Vibration Studies of a Cantilevered Structure Subjected to Human Activities Using a Remote Monitoring System

Abstract

Long cantilevered balconies used as seating areas in auditoriums, theaters, churches, and stadiums are often susceptible to excessive vibrations because of crowd movements. Measurement and analysis of the responses of such structures when subjected to human movements can provide a reasonable estimate of their dynamic properties. However, it is generally very difficult to artificially excite such massive structures with a measured input force at the same level as that exerted by a crowd. In addition, it is not yet well understood how human occupants’ presence may change the dynamic properties of these structures. This paper presents details of a remote vibration monitoring system (RVMS) installed on a large cantilevered balcony structure to collect the vibration records generated by rhythmic crowd activities. The results of the studies conducted indicate that the presence of human occupants resulted in a consistent reduction in the natural frequencies of the structure and an increase in the damping ratios for higher modes. Conclusions were also drawn regarding the applicability of the damping ratios recommended by a number of standards and design guides for the structure used in this study.