Bracing Spectacles

Among winners of the Post-Tensioning Institute’s 2008 awards competition, the New Guthrie Theater Center in Minneapolis, Minn., captured Project of the Year, Award of Excellence

Among winners of the Post-Tensioning Institute’s 2008 awards competition, the New Guthrie Theater Center in Minneapolis, Minn., captured Project of the Year, Award of Excellence. Entered in the mixed-use building category by post-tensioning supplier Amsysco, Inc., the project comprises three theaters and a 1,000-space parking garage. A post-tensioned concrete framing solution was implemented for both the main theater and parking structure. An 8-in.-thick sloping slab supported by a radial/circular network of beams and cantilevered girders on five tiers form the main theater’s framing system; and, encapsulated post-tensioning provides maximum corrosion protection and longevity for the traditional, six-level parking garage.

Additional projects were recognized with Awards of Excellence in nine major categories:

Buildings, Commercial: The 1101 New York Ave., Washington, D.C., submitted by Suncoast Post Tension Ltd. Û Eliminating perimeter columns on three sides of the 12-story, 393,000-sq.-ft. building, installation of 12-in.-deep, 6,000-psi post-tensioned concrete slabs with 12-in.-deep drops permitted a 20-foot cantilevered perimeter floor without deflection or vibration issues.

Buildings, Residential: The Cosmopolitan, Seattle, submitted by engineering firm Cary Kopczynski & Co. Û Post-tensioning supplied by Central Steel netted tower floors’ wide-open design.

Bridges: North Arm Bridge Fraser River Crossing, Vancouver, B.C., submitted by VSL Û The first extra-dosed bridge in North America, poised to serve an influx of visitors for the 2010 Winter Olympics, the $1 million crossing showcases precast segmental box girder construction, including two 456-ft. back spans and a 590-ft. main span to allow unobstructed marine traffic. Gensui dampers Û another first for North America Û absorb transverse vibration in the stay cables to protect them from damage.

Industrial/Special Applications: Holcim Plant, St. Genevieve County, Mo., submitted by VSL Û For two 151-ft.-diameter, 207-ft.-tall clinker silos and two cement four-pack silos (in which each silo is 79 feet in diameter and 275 feet tall), a post-tensioned design helped reduce the amount of mild reinforcement required and aided in the slip-form construction process.

Repair/Rehabilitation and Strengthening – Bridges: New Jersey Abutment of Bayonne Bridge, connecting New Jersey and Port Richmond, Staten Island, N.Y., submitted by Modjeski and Master, Inc. Û Recommended rehabilitation consisted of encasing the abutment in new concrete and tri-axially post-tensioning it to counteract internal pressure generated by ASR gel expansion.

Repair/Rehabilitation and Strengthening – Buildings: Utah State Capitol/Base Isolation and Restoration project, Salt Lake City, Utah, submitted by Forell/Elsesser Engineers, Inc. Û To preserve and protect the historic capitol, 256 seismic isolators were used under the building, and a circumferential post-tensioned concrete load-transfer scheme was implemented to resupport the rotunda.

Slab-on-Ground: Barrick Bald Mountain Tire Shop, White Pine County, Nev., submitted by Suncoast Post-Tension, Ltd. Û Producing gold since the 1860s, the mine recently constructed a tire shop and changing pad, totaling 28,800 sq. ft. of slab-on-ground foundation.

Parking Structure: Tampa International Airport (TPA) Economy Garage, submitted by engineering firm Walter P. Moore Û The six-level, 5,600-space garage comprises 5,000-psi cast-in-place concrete in a post-tensioned beam-and-slab structure supported by an ordinary moment frame, consisting typically of 28-in. square columns, 16-in.-wide _ 33-in.-deep post-tensioned beams, and 7-in.-thick post-tensioned slabs.

Student Project: Post-Tensioned Concrete Advantage, submitted by Tylor Paul Middlestadt, Cal Poly San Luis Obispo Û The project, involving simulation of a critical situation in which concrete in a post-tensioned slab fails to achieve design strength, aimed to prove that post-tensioning would mitigate the effects of under-strength, partially cured concrete to the extent that it could withstand the American Concrete Institute specified load test for existing structures.