the day the earth shook: controlling construction-induced

I2SL Annual ConferenceOctober 21-23, 2019

Denver, Colorado

The Day the Earth Shook: Controlling Construction-Induced Vibrations in Sensitive Occupancies

Presented by:

Michael J. Wesolowsky, Ph.D., P.Eng.Associate Principal

Swallow Acoustic Consultants Ltd. /

Thornton Tomasetti

366 Revus Ave., Unit 23 Mississauga, ON, Canada, L5G [email protected]


Denver, Colorado

Learning Objectives• Understand how vibration criteria for sensitive laboratory and research equipment can

often drive the design and operation of laboratory buildings;

• Identify where a construction vibration assessment is necessary to ensure sustainable operation of an existing laboratory building;

• Understand the cost and operational implications of renovations and additions to laboratory and research facilities; and

• Learn where manufacturer-provided vibration specifications may potentially be treated with some skepticism as they may not represent the actual vibration limit required for successful operation of the sensitive equipment.


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Case Study #1

Introduction Vibration Criteria

Case Study #2 Case Study #3

Summary

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Introduction

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So What’s the Story?

• Our firm has been involved in several projects over the years which involve the control of construction-induced vibrations

• Many are straightforward, based on municipal regulation• And best practice

• With increasingly vibration-sensitive equipment:• Often difficult to obtain vibration criteria• Often difficult to predict source levels

• How do we develop a plan to address these issues?

Introduction

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Vibration Criteria

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How do we Define Vibration Criteria (VC)?• Traditionally, over the past 25 years vibration criteria for sensitive equipment was

given as the so-called ‘VC-Curves’ • Vibration Criteria Curves

• Provide frequency-dependent root mean square (rms) levels of velocity, grouped in 1/3 octave bands

Vibration Criteria

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VC-Criteria

Imperceptible

Perceptible

Vibration Criteria

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Vibration Criteria

Curve

Max Velocity

Amplitude1

mm/s (min/s)

Description of Use

Achievable

Magnification

Factor2

Workshop (ISO) 800 (32,000) Distinctly perceptible vibration. Appropriate to workshops and non-sensitive areas -

Office (ISO) 400 (16,000) Perceptible vibration. Appropriate to offices and non-sensitive areas. -

Residential Day (ISO) 200 (8,000)Barely perceptible vibration. Maximum recommended for general sleep areas. Usually adequate

for computer equipment.40x

Residential Night (ISO) 140 (5,600) Appropriate for most sleep areas such as hospital recovery rooms. -

Operating Theatre (ISO) 100 (4,000)Threshold of perceptible vibration. Suitable in most instances for surgical suites, catheterization

procedures, and for other equipment of low sensitivity. Suitable for very sensitive sleep areas.100x

VC-A 50 (2,000)Adequate in most instances for microbalances and optical balances. Also suitable for most

vivaria.400x

VC-B 25 (1,000) Micro-surgery, eye surgery and neurosurgery, CT, CAT, PET, fMRI, SPECT, DOT, EROS. 750x

VC-C 12.5 (500)Appropriate for many MRIs, NMRs, and moderately sensitive electron microscopes to 1 mm detail

size.1000x

VC-D 6.25 (250)Suitable in most instances for demanding equipment, many MRIs, electron microscopes (SEMs

and TEMs) to 0.3 mm, and E-Beam systems.30,000x

VC-E 3.12 (125)

A challenging criterion to achieve. Assumed to be adequate for the most demanding of sensitive

systems including long path, laser-based, small target systems, systems working at nanometer

scales and other systems requiring extraordinary dynamic stability.

-

VC-F 1.56 (62.5)Appropriate for extremely quiet research spaces. Generally difficult to achieve in most instances.

Not recommended for use as a design criterion, only for evaluation.-

VC-G 0.78 (31.3)Appropriate for extremely quiet research spaces. Generally difficult to achieve in most instances.

Not recommended for use as a design criterion, only for evaluation.-

Notes: 1. As measured in one-third octave bands of frequency over the frequency range 8 to 80 Hz (Workshop through VC-B), or

1 to 80 Hz (VC-C through VC-G).

2. Approximate magnification factor achievable for optical microscopes.

Vibration Criteria

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However…• In the past few years, imaging equipment has been improving

• higher resolution = higher vibration sensitivity

• Generic VC-Criteria provides a GENERAL design guideline, but is no longer considered absolute

• It is common for manufacturers to provide their own criteria• often require proof of performance investigation

Vibration Criteria

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Case Study #1

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Existing Hospital in Toronto• Original 110-bed patient tower constructed in 1929• New addition / building built approximately every decade since

• Frankenstein Hospital!• Major 550,000 sf redevelopment announced:

• Replacement of the oldest beds • Replacement of the mental health inpatient units• Consolidation of ambulatory care and ambulatory procedures• Creation of two levels of underground parking and a new main entrance• Accommodation of other administrative and support services needed to support the

clinical services

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Construction Vibration


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So What’s the Problem?• The construction will be phased over several years• Existing hospital operations cannot be compromised• Several sensitive adjacencies to the construction site

• Operating Suites• Diagnostic Imaging• Laboratories

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Operating Suites

Diagnostic Imaging

First to be Demolished

Laboratories

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So What do We do About it?

• SACL hired directly by hospital to conduct an initial series of tests• Backhoe used in the parking lot to determine vibration transfer to the DI areas

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Backhoe

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Backhoe

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Criterion

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What we Found


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What we Found

Criterion

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What we Found

Criterion

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What we Found

Criterion

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And how did the Hospital React?• Mass panic• Commissioned a larger scale testing scheme to determine building response to a wide

range of construction activities:• Excavator• Caisson Driller• Vibratory Compactor

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Data Analysis• Based on the measured source levels and site-specific attenuation, we estimated the

expected vibration caused by:• Phase 1: Demolition of the E Wing and F Podium• Phase 2: Construction of the new tower• Phase 3: Renovation of the F and D wings• Phase 4: Demolition of the A, B, C, D podium and F wings

• Developed “Zones of Influence” throughout the site due to each activity

• FEM models of the building were also used to determine expected attenuation


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As a Result…• Specifications were developed so that design/construction team could properly bid

on/cost the project• Consideration has been given for moving DI to temporary area


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Case Study #2

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Existing Hospital in Southwestern Ontario, Canada• Original hospital constructed in the 1950s• On the northwest corner of the current location, they are building a three storey tower

to house:• A new Emergency Department• Surgical Suites• Medical Devices Reprocessing Department• Permanent home for the Mental Health and Addiction Services Unit


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So What’s the Problem?• The construction will be directly adjacent to the existing diagnostic imaging and nuclear

camera suites• Underpinning directly under the CT room


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Addition

CT Scanner Nuclear Cameras


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So What do We do About it?• SACL hired to conduct a series of tests

• Backhoe used in the parking lot to determine vibration transfer to the DI area


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Background Vibrations

Criterion


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Backhoe-Induced Vibrations

Criterion


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And Then What?• Specifications were developed so that the construction team could properly bid on/cost

the project• Procured mobile CT in a trailer during main construction

• At a cost of $500,000!

• Monitoring plan developed to determine the vibrations in the original DI area• Intention was to operate CT scanner in original location once vibrations were

considered acceptable

• BUT…


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And Then What?• Measurements showed consistent and excessive exceedance of criterion


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And Then What?


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Typical Weeks of Monitoring


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Liability Disaster?• Hospital test-operated the existing CT scanner during construction, and found NO issues

with imaging quality• After 7 months of monitoring, program discontinued, mobile CT removed, full operation

of existing CT scanner resumed• Over our objections!

• Are the manufacturer criteria significantly over-conservative?


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Case Study #3

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• University hospital

• Renovation activities:

• Partition demolition

• Slab cutting

• Elevator installation

• Construction hoist

• Clinical laboratory and diagnostic imaging equipment

Biomerieux VITEK MS Mass Spectrometer


Existing Hospital in Chicago

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BASEMENT LEVEL


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BASEMENT LEVEL


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BASEMENT LEVEL


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PREDICTIVE VIBRATION CONTOUR MAPS


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PREDICTIVE VIBRATION CONTOUR MAPS


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Construction Vibration Control Methods

COMBINATION OF ALL OF THESE OPTIONS

EQUIPMENT RELOCATION

•ONLY FEASIBLE FOR SMALL EQUIPMENT

•COULD IMPACT WORKFLOW

ISOLATION TABLES/MOUNTS

•DEPENDENT ON EXCITATION FREQUENCIES

•MANUFACTURER RESTRICTIONS

ACTIVITY SCHEDULING

•ECONOMICAL

•FEASIBLE FOR SHORT TERM ACTIVITIES

DIFFERENT CONSTRUCTION

TECHNIQUE

•OPT FOR LESS DISRUPTIVE METHODS


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1. Construction vibration can have significant impact on existing facilities with vibration-sensitive occupancies

2. Extensive vibration testing may be necessary to determine extent of “Zone of Influence” and possible mitigation measures

3. Monitoring is often necessary during construction to ensure safe operation of vibration-sensitive equipment

4. Are manufacturer vibration criteria realistic??

What Did We Learn?

Concluding Comments

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Swallow Acoustic Consultants Ltd. /

Thornton Tomasetti

Questions ?

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the day the earth shook: controlling construction-induced

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