Vibration testing and evaluation for source detection of bothersome structural vibrations

Matthew A Pavelchak

doi:10.1051/matecconf/20152402006

Abstract

Buildings are subjected to a myriad of vibration excitation sources including mechanical systems, human activity, vehicular traffic, and other environmental conditions. The characteristics (amplitude and frequency) of the excitation from these sources can vary significantly overtime as building use patterns change, systems age, and maintenance activities vary. Overtime many building owners/operators find themselves dealing with vibration complaints which arise unexpectedly and without obvious cause. The complexity of many modern facilities can make pinpointing the source of bothersome vibrations equivalent to finding a needle in a haystack. The objective of this paper is to explore the process of vibration source detection in complex existing facilities through three recent case studies. The vibration testing and evaluation methodologies utilized for source detection on these case studies is explored to highlight challenges faced on these types of projects. Each of the case studies involve existing buildings with many years of successful operation before bothersome vibration events were reported. The case studies presented, explore complaints related to sensitive medical equipment as well as human perception of vibrations.

Highlights

Vibration concerns related to sensitive equipment and human perception often develop in existing facilities without an obvious identifiable cause after many years of acceptable performance
After review of the ambient structural vibrations it was determined that the microscopes vibration criteria were best represented by the Class A criteria (2,000 Micro Inches Per Second - MIPS) presented in the American Institute of Steel Construction (AISC) Design Guide 11 (DG11)
This testing did produce some vibration events close to the limits for human perception of vibrations from AISC DG11; the durations produced were inconsistent with the complaints

Summary

Introduction

Vibration concerns related to sensitive equipment and human perception often develop in existing facilities without an obvious identifiable cause after many years of acceptable performance. A high-rise hospital in Houston, Texas, USA began to receive complaints from surgeons regarding floor mounted microscopes in the neurosurgery operating suites. The management of a high-rise commercial office building in Omaha, Nebraska, USA began receiving complaints of perceptible vibration events in an isolated area of Level 12. The complaints described intermittent vibration events of varying duration from 5 minutes to 1 hour. Several tenants within a low-rise hospital building began to complain of intermittent perceptible vibration events within their workspaces. Over the course of many months the complaining staff maintained vibration event logs. Review of this data indicated that while the events were seemingly random a greater density of events occurred in the early morning and in the middle of the afternoon. During active periods as many as 25 events would be reported within an hour

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Conclusion