intense coordination and fast-track construction were required to ensure that trades on the front end were maintaining the pace needed to support the trades behind them.