Crown Fountain - Construction and Engineering

Construction and Engineering

The Crown family, for whom the fountain is named, donated $10 million of the $17 million construction and design cost. The Goodman family, known for funding the Goodman Theatre, was also a large contributor; the entire $17 million cost was provided by private donations. The initial proposed cost for the fountain had been $15 million.

After two architectural firms refused the contract to make Plensa's design a reality, the firm Krueck and Sexton Architects accepted. Public art was a departure from Krueck & Sexton's residential and corporate office-dominated portfolio, which includes buildings like the Spertus Institute. Collaboration between the artist, architectural team, and consultants proved to be crucial to the success of the project. The fountain's black granite reflecting pool measures 48 by 232 feet (15 by 71 m) and has an approximate water depth of 0.25 inches (6.4 mm). It displays videos on two LED screens, each encapsulated in a glass brick tower measuring 50 by 23 by 16 feet (15 by 7.0 by 4.9 m). The firm designed a special stainless steel T-frame both to bear the load of the walls, which are 50 feet (15 m) high, and to withstand lateral wind forces. The frame holds all the glass blocks and transfers the load to the base in a zigzag pattern. Rods measuring 0.5 inches (13 mm) in diameter anchor to the structure and project into the frame for lateral stability, while triangular corner brackets add support.

The waterfall and the spout are popular attractions.

After several dozen glass manufacturing firms were interviewed, L. E. Smith Glass Company emerged as the company to produce 22,500 glass blocks near the upper limit of the size of press glass formed from hand-poured molten glass and cast iron molds. The process used sand and soda ash heated to a temperature of 2,600 °F (1,430 °C) and "gathered" with a large clay ball resembling a honey dipper. Rather than use a standard plunger to ensure the glass that sagged off the rod spread to the corners of the mold, they relied on gravity. The full mold was annealed (reheated in an oven to 1,100 °F (593 °C)) and cooled. Over the course of four months of production, about 350 blocks were produced per day.

The glass was custom-made at a factory in Mount Pleasant, Pennsylvania, and was fitted into small sections of the frame. Each section was shipped by truck from this plant in the Pittsburgh metropolitan area, with approximately seven sections per tower face. The glass is white glass, rather than the usual green glass that results from iron impurities. This has the tradeoff of increased image clarity, but greater dirt visibility. Each block is 5 by 10 by 2 inches (130 by 250 by 51 mm) with glass thin enough to avoid image distortion. On each block, one of the six faces is polished, and the other five surfaces are textured.

The structure for the blocks was a challenge. At first, the design team had considered switching to plastic blocks, until the team found Circle-Redmont Inc., a prefabricated glass panel company in Melbourne, Florida which specializes in structural glass panel systems and has supplied structural glass sidewalk panels for the New York City Subway system. Circle-Redmont came up with the plan of turning grates on their sides to be used as building elements. The individual grids are 5 feet (1.5 m) tall and either 16 feet (4.9 m) or 23 feet (7.0 m) wide with cell capacity of an average of 250 blocks. Each tower is composed of 44 grids stacked and welded. The combination of the refraction of the glass and the thinness of the metal make the grid virtually invisible.

The fountain uses 11,000 imperial gallons (50,000 L) per hour, 97% of which is recycled back into the system. Getting the water to the spout took ingenuity. Although consideration was given to omitting a LED tile, it was determined that the images would then look as though they were each missing a tooth. Instead, one tile in each tower is recessed about 6 inches (150 mm) to allow the installation of 1 inch (25 mm) clear tubing for the water nozzle. The water regularly spills over the fountain and down the sides of the towers and intermittently spouts from the nozzle. Two essential custom fittings contribute to the artistic vision of the fountain: a custom glass block at the upper edge for guiding the water's descent while remaining unobtrusive, and a plastic nozzle fitted to the stainless steel frame to control the rate of water flow and reduce liability to the city for any injuries sustained by the fountain's interactive participants. The interactive participants are usually children playing in the stream from the water spout or under the cascade. The risk that the spouting water would knock people down made the design both a legal and a physical challenge.

LED lights can be seen behind the front face and are absent from other faces.

The fountains use over one million LEDs. The inner surface of each tower uses 147 smaller screens with a total of 264,480 LED points (each with two red, one blue and two green LEDs). The physical demands of LED screens, in particular the red, green, and blue long-life light bulbs and the requisite circuitry, created three major challenges: supporting the physical structure, combating heat buildup, and optimizing perceptibility of the display. Plensa had used LED fixtures on previous projects, and thus had some experience with these issues. The LED structure is not supported as a single wall (which would be 50 feet (15 m) high), but rather as several segments that are noticeable as visible horizontal bands every few feet: these show where the LED equipment is supported. The heat generated is handled by fans that cool the air at the bottom, that then works its way through the chimney-like tower. Perceptibility was determined to be optimal with LED lights 2 inches (51 mm) behind the glass.

LEDs were chosen because they were viewed as the lowest maintenance option of the possible color changing fixtures. LEDs fit into an electrical circuit, causing illumination by the movement of electrons in the semiconductor material and making a filament unnecessary, so the bulbs never burn out and do not get too hot. Fins were added to the screens to keep direct sunlight from hitting the LEDs. Color Kinetics (now part of Philips Solid-State Lighting Solutions, which is now called Philips Color Kinetics) ColorBlast 12 LEDs fixtures are used to illuminate the tower structures and glass in an attempt to meet Plensa's objective that the towers have a light and translucent appearance, with their internal structures reflecting light from behind the glass surface. The electronics were designed to be adaptable to the time of day, weather and season and to meet the desired century-long longevity and dependability objectives set by the design team in response to the thirty-year directive.

The 9,423-square-foot (875.4 m2) pool used 3 by 3 feet (0.91 by 0.91 m) pavers that weigh 250 pounds (110 kg). The pavers were rested on screw jack pedestals in order to be leveled and shimmed. The pavers had to be perfectly leveled for the water to work correctly because the fountain incorporates numerous sensors to regulate the flow and level of the water.

During construction the underground parking garage remained open. An additional challenge was designing the structure to facilitate interior access for ongoing maintenance and repairs, while accommodating two levels of underground parking underneath. The challenge was solved by combining a T-bar grid to absorb weight with about 150 "outriggers", or "tiebacks", inserted through the video wall to support the glass blocks and absorb wind loads. This design allows for the removal of individual glass blocks for cleaning or repair without disruption to the display. The filtered air inside the towers helps minimize the need for cleaning. Crown Fountain's design not only included interior access for technical repairs, but also incorporated exemplary, non-discriminatory, barrier-free accessibility, because its interactivity is not limited to the able-bodied. The force of the water accounts for the entire range of possible interactive visitors.