Floor vibration evaluations for medical facilities
Transcript of Floor vibration evaluations for medical facilities
Floor vibration evaluations for medical facilities
Chad Himmel, PEChad Himmel, PEAssociate Engineer, Associate Engineer, JEAJEACOUSTICSCOUSTICS
EENGINEEREDNGINEERED VVIBRATIONIBRATION AACOUSTIC &COUSTIC & NNOISEOISE SSOLUTIONSOLUTIONS
Structural Vibration Disturbance
• Vibrating, rotating building systems equipment• Indoor foot traffic• Occupant activity• Occupant equipment• Vehicle traffic (speed bumps)• Building wind loads
Equipment causing structural vibration disturbance
• Centrifuges & shakers• Freezer & refrigerator
compressors• Glasswash & sterilization
equipment• MEP, HVAC and central
plant equipment– Fans– Chillers & pumps– Transformers
Structural Vibration Sensitivity
• Offices, patient rooms, meeting rooms, lecture halls• Operating rooms
and equipment
• Microscopes• Radiological imaging & research equipment• Magnetic resonance imaging equipment• Nanoscale research imaging equipment
Generic Criteria
• Colin G. Gordon, “Generic Criteria for Vibration-Sensitive Equipment”, Proceedings ofInternational Society for Optical Engineering (SPIE), Vol. 1619, San Jose, CA, November 4-6, 1991, pp. 71-85
Case #1Eye Clinic - Laser Surgery Room
• New construction• Pier & beam system• W12x22 beams• Steel channel joists @
24” o.c.• Plywood subfloor• “Bouncy”
Case #2Biomedical Research Facility
• Space planning• New building with
structure identical to existing building
• NMR spectroscopy equipment planned
• Centrifuges, shakers & ambient vibration
• Lab users reported occasional “streaks” in spectrometer imaging, but mostly “okay” performance
VC-C (approximated)
Mfr. Criteria
Case #3 - Proposed MRI Suite
• New platform above existing slab is proposed
• Platform stiffness can be “made to order”
• Existing floor slab cannot support weight of proposed MRI equipment
• Occupied space below precludes structural reinforcement from below
MRI #1 MRI #2Control Rooms
#1 #2
Structural FloorMRI Platform
Structure (above)
Pre-Design Evaluation Measurements
• Ambient vibration measurements on existing suspended structural floor slab:– 3 mutually perpendicular axes (X, Y & Z)– Narrow band (1/8 – 1.5 Hz)– 1/3 octave band– Long duration (3 minutes)
• Structural response to heel drop impact to determine apparent structural resonant frequency– Vertical axis only– Narrow band (1/8 – 1.5 Hz)– Short duration (10 seconds)
Existing ConditionAmbient Measurement Results
• Peak disturbance frequencies: 9.5, 15, 19, 23-24 and 29 Hz• Disturbance correlates with 19 Hz apparent resonance
Vibration Control Recommendations
Plan Section
• Control room bay dissimilar to magnet bay– Internal de-tuning to reduce operator disturbance
• Very stiff perimeter elements and beams– Minimize deflection and platform shape distortion
Noise Control Recommendations
• Partition Design– Perimeter framing decoupled from platform slab– Internal partitions not tied to building structure
Structural Design Implementation
• Structural engineer performed Murray “walker” analysis and dynamic analysis to confirm resonant frequency
• Joist spacing (MRI Rooms ≠ Control Rooms) and edge stiffening
Post-Construction Measurements
• Intent: confirm compliance with criteria• Scheduled before facility occupation and
equipment installation to allow for corrections, if necessary
• With unloaded, undamped floor• With weight-loaded simulation--weights stacked
on floor at magnet location
Vibration Measurement Results
• Amplitude was not reduced
• Peaks were shifted to meet specific criteria
Post-Occupancy Evaluation
• Equipmentmanufacturers’commissioning– vibration– noise
• Users’ evaluation– image quality– noise & vibration
Acknowledgements
• Baylor College of Medicine– Human Neuroimaging Lab: Read Montague– Facilities Design & Construction: Philip Dee
• Page Southerland Page, Architects: Scott Tucker, AIA
• OmniPLAN Architects: Key Kolb, AIA
• Walter P. Moore, Structural Engineers: Ram Gupta, PE
• Atkinson Engineering: Tim Atkinson, PE
• Siemens Medical Systems: David Draeger
• JEAcoustics: Jack Evans, PE and Daniel Kupersztoch