Unique Hybrid Design Takes Garage Up a Level
By Charles Churches, Sr, P.E
In most cities, surface parking is an expensive and inefficient use of valuable acreage. Not surprisingly, to leverage the capacity and the financial potential of a parcel of land, many property owners build multi-level parking structures.
At Ruby Memorial Hospital in Morgantown, WV – the teaching hospital for the West Virginia University School of Medicine – parking had become a significant problem. The growth of the hospital’s new cancer treatment center was putting parking at a premium in its recently constructed downtown garage. With no additional acreage available for surface parking, it was essential for the hospital to expand the capacity of its existing parking garage without enlarging its footprint. Unfortunately, merely adding another level was not a simple task.
The Foundation of the Challenge
When Carl Walker Construction of Pittsburgh designed and built the 225-space precast parking structure for Ruby in 2003, the hospital decided against incorporating foundation structures that could support future vertical expansion. Within two short years, the garage was constantly at full capacity during all hours of the day, and spaces were not available for patients who needed them. Ruby had made a substantial investment when it built the precast structure, and was unwilling to demolish a parking garage that was only two years into its 50-year lifespan. The challenge was to develop a strategy for adding another level – and 105 more badly needed spaces.
“There was really no way to add another level using the same type of precast structural system,” said Len Tsupros, President of Carl Walker Construction. “The foundation system would not stand up to the additional load another level would create. In addition, the garage was now landlocked on three sides due to construction of the cancer center. Even if the foundations could withstand the additional load, it would be physically impossible to raise the additional precast framework into place.”
Tsupros knew he needed to build the new deck using a structural system that was lighter than precast. He also knew that marrying the new system with the existing precast garage would be a significant challenge. To address these challenges, he turned to Charles Churches, P.E., for advice. Churches had worked with Tsupros on the original garage design and was familiar with both the structure and the site.
“When I talked the job over with Len and discussed all the angles, it became immediately clear that a steel-framed, post-tensioned deck was the only solution that was going to work for Ruby,” Churches said. Tsupros and Churches worked together on developing a design, and submitted it to Ruby for review and acceptance. Within a few weeks, approval was received and the job was under way.
To support the load of the additional parking deck, the precast structure needed to be reinforced. In addition, direct ties had to be made between the reinforcements and the existing foundation system.
“Our first challenge was to reinforce the precast center wall of the garage so it could handle the large point loads we were dealing with,” Tsupros said. “We installed cast-in-place columns at 20-foot intervals all the way down the wall. The bases of the columns were tied into the existing caisson and grade system, and the precast floor tees were cut to allow the columns to rise to the top level of the precast structure.”
Once the reinforcement was complete, the steelwork was installed. Center supports of the post-tensioned deck were tied to the new cast-in-place supports. At the perimeter of the building, steel columns were erected on the tops of the original precast structural columns.
“To install the steel columns at the perimeter, we fabricated base plates that fit over the heads of the precast columns,” Churches said. “The steel columns were welded to the plates and then dropped into place. They were secured with bolts that were epoxied into the existing columns. When the steelwork was complete, precast façade panels and column covers were installed to seamlessly integrate the new post-tensioned deck with the original precast structure.”
With the structure in place, the concrete decks were installed. When the concrete was cured, steel plates were installed to make the transition between the end of the precast deck and the beginning of the post-tensioned driving surface. In the meantime, the elevator tower and stairwells were modified to serve the new parking level; life safety systems were installed; and the new deck surface was waterproofed to protect it from the elements.
This $2 million project was completed in five months, and the garage remained open to hospital visitors, staff and emergency vehicles during construction. The additional parking capacity cost approximately $19,000 per additional parking space, and the lifespan of the hybrid garage is estimated to exceed 50 years.
“Carl Walker Construction did an exceptional job on this project,” said Josh Clovis, Project Manager in the Planning Design and Construction Department at Ruby Memorial Hospital. “They understood our challenges, came up with an innovative way to expand our existing garage, and did it all in an extremely short time frame. We were very pleased with the outcome.”
Tsupros also was pleased with his firm’s accomplishments. “This garage is really a one-of-a-kind structure. It demanded that we do some creative thinking that most firms in our business are not set up to do. In the end, we showed that you can effectively bring together two different structural systems, expand parking capacity and lifespan, and end up with a truly attractive parking garage.”
Charles Churches, Sr., P.E., is Director of Marketing and Business Development for Carl Walker Construction. For more information log on to www.carlwalkerconstruction.com
Article Abstract from November, 2008