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Barnes-Jewish St. Peters Hospital, St. Louis

When Barnes-Jewish St. Peters Hospital near St. Louis added a three-story, 66,000-square-foot expansion to its main hospital, the designers envisioned an attractive link to its new addition.

According to Robert Meyer, project architect for Pratt Design Studio of Chicago and St. Louis, creating a high impact, yet contextual transition between the two brick structures was vital to the overall design.

Because the connector, a glass-enclosed elliptical structure, would be adjacent to the hospital's main entry and used as public waiting and circulation, "it is an important element to how the building functions," he said.

Such prominence, combined with its curved glass design and south-facing orientation, required an aesthetically pleasing, yet functional buffer to reduce the heat and mechanical load created by the solar influence on the glass. "We wanted a simple but strong modern statement to accentuate the building," notes Meyer.

Pratt Design Studio's solution was to design a dramatic and contemporary sunscreen created with perforated metal panels from Tampa, Fla.-based McNICHOLS Co. The panels are designed in 0.125-gauge aluminum with 1/2-inch holes in a 1.9-inch straight row pattern with a solid metal border.

Covering a 20- by 30-foot section of the glass area, the curved sunscreen is comprised of 112 anodized perforated aluminum panels, each measuring 12 inches by 5 1/2 feet. The structure is built on a 40-degree curve that matches the radius of the glass.

Four-inch horizontal gaps separate the panels, which are embellished with three horizontal aluminum bands that transition to horizontal sunshades that accentuate the curve of the connector. The same louvered sunshades are also used at the windows on the south façade of the new building.

The panels are secured to intricately designed vertical aluminum channels by stainless steel screws which are placed in decoratively strategic spots. The channels were buttressed and bolted to the building's structural columns. At the base are lights that illuminate the metal after dark.

"The perforation limits the direct sunlight into the space, while still providing visual access to the exterior," says Meyer, while "the curves and slats add a nice level of detail at night."

Together with McNICHOLS' design team and CAD operator, the team laid out the panels on the aluminum channel grid. "There were a lot of details to consider, including connecting the different metals," recalls Curt Allen, project manager for St. Charles, Mo.-based Industrial Sheet Metal Erectors, who worked in association with Image Building Products, St. Charles, to fabricate the sunscreen. The general contractor was Tarlton Corp., St. Louis.

During the six weeks from design to installation, Allen and his fabrication team, using exact field dimensions, devised a system for attaching the aluminum channels to the structural steel to avoid metal contact corrosion.

"We used stainless steel bolts with a rubber membrane to separate the two metals," notes Allen. "Then we prepared the structural steel members to receive the bolts."

Because of the size and positioning of the panels along the vertical channels, the perforated metal needed no bending to create the curve, according to Allen, whose team installed the panels in the field.

A catwalk was built between the glass curve and the sunscreen using structural plates secured to the channels, creating a 3-foot access for cleaning and maintenance of the glass located behind the metal screen.

The completed expansion is home to new inpatient beds, medical offices and a pharmacy. The attractive 2,400-square-foot multi-story glass connector houses public waiting rooms on the second and third floors, with a pedestrian corridor on the first floor. The sunscreen, built for function and aesthetics, has become the memorable image associated with the hospital campus.

"The simplicity of the design belies its intricacy," says Meyer. "Part of the success of this installation is the attention to detail in which a complex assembly of pieces creates a simple, yet powerful element that relates well with the whole design."