St. Luke's Medical Center Cardiac Center and Patient Tower

Project of The Year: Health Care

St. Luke's Medical Center saw increasing demands in surgery, intensive care and medical/surgical beds.

The Milwaukee hospital sought an innovative design for the addition of its $180 million Cardiac Center and Patient Tower.

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St. Luke's worked with the design team to evaluate several options to maintain patient convenience and staff efficiency on an already congested campus.

The decision was made to build a 12-story facility above an existing six-story parking structure located in the heart of the campus.

A Hospital on Stilts

Once the location had been established, project engineers devised unique coordination, design and problem-solving strategies to accommodate building the structure above the parking garage while meeting the hospital's need for both the garage and hospital to remain fully operational throughout construction.

Dubbed "the hospital on stilts," the tower sits on columns spaced much further apart than a typical building, thus allowing for uninterrupted traffic flow in the garage below. The potential for transfer of vibrations to the tower was eliminated by preventing the columns from having any contact with the garage.

The tower's foundations were constructed on the roof of the garage, rather than at ground level, due to both campus congestion and the need to preserve the existing garage.

The parking structure, which had to remain open to the public throughout construction, was shored and a 65-ton crawler crane was disassembled on the ground and then reassembled on the garage roof to punch 6-ft.-diameter caissons through the existing structure and 100 ft. below ground into bedrock.

A second crane worked from the ground level outside the garage to assist the caisson drilling.

Significant loads were carried by the truss system because of the long spans between the columns.

Trusses from Europe

The design called for trusses that were 32 ft. deep. Each truss weighed up to 1 ton per ft. and required some sections so large that they were not available in the United States.

As a result, they were imported from Europe.

The trusses were erected using a piece-by-piece method of assembly with a tower crane. Truss connections were designed using plates up to 2 in. thick and, in some locations, more than 500 bolts per joint.

The materials fit together to form what was termed the "tabletop" supporting the tower above. The space between trusses provided a convenient location to house the building's mechanical systems.

The stilt design allows for the addition of floors below the tower in the future when the existing parking structure is removed.

Accommodating Medical Operations

Reduction of vibrations caused by large reciprocating air-handling systems was key due to the location of a highly sensitive surgery level directly above the tabletop.

Also due to vibration concerns, the steel-encased, concrete columns that support the tower are up to 5 ft. in diameter and 90 ft. tall and are independent from the parking structure below.

Complete structural models were created to simulate the building's vibration characteristics and identify whether any deficiencies were present in the structure.

As construction proceeded, vibrations were monitored and the model ultimately confirmed that the sensitive surgery floor did perform within acceptable limits.

A building enclosure mock-up was built and tested for structural and thermal elements.

In addition, a unique program of enclosure quality management was developed and implemented. This ensured that the building enclosure was constructed to incorporate the information learned from the mock-up testing and the enclosure components were installed according to specifications.
Strict internal air quality requirements were established.

HVAC ductwork, water and gas piping all came to the site capped so that no ends were exposed. Air handlers and other equipment remained factory sealed until installation to eliminate the possibility for dust and mold issues.

The jury said, "What a project! They went to Europe for the trusses. The staging was complex. The architecture is beautiful. And they did it all over an existing parking facility."