Effects of Vibrations on Structures: Overview and Case Studies

Abstract

This paper explains the use of practical methods and records of input motion in the investigation of vibration effects on structural subsystems (such as floors) and components. Six example cases are presented in which the analysis of vibration resulted in appropriate intervention methods for controlling vibration and abating its damaging effects. Each case demanded a different level of serviceability, for which remedial measures had to be implemented to meet the particular serviceability demand. Cases 1 and 2 each concerned vibrations induced in a floor system as a result of occupants’ exercise activities. Suggested solutions included doing nothing, implementing simple alterations and control of the activities, or relocating the exercise area. Case 3 involved vibrations in balconies in a church assembly area. The suggested solution in this case involved design of a dynamic absorber with an optimum installation location to alleviate the vibration effect. Case 4 dealt with the vibration of a floor system caused by operating commercial washing machines. The suggested solution included the installation of vibration isolators and absorbers and/or implementing structural retrofit to increase floor stiffness. Case 5, vibration in a hospital surgery room, and Case 6, vibration in a portable classroom, involved detailed data gathering and identification of the sources of vibration. The suggested solutions included controlling the source of vibration (in Case 5) and simple alterations of the floor of the portable classroom to change the mass and the frequency of vibration (in Case 6). The paper also summarizes (1) sources of vibrations that may affect structures, a brief overview of the damaging effects of each vibration type, and methods to mitigate these effects; and (2) general information on the frequency contents of vibrations from human activities and the threshold levels for structures of different construction types and usage, including those supporting sensitive equipment.