VSL, a nationwide specialty-construction company focusing on the design, manufacture, and installation of concrete reinforcement systems, recently received five awards from the Post-Tensioning Institute (PTI).
VSL was recognized this year with an Award of Excellence: Bridges Category for the North Arm Bridge Fraser River Crossing in Vancouver, British Columbia, Canada; an Award of Excellence: Industrial/Special Applications Category for the Holcim Plant in St. Genevieve County, Mo.; an Award of Excellence: - Bridges: Repair/Rehabilitation and Strengthening Category for the New Jersey Abutment of Bayonne Bridge; and an Award of Excellence - Buildings: Repair/Rehabilitation and Strengthening Category for the Utah State Capitol/Base project. VSL also received an Award of Merit for their participation with the Wichita Riverfront Pedestrian Bridge in Wichita, Kan.
PTI's biannual awards program honors superior post-tensioning projects in the construction industry. The judges evaluate the submittals based on creativity, innovation, ingenuity, cost effectiveness, functionality, constructability, and aesthetics. Projects can be submitted into seven categories including buildings, parking structures, slab-on-ground, strengthening/rehabilitation, bridges, industrial/special applications, and international.
"We are honored that five of our projects were selected for PTI awards this year," says Scott Greenhaus, president of VSL. "The PTI awards are well known for recognizing the industry's most challenging projects, which makes this achievement extremely gratifying for our team."
Award of Excellence: Bridges Category
VSL received the Award of Excellence: Bridges Category for the North Arm Bridge Fraser River Crossing in Vancouver, British Columbia, Canada. As the first extra-dosed bridge in North America, the North Arm Bridge is poised to serve the influx of visitors as the city hosts the 2010 Winter Olympics. The $1 million bridge is of precast segmental box girder construction, with two back spans of 456 feet and a main span of 590 feet to allow for marine traffic to pass under it without obstruction. Another first for North America is the use of gensui dampers, which will absorb transverse vibration in the stay cables to protect them from damage. In total, the bridge contains 24 pairs of stay cable anchorages and more than 260,000 feet of stay cable strand.
Award of Excellence: Industrial/Special Applications Category
The Holcim Plant in St. Genevieve County, Mo. also earned VSL top honors in the Industrial/Special Applications category. Consisting of two 151-foot-diameter, 207-foot-tall clinker silos, and two cement "four-pack" silos (in which each individual silo is 79 feet in diameter and 275 feet tall), the cement plant for Holcim Inc. will be one of the largest of its kind in the world when completed this year. A post-tensioned design helped considerably in reducing the amount of mild reinforcement used, and in turn aided in the labor-intensive slip-form construction process. Because the post-tensioning strands were installed, stressed, and grouted after the slip-form process, they remained off the critical path of the slip. Post-tensioning also helped control cracks and improve shear capacity within the concrete silos, since the active reinforcement provides residual compression during all loading conditions.
Award of Merit: Bridges Category
VSL also was honored as the post-tensioning supplier for the Wichita Riverfront Pedestrian Bridge in Wichita, Kan. The project included plans for two cable-stay bridges to increase the area's cycle network and pedestrian footpath access. The 322-foot bridge over the Arkansas River and the 242-foot bridge over the Little Arkansas River feature cable-stayed superstructures with match-cast segmental concrete box girders and a reinforced concrete river pier shape to blend with the aesthetic superstructure features. The superstructure is post-tensioned to the anchor abutments. Concrete segments were transported to the site, erected on false work over the river, post-tensioned, and then lifted off false work as tensioning of stay cables progressed.
Award of Excellence - Bridges: Repair/Rehabilitation and Strengthening Category
VSL also was honored as the post-tensioning supplier for the rehabilitation of the New Jersey Abutment of Bayonne Bridge, which connects New Jersey and Port Richmond on Staten Island, N.Y. The bridge showed signs of deterioration in the form of random cracking of the exposed concrete surfaces. Core samples, visual inspection, and petrographic analysis revealed widespread alkali silica reaction (ASR) as the cause of cracking. The recommended rehabilitation scheme consisted of encasing the existing abutment in new concrete and tri-axially post-tensioning the abutment. The tri-axial post-tensioning pressure on the existing concrete was designed to counteract the internal pressure caused by the expansion of the ASR gel, thus eliminating the prospect of future microcracking of the concrete. To provide the required horizontal compressive stresses, post-tensioning tendons were installed in holes drilled through the abutment concrete. Similarly, rock anchors installed in holes drilled through the abutment to the underlying bedrock were used to achieve the required vertical compressive stress.
Award of Excellence - Buildings: Repair/Rehabilitation and Strengthening Category
Finally, VSL, along with DSI were the post-tensioning suppliers for the Utah State Capitol/Base Isolation and Restoration project in Salt Lake City, Utah, which received an Award of Excellence - Buildings in the Repair/Rehabilitation and Strengthening Category. In an effort to preserve their historic Capitol, and to protect this massive, yet ornate building in an earthquake, the structural engineering team strengthened the building using 256 state-of-the-art seismic isolators under the building. The plan involved permanently resupporting the rotunda with a unique circumferential post-tensioned concrete load transfer scheme. Due to the high strength and stiffness afforded by bonded post-tensioning, the design team produced an innovative, safe and economical load transfer system that protects the historic fabric of the rotunda of the newly renovated Utah Capitol.