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Project Profile: Bridging the Divide — Expanding the use of Tilt-Up for unique projects

By Ben Saltzman, Tilt-Up Concrete Association,

When St. Louis University, a private Jesuit institution in St. Louis, Mo., decided to embark on the construction of a covered walkway connecting the South Medical/Research Campus to the brand new Doisey Research Center, they knew they wanted to make a statement. Inspired by his frequent trips to Italy, Father Biondi, University president, envisioned a solid structure reminiscent of Roman arched covered walkways. They knew they wanted to create a pleasant courtyard between these buildings that invited passersby to sit and enjoy the new space. All the contractor had to do was convince them what they needed was Tilt-Up.

Like most ambitious construction projects, the owner was concerned with creating a bold, stylish structure within the constraints of their budget, schedule and site conditions. Concrete Strategies, a full-service design/build general contracting firm headquartered in St. Louis, Mo., knew Tilt-Up was the answer because of its inherent benefits of economy and efficiency. When Concrete Strategies explained that Tilt-Up would shed 20 percent of the cost and four weeks off the schedule when compared to cast-in-place concrete, the University was convinced.

According to Barclay Gebel, Vice President of Operations for Concrete Strategies, the project was originally designed for cast-in-place, but their firm won the contract because they proposed converting the project to Tilt-Up to bring the overall cost of the project in-line with the owner’s budget. “We also presented the facts that demonstrate Tilt-Up offers a safer work place environment, better quality and a faster schedule than cast-in-place,” he added.

With only 9,500 square feet of surface walls, the SLU Cloister Walk is small in comparison to many Tilt-Up structures. However, the project conditions posed many challenges for the design and construction team. The first major challenge was to determine if the Tilt-Up engineer, Alper Audi Inc. of St. Louis, would be able to convert the cast-in-place designed “arc shaped” panels to Tilt-Up. Weighing approximately 55,000 pounds and stretching up to 55 feet long and 16 feet tall, each panel was connected to the footing through a 10-foot wide leg on the low end of the arc. The panels were designed to cantilever both vertically and horizontally with a rigid connection to the footing with embedded dowels. The panels were not connected to each other to allow for differential settlement without cracking the panels or their brick veneers.

Another challenge was determining if the panel lift and brace engineer, Meadow Burke, could provide a lift design for the uniquely shaped panels. The first obstacle would be calculating the center of gravity for each panel, because they contained complex curves and changes in thickness throughout. The second feat was coordinating the lifting, because of the multiple embeds including structural plates, dove anchor slots, PVC drains and areas of congested reinforcing.

Once the team decided the project could be converted to Tilt-Up, Concrete Strategies faced several construction challenges. Panel layout and forming was complicated because of the unique radial shape of the panels, which had o be formed from the radii of one panel to another. In order to effectively form the panels, the contractor programmed one station with all radius points and panel joints. The panel reveals needed to be modified to work with these panels, and Greenstreak was able to accommodate the contractor allowing the Stix® reveals to bend on the tight radii the project required without compromising quality. Panel erection posed another challenge because the rounded panels could not be rotated plumb from the ground, but rather had to first be lifted flat from the slab then rotated in the air with two lifting beams. One side of the panel was then erected on a steel tube that extended from a previously erected panel. The panels were then set on one another, transferring the load to the foundation.

The SLU Cloister Walk project also incorporated some innovative features and architectural details, which contributed to the overall complexity and success of the project. For the brickwork installed on the exterior face of the panels, the contractor cast all dovetail slots and brick concrete lintels on the upward facing side of the cast panels. For the roof draining system, they needed to cast the PVC roof drains and walkway lighting into the Tilt-Up panels. The project also utilized self-consolidating concrete in order to achieve the high quality finish of the Tilt-Up panels.

The overall budget for the Cloister Walk project was approximately $1.8 million, and Concrete Strategies completed the Tilt-Up concrete work in less than two months. Apart from meeting the owner’s expectations on budget and schedule, Concrete Strategies attributes winning the contract to their membership in TCA. Utilizing the 2007 TCA Achievement Awards DVD helped demonstrate to the owner that the project could be done with Tilt-Up to achieve a high- quality end product.

Barclay Gebel believes the success of this project is not only a benefit for their firm, but the Tilt-Up industry in general. “We expanded our own Tilt- Up design and field capabilities as a company by doing this project,” he said. “We feel that we also raised the bar for the Tilt-Up industry regarding what types of projects can be successfully completed using Tilt-Up.”

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TILT-UP TODAY, a publication of the Tilt-Up Concrete Association, is THE source for Tilt-Up industry news, market intelligence, business strategies, technical solutions, product information, and other resources for professionals in the Tilt-Up industry. A subscription to TILT-UP TODAY is included in a TCA membership. Subscriptions for potential TCA members are also available. If you would like to receive a complimentary subscription to the publication, please contact the TCA.