2009 seismic design for cooling towers

CTI Sponsored Educational Program Seismic Design Requirements for Cooling Towers2009 AHR Expo - Chicago

January 26, 2009

Slide No.: 1

CTI Sponsored Educational Program

Presented By:Panos G. Papavizas, P.E.

Baltimore Aircoil Company


January 26, 2009

Slide No.: 2

CTI Mission Statement

To advocate and promote the use of environmentally responsible Evaporative Heat Transfer Systems (EHTS) for the benefit of the

public by encouraging:� Education� Research� Standards Development and Verification� Government Relations� Technical Information Exchange


January 26, 2009

Slide No.: 3

CTI Objectives

� Maintain and expand a broad base membership of individuals and organizations interested in Evaporative Heat Transfer Systems (EHTS).� Owner/Operators� Manufacturers� Suppliers

� Identify and address emerging and evolving issues concerning EHTS.

� Encourage and support educational programs in various formats to enhance the capabilities and competence of the industry to realize the maximum benefit of EHTS.


January 26, 2009

Slide No.: 4

CTI Objectives

� Encourage and support cooperative research to improve EHTS technology and efficiency for the long-term benefit of the environment.

� Assure acceptable minimum quality levels and performance of EHTS and their components by establishing standard specifications, guidelines, and certification programs.

� Establish standard testing and performance analysis systems and procedures for EHTS.

� Communicate with and influence governmental responsible technologies, benefits, and issues associated with EHTS.

� Encourage and support forums and methods for exchanging technical information on EHTS.


January 26, 2009

Slide No.: 5

CTI Certification Program

� STD-201� The standard sets forth a program whereby the Cooling

Technology Institute will certify that all models of a line of evaporative heat rejection equipment offered for sale by a specific Manufacturer will perform thermally in accordance with the Manufacturer’s published ratings.

� Applies to Mechanical Draft Evaporative Heat Rejection Equipment such as Cooling Towers, Closed Circuit Coolers (and Evaporative Refrigerant Condensers).


January 26, 2009

Slide No.: 6

Please visit our website atwww.cti.org


January 26, 2009

Slide No.: 7

Publication and Presentation Disclaimer 2009

The information contained in the following publication, paper or presentation is intended for education by the author or presenter, however information

given is in no way an endorsement of the Cooling Technology Institute. The publication, paper or presentation has been reviewed by the CTI staff and program committee for commercial content, however there

may be differing opinions regarding the content of information. The Cooling Technology Institute accepts no liability for its content.


January 26, 2009

Slide No.: 8

Seismic Design Requirements for Cooling Towers

National Seismic Hazard MapSource: http://earthquake.usgs.gov/research/topics.php?areaID=7


January 26, 2009

Slide No.: 9

Overview

� Key Determinants of Seismic Design Requirements

� Seismic Design and Qualification Requirements

� Qualification by Shake-Table Testing� Functional Qualification Considerations� Functional Verification Methodology� Seismic Certification Requirements


January 26, 2009

Slide No.: 10

Overview

� Evidence of Compliance� System Considerations� Summary


January 26, 2009

Slide No.: 11

� Building code� Seismic design classification� Level of earthquake safety

Key Determinants of Seismic Design Requirements


January 26, 2009

Slide No.: 12

Building Codes - Nationwide

Source: http://www.iccsafe.org/government/adoption.html


January 26, 2009

Slide No.: 13




January 26, 2009

Slide No.: 14




January 26, 2009

Slide No.: 15

� California Code of Regulations, Title 24

� Part 2 known as California Building Code

� 2 volumes

� Effective 1/1/2008

Building Code - California


January 26, 2009

Slide No.: 16

� 2007 CBC incorporates by adoption the 2006 IBC

� CA amendments in italics

� Agency adoption tables in each Chapter

Building Code - California


January 26, 2009

Slide No.: 17

Seismic Design Provisions of 2006 IBC��

Every structure and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake ground motions in accordance with ASCE 7…

Seismic provisions in 2006 IBC based on

ASCE/SEI 7-05


January 26, 2009

Slide No.: 18

Seismic Design Classification

� Cooling towers can be treated as either:� Nonstructural components of buildings� Nonbuilding structures

� Classification dependent on size and application


January 26, 2009

Slide No.: 19

Seismic Design Classification

Factory assembled towers

treated as Nonstructural Components

Field erected towers treated as

NonbuildingStructures


January 26, 2009

Slide No.: 20

Level of Earthquake Safety

� Presentation focus – factory assembled towers treated as nonstructural components

� Two basic levels of safety for towers treated as nonstructural components:� Life safety (i.e., position retention)� Post-earthquake functionality


January 26, 2009

Slide No.: 21

Position Retention

� Intent – reduce hazard to life resulting from equipment sliding, toppling, or falling

� Focus on supports & attachments

SupportsAttachments


January 26, 2009

Slide No.: 22

Position Retention

� Design of tower structure for seismic forces may be required

� Typical basis of qualification is analysis


January 26, 2009

Slide No.: 23

� Critical applications where towers serve a vital function� Emergency

response centers� Hospitals, etc.

� Towers classified as designated seismic systemcomponents

Post-Earthquake Functionality


January 26, 2009

Slide No.: 24

� Intent – achieve high probability that towers will perform their intended function following an earthquake

� Focus on supports, attachments, and towers Supports, Attachments

and Towers



January 26, 2009

Slide No.: 25

� Design for 50% higher forces than those required for position retention

� Design for higher seismic forces:� Directly affects tower

structural stability and integrity

� Functional reliability impacted only indirectly



January 26, 2009

Slide No.: 26

Seismic Design and Qualification Requirements of ASCE 7-05

� Applicable Chapter and Scope� Key Variables � Exemptions� General Requirements� Special Requirements� Methods of Seismic Qualification


January 26, 2009

Slide No.: 27

Applicable Chapter and Scope

��

��

��

��

��

�� This Chapter establishes minimum design criteria for nonstructural components that are permanently attached to structures and for their supports and attachments…


January 26, 2009

Slide No.: 28

Key Variables

� Key variables that establish specific seismic design and qualification requirements for towers:� Seismic Design Category (SDC)� Component importance factor (Ip)� Design spectral acceleration at short period

(SDS)� Tower attachment location in a structure

� Unique for each project� Should be provided in the tower spec


January 26, 2009

Slide No.: 29

Seismic Design Category

Seismic Design Category (SDC): A to F

(ASCE 7 Section 11.6; IBC Section 1613.5.6)

Occupancy Category: I to IV(ASCE 7 Table 1-1; IBC

Table 1604.5)

Design acceleration: SDS and SD1

(ASCE 7 Section 11.4; IBC Section 1613.5)

Cooling Tower SDC

Building


January 26, 2009

Slide No.: 30

Component Importance Factor

� Ip = 1.5� Component required to function (i.e., post-

earthquake functionality)� Component failure could impair operation of

facility� Designated seismic system component

� Ip = 1.0� All other towers (i.e., position retention)


January 26, 2009

Slide No.: 31

Design Spectral Acceleration (SDS)

� Design acceleration that cooling towers are proportioned to resist

� Dependent on site soil properties and mapped spectral acceleration

� 2/3 of the Maximum Considered Earthquake (MCE) spectral acceleration

� Expressed in g’s


January 26, 2009

Slide No.: 32

Mapped Spectral Accelerations

Source: http://earthquake.usgs.gov/research/hazmaps/pdfs/


January 26, 2009

Slide No.: 33

Mapped Spectral Accelerations

Source: http://earthquake.usgs.gov/research/hazmaps/pdfs/


January 26, 2009

Slide No.: 34


Source: http://earthquake.usgs.gov/research/hazmaps/design/


January 26, 2009

Slide No.: 35




January 26, 2009

Slide No.: 36




January 26, 2009

Slide No.: 37




January 26, 2009

Slide No.: 38

Tower Attachment Location� Seismic acceleration

amplified at point of tower attachment with respect to base

Transamerica Building, San Francisco, CASource: http://pubs.usgs.gov/fs/2003/fs017-03/

(Eq. 13.3-1)


January 26, 2009

Slide No.: 39

Component Seismic Design Force

0.4SDS – design ground acceleration

(1 + 2z/h) – height amplification

ap – component amplification

Rp/Ip – adjusted energy dissipation capability

Wp – component weightProduct is design

acceleration at attachment point

ap = 1.0 rigid, 2.5 flexible


January 26, 2009

Slide No.: 40

Exemptions

� Towers that meet the following conditions are exempt from seismic design requirements:� All towers in SDC A and B� Towers in SDC C provided Ip is equal to 1.0


January 26, 2009

Slide No.: 41

General Requirements

� All non-exempt towers must meet the requirements of Section 13.2.1

� Section can be satisfied by� Project specific design and documentation� Manufacturer’s certification of seismic

qualification based on analysis, testing, or experience data


January 26, 2009

Slide No.: 42

��

�� !� " ��#$!�% &�'�(��!��$� )�� &!� �

&*�� !� ��% �&&�')��$��')� &*�� % &�'�

Architectural, mechanical, and electrical components, supports, and attachments shall comply with the sections referenced in Table 13.2-1. These requirements shall be satisfied by one of the following methods:

1. Project-specific design and documentation prepared and submitted by a registered design professional.

2. Submittal of the manufacturer’s certification that the component is seismically qualified by

a. Analysis.

b. Testing in accordance with the alternative set forth in Section 13.2.5.

c. Experience data in accordance with the alternative set forth in Section 13.2.6.

General Requirements


January 26, 2009

Slide No.: 43

Special Requirements – ASCE 7

� Special certification required for towers that must remain operable following an earthquake

� Requirements contained in Section 13.2.2a� Certification must be based on

� Shake table testing� Experience data


January 26, 2009

Slide No.: 44


��! ��!(!� �!�&��#$!�% &�'�(��'!+& �*�

�!'% !��,'�% '� Certifications shall be provided for designated seismic systems assigned to Seismic Design Categories C through F as follows:

a. Active mechanical and electrical equipment that must remain operable following the design earthquake shall be certified by the supplier as operable based on approved shake table testing in accordance with Section 13.2.5 or experience data in accordance with Section 13.2.6. Evidence demonstrating compliance of this requirement shall be submitted to the authority having jurisdiction after review and approval by the registered design professional.


January 26, 2009

Slide No.: 45


� Limits qualification methods for “active”equipment (i.e., equipment with moving or rotating parts)

� Recognized by the code writing community that it is impractical and often inadequate to verify functionality by analytical means


January 26, 2009

Slide No.: 46

Special Requirements – 2006 IBC

� Requirements for designated seismic system components contained in Sections 1708.2 and 1708.5

� Qualification can be based on� Shake table test� Three dimensional shock tests� Analytical method� Experience data� Rigorous analysis providing equivalent safety


January 26, 2009

Slide No.: 47


�-./��'�!&+�(��'!'% !��'!'� &�� The tests specified in Sections 1708.3 through 1708.6 are required for the following:

1. The seismic-force-resisting systems in structures assigned to Seismic Design Category C, D, E or F, as determined in Section 1613.

2. Designated seismic systems in structures assigned to Seismic Design Category D, E or F.

3. Architectural, mechanical and electrical components in structures assigned to Seismic Design Category C, D, E or F that are required in Section 1708.5.


January 26, 2009

Slide No.: 48


�-./�0��!'% !��#$ !(!� �!�&��(�% �� &!� � &*� ��!� �

#$!% &�� The registered design professional in responsible charge shall state the applicable seismic qualification requirements for designated seismic systems on the construction documents. Each manufacturer of designated seismic system components shall test or analyze the component and its mounting system or anchorage and submit a certificate of compliance for review and acceptance by the registered designprofessional in responsible charge of the design of the designated seismic system and for approval by the building official. Qualification shall be by an actual test on a shake table, by three-dimensional shock tests, by an analytical method using dynamic characteristics and forces, by the use of experience data (i.e., historical data demonstrating acceptable seismic performance) or by a more rigorous analysis providing for equivalent safety.


January 26, 2009

Slide No.: 49


� IBC Section 1708.5 and Section 13.2.2a of ASCE 7 appear to be in conflict

� Acceptable methods of seismic qualification dependent on code interpretation

� Proposals to clarify the code are in process


January 26, 2009

Slide No.: 50

Summary of Requirements

Ip = 1.5Ip = 1.0Seismic DesignCategory

Applicable Methods of Seismic Qualification forCooling Towers

A and B Exempt Exempt

C ExemptAnalysis?Testing

Experience Data

D, E, and FAnalysis Testing

Experience Data

Analysis?Testing

Experience Data


January 26, 2009

Slide No.: 51

Methods of Seismic Qualification

� �& ,'!'– Analysis of tower under code-prescribed seismic design forces. Typically, analysis focused only on anchorage and main structural components

� �'�!&+ – Full-scale shake table testing in accordance with ICC-ES AC 156, “Acceptance Criteria for Seismic Qualification by Shake-Table Testing of Nonstructural Components and Systems” (ASCE 7 Section 13.2.5)

� �1�!&�� – Seismic suitability determined using actual earthquake performance data collected in accordance with a nationally recognized procedure (ASCE 7 Section 13.2.6)


January 26, 2009

Slide No.: 52

Qualification by Experience Data

� Limitations:� Difficulty of establishing the actual seismic

demand in building applications� Low probability of data being applicable to current

generation of products� Infrequency of strong motion earthquakes� Lack of a nationally recognized procedure for

data collection and application

Use of experience data for seismic qualification currently not viable


January 26, 2009

Slide No.: 53

Qualification by Shake-Table Testing

� Shake-table testing most reliable method for functional qualification of cooling towers� Physical testing of entire unit� Severe test� Standardized test methodology� Test methodology consistent with current

code requirements


January 26, 2009

Slide No.: 54


� Not always the case� Qualification by shake-table testing for

building applications first appeared in the 1985 edition of the NEHRP provisions

� Not used to any significant extent for mechanical equipment outside the nuclear industry


January 26, 2009

Slide No.: 55


� Not always the case� No recognized test methodology suitable for

nonstructural building components until 2000

� Tests conducted prior to 2000 hampered by inconsistent interpretation of building code requirements


January 26, 2009

Slide No.: 56


� AC156 first issued in 2000� Developed by Schneider

Electric, Building Seismic Safety Council, and ICBO Evaluation Service.

� Now maintained by ICC-ES, Inc.

� Most recent edition effective January 1, 2007


January 26, 2009

Slide No.: 57


� Suitable for qualification in accordance with 1997 UBC and 2006 IBC.

� Referenced in ASCE 7-05 and 2003 NEHRP provisions

� Applicable to all types of equipment


January 26, 2009

Slide No.: 58

Functional Verification Requirements of AC156

4.4 Functional and Operability Requirements: A listing and detailed description shall be provided of the functional and operability equipment requirements and/or tests used to verify pre- and post-seismic-testing functional compliance.


January 26, 2009

Slide No.: 59

Functional Verification Requirements of AC156

� AC156 does not define specific functional verification requirements

� Manufacturer must define:� Functional characteristics of equipment� Specific pre- and post-seismic test

functional verification tests and activities


January 26, 2009

Slide No.: 60

AC156 Acceptance Criteria for Functional Verification

6.7.2 Components with Ip = 1.5: The equipment is deemed to be essential to the continued operation of a facility, and/or essential to maintaining critical life support systems, and/or contains materials deemed to be hazardous, to humans or the environment, in quantities greater than the exempted amounts listed in the code. After completion of the seismic testing, the UUT shall satisfy the functional and operational requirements and/or tests specified in Section 4.4, with equivalent results to those of the pre-test functional compliance testing of Section 6.3.

Post-test functionality � Pre-test functionality


January 26, 2009

Slide No.: 61

Functional Characteristics of Cooling Towers

� Reject waste heat by evaporative cooling

� Accomplished through interaction of tower sub-systems

Open

Closed Circuit


January 26, 2009

Slide No.: 62


� Sub-systems:� Air moving system� Water distribution

system� Heat transfer

system� Structural system

Open

ClosedCircuit


January 26, 2009

Slide No.: 63


� Sub-systems must remain largely intact after an earthquake for towers to perform their intended function

Open

Closed Circuit


January 26, 2009

Slide No.: 64

Functional Verification of Cooling Towers

� Integrity of sub-systems must be verified to assure functionality

� Conduct thermal performance tests before and after shake-table testing?� AC156 requires equivalent pre- and post-

test functionality� Establishing absolute thermal capability for

seismic qualification is unnecessary


January 26, 2009

Slide No.: 65

Functional Verification Methodology

� Comprehensive test and inspection program that focuses on all tower sub-systems

� Tests and inspections must verify:� Air moving system is substantially intact and

delivers equivalent air flow� Mechanical system is not compromised and

can be operated safely


January 26, 2009

Slide No.: 66


� Tests and inspections must verify:� Water distribution system delivers

equivalent water flow without significant leaks

� Heat transfer system is not structurally or thermally compromised

� Structural system is substantially intact with only minor yielding or distortion that does not affect functionality


January 26, 2009

Slide No.: 67


� Conduct production-type tests before and after shake-table testing to demonstrate equivalent:� Fan/motor performance� Water distribution� Leak tightness� Vibration levels


January 26, 2009

Slide No.: 68

� Define all functional verification tests and inspections in the seismic test plan

� Conduct functional verification activities and thorough inspections at shake-table test facility



January 26, 2009

Slide No.: 69

� Document all before and after test and inspection results



January 26, 2009

Slide No.: 70



January 26, 2009

Slide No.: 71

Seismic Certification

� Critical towers qualified by shake-table testing must be certified as operable by the manufacturer

� No specific guidelines in the code for preparing certificate of compliance


January 26, 2009

Slide No.: 72


� Recommended to include the following:� Name of the manufacturer� Product line covered by the certificate� The building code (e.g., 2006 IBC)� Reference to AC156 as the test protocol� Performance level (i.e., Ip = 1.5 for critical

towers)


January 26, 2009

Slide No.: 73


� Recommended to include the following:� Certified design seismic force coefficient,

Fp/Wp

� Certified SDS (design spectral acceleration parameter at short period) level

� Installation restrictions, if any� Product restrictions, if any


January 26, 2009

Slide No.: 74

Evidence of Compliance� Certificate of compliance

may not be sufficient in itself as evidence of testing and seismic qualification

� All documentation (i.e., test plan, lab test report, calculations, etc.) must be available for review and approval


January 26, 2009

Slide No.: 75

Functionality

Non-structuralintegrity

Structural integrity

Anchorageintegrity

ExperienceData

TestingAnalysisMethod

Characteristic

Suitability of Qualification Methods for Cooling Towers


January 26, 2009

Slide No.: 76

System Considerations

� Qualification of towers alone does little to assure functionality of critical systems

� All components within critical systems must receive equivalent attention


January 26, 2009

Slide No.: 77

System Considerations

� System qualification is best directed by the responsible design professional


January 26, 2009

Slide No.: 78

Summary

� The key determinants of seismic design requirements for cooling towers are � Building code� Seismic design classification� Level of earthquake safety.

� The seismic design provisions for cooling towers are contained in ASCE/SEI 7.


January 26, 2009

Slide No.: 79

Summary

� The key variables that establish seismic requirements for towers are � Seismic design category� Component importance factor� Design spectral acceleration at short period� Tower attachment location.

� The methods of special seismic certification for active equipment are limited to testing and experience data in ASCE 7.


January 26, 2009

Slide No.: 80

Summary

� The use of experience data is currently not a viable method of seismic qualification.

� The most reliable method of assuring cooling tower functionality is shake-table testing in accordance with ICC-ES AC156.

� Seismic qualification programs for towers must consider their unique functional characteristics.


January 26, 2009

Slide No.: 81

Summary

� The integrity of tower sub-systems must be verified to assure functionality.

� All components within critical systems must receive equivalent attention.


January 26, 2009

Slide No.: 82

Questions

2009 seismic design for cooling towers

Documents

cooling technology institute

registered design professional

nationally recognized procedure

seismic design category

seismic design requirements

designated seismic systems

design acceleration

position retention