Music lovers flocked to Stanford University January 11-13, 2013, to attend sold-out performances celebrating the grand opening of Bing Concert Hall. The hall’s 842 seats encircle the 3,200-square-foot stage, creating an intimate environment for both the audience and performers. Acoustic panels on the walls and ceiling, made from fiberglass reinforced polymer (FRP) on top of steel-reinforced concrete, provide optimal sound in the hall and add a dramatic backdrop to performances.
Ennead Architects designed the hall with input from Nagata Acoustics, an acoustical consulting firm. Kreysler & Associates, American Canyon, Calif., assisted in the design and provided the acoustic panels.
“There were two major design factors we had to face: the acoustics requirements and the ease of construction,” says Greg Clawson, project manager for Ennead Architects. Bill Kreysler, president of Kreysler & Associates, and his team developed a series of eight wall panels resembling sails that measured approximately 50 square feet each. They also provided a 127-foot cloud structure for the ceiling made of 80 individual panels.
“When we looked at the design it was obvious that the best material to use would be fiberglass reinforced polymer,” says Kreysler, chair of ACMA’s Architectural Division – one of 12 Composites Growth Initiative (CGI) committees. Fiberglass was strong enough to create sharp edges and complex shapes, allowing tight fitting joints with the precise density needed.
Though FRP met most of the requirements, it was too light for the acoustic panels. They need to be heavy enough to efficiently reflect sound. “The heavier the reflecting material is, the wider the frequency range can be reflected from the surface,” says Dr. Yasuhisa Toyota, president and founder of Nagata Acoustics America. This enhances sound in the hall.
To add weight, Kreysler & Associates cast reinforced concrete onto the back side of the molded single skin FRP panels. Once the concrete cured, the pre-assembled space frame was lowered onto the back and anchored into place, and only then were the panels removed from the mold, assuring they would be reassembled accurately during installation.
The resin used in the application also played a critical role. It was imperative to select a resin that would help the composite material pass two tests used in the construction industry: A flame spread test determines a material’s tendency to burn rapidly and spread flames, and a smoke density test establishes how much smoke is produced. CCP Composites provided a solution: Its NORSODYNE™ H 81269 TF flame retardant polyester laminating resin does not produce smoke. The resin was a perfect choice for fabricating the FRP panels.