Baltimore Aircoil Company

Now AvailableON SERIES 3000 ANDPT2 COOLING TOWERS

IBC Compliance for Seismic and Wind

Manufacturers must provide certification to confirm that their towers have beenqualified by at least one of the following methods:

Testing – A full-scale cooling tower is subjected to a simulated seismic event in a testlaboratory.Typically, the test method is a shake-table test conducted in accordance witha code-recognized test procedure, such as the AC156.

Analysis – A cooling tower is analyzed to determine if it can resist the code-prescribed,seismic design forces.Typically, an analysis of this type focuses on the anchorage only oron the anchorage and main structural components.The analysis usually does not addressthe non-structural portions of a tower that affect functionality and cannot be used forcooling towers with an importance factor of 1.5.

Experience Data – A cooling tower is qualified using actual earthquake performancedata collected in accordance with a nationally recognized procedure.Though this methodis used to some extent in the nuclear power industry, its use in commercial mechanicalequipment applications is extremely limited.

The methods are not equally suitable for verification of all aspects of cooling towerseismic performance.The suitability of each method is summarized in the following table.

QUALIFICATION METHODS

Suitability of Qualification Methods for Cooling Towers

Characteristic

Anchorage integrity

Structural integrity

Non-structuralcomponent integrity

Functionality

Qualification Method

Anaylsis

4 4

44

4

4

Testing Experience Data

What is the International Building Code®?The International Building Code® (IBC) is a model code developed by the InternationalCode Council (ICC)® and available for adoption by jurisdictions internationally.Variouseditions of the IBC are the basis for nearly all US state and local building codes. Onceadopted, the IBC provisions become enforceable regulations.

The IBC includes structural design requirements for buildings and structures. Coolingtowers are parts of buildings and other structure types, and as such, the structuraldesign falls within the scope of the IBC.The design provisions contain requirementsfor towers subjected to wind and seismic loads. For these design requirements, theIBC refers extensively to ASCE/SEI 7, the consensus standard published by theAmerican Society of Civil Engineers.

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Several key variables are provided in the project design documents to determine theseismic design requirements for factory assembled cooling towers.

Seismic Design Category (SDC) – A building classification ranging from A to F (low to high) that is based on the Occupancy Category and the severity of the designground motion at a building site.

Occupancy Category – A classification ranging from I to IV for buildings and otherstructures based on the level of occupancy and the nature of use. Category I buildingsrepresent a low hazard to life in the event of failure. Category IV buildings are considered essential facilities and include hospitals and emergency response centers.

Component Importance Factor (Ip) – All cooling towers are assigned a component factor of either 1.0 or 1.5. Towers needed for continued operation of anessential facility (Occupancy Category IV), or required to function after an earthquakeare assigned an Ip of 1.5. Air conditioning is needed for operation of most essential facilities, meaning cooling tower operation after an event will be required.

Design Spectral Acceleration (SDS) – The design spectral acceleration is dependenton soil characteristics and maximum ground shaking intensity at a given location. The ground shaking intensity can be obtained from probabilistic seismic hazard mapsprovided in the IBC or by using software tools provided by the ICC® or the U. S.Geological Survey. The specific acceleration that cooling towers are required to resist is the design spectral acceleration at short period, SDS.

Tower Attachment Location – The height of the cooling tower structure within a building affects the design seismic acceleration.

Highest Hazard

64+

48-64

32-48

16-32

8-16

4-8

0-4

Lowest Hazard

%g

Seismic Hazard Map

BAC has developed and implemented a comprehensive approach for qualifying all new products for seismic and wind loads, using multiple methods. BAC’s comprehensive seismic and wind load design and qualificationapproach includes:

Testing:

• Full-size towers are tested at independent test laboratories in accordance with AC156

• Tests are conducted on tri-axial shake tables

•Wind loading tests

• Functional tests are conducted before and after testing to verify functionality and certify towers for use in applications where the component importance factor is 1.5

Analysis:

• Products are analyzed using the latest-generation, three-dimensional finite element analysis (FEA) software packages

•Computer models are validated using full-scale test data as described above

•Computer models are used to optimize tower design for various loading conditions and product configurations

Certification:

• Certificate of Seismic and Wind Compliance provided on every order

• Analysis and testing conducted under the supervision of an independently registered Professional Engineer

QUALIFICATION METHODS BAC’S DESIGN & QUALIFICATION PHILOSOPHY

Baltimore Aircoil CompanyBaltimore Aircoil Company

Reliability:

Insist on shake table

testing based verification

of operability after an

event. According to

ASCE/SEI 7 (American

Society of Civil

Engineers), which is the

basis for much of the

IBC code, analysis only

cannot be used to verify

functionality.

Insist on IBC Compliant Constructionfor your next evaporative cooling equipment project.

Baltimore Aircoil Company

Contact your local BAC Representative for more information

...because temperature matters™

or contact:

Baltimore Aircoil CompanyP.O. Box 7322, Baltimore, MD 21227 USAPhone: 410.799.6200 • Fax: 410.799.6416

Web: www.BaltimoreAircoil.com

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