Annoying vibrations in the balcony of a theatre in Detroit, Michigan were reported by the audience when crowds at the theatre's musical performances danced with the music.
The structure consists of a cantilevered balcony, which is part of the seating area of the theatre. Only the portion of the structure mainly affected by excessive vibration was considered for dynamic studies. The total balcony length along the center of the structure is approximately 100 ft and the total width along the edge is 154 ft. The structure comprises of cantilevers (C), girder (G) and truss (BT). The cantilevers and girders are made of four angles, a web plate and cover plates with different sizes from girder to girder.
To evaluate the vibrations of the balcony structure, a permanent remote vibration monitoring system (RVMS) was designed and installed by the VTL personnel. The RVMS consists of a digital datalogger, a network link interface, several accelerometers, a camera, and a microphone. The RVMS has been used to identify the vibration properties of the structure and evaluate the recorded vibrations of the balcony during live performances at the theatre. Using the collected data from the RVMS, several studies related to the floor vibration serviceability were conducted.
Typical Accelerometers Installed on the Balcony
Time Records of Several Events at the Theatre Measured Using the RVMS