Regulatory Guide 1.122: Difference between revisions

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{{Adams
{{Adams
| number = ML003739367
| number = ML13350A275
| issue date = 02/28/1978
| issue date = 09/30/1976
| title = Development of Floor Design Response Spectra for Seismic Design of Floor-Supported Equipment or Components
| title = Development of Floor Design Response Spectra for Seismic Design of Floor-Supported Equipment or Components
| author name =  
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/OSD
| addressee name =  
| addressee name =  
| addressee affiliation =  
| addressee affiliation =  
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| license number =  
| license number =  
| contact person =  
| contact person =  
| document report number = RG-1.122, Rev 1
| document report number = RG-1.122
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 4
| page count = 4
}}
}}
{{#Wiki_filter:Revision 1 U.S. NUCLEAR REGULATORY  
{{#Wiki_filter:U.S. NUCLEAR REGULATORY  
COMMISSION  
COMMISSION
February 1978 REGULATORY  
REGULATORY  
GUIDE OFFICE OF STANDARDS  
GUIDE OFFICE OF STANDARDS  
DEVELOPMENT  
DEVELOPMENT
REGULATORY  
REGULATORY  
GUIDE 1.122 DEVELOPMENT  
GUIDE 1.122 DEVELOPMENT  
Line 24: Line 24:
EQUIPMENT  
EQUIPMENT  
OR COMPONENTS
OR COMPONENTS
September
1976


==A. INTRODUCTION==
==A. INTRODUCTION==
Criterion  
Criterion  
2, "Design Bases for Protection Against Natural Phenomena," of Appendix A, "General De sign Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Licensing of Production and Utilization Facilities," requires, in part, that nuclear power-plant structures, systems, and components important to safety be designed to withstand the effects of earth quakes without loss of capability to perform their safety functions.
2, "Design Bases for Protection Against Natural Phenomena," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50,"Licensing of Production and Utilization Facilities," re-quires, in part, that nuclear power plant structures, systems, and components important to safety be de-signed to withstand the effects of earthquakes without loss of capability to perform their safety functions.
 
Para-graph (a)(1) of Section VI, "Application to Engineering Design," of Appendix A, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," to 10 CFR Part 100,"Reactor Site Criteria," requires, in part, that safety-related structures, systems, and components remain functional in the event of a Safe Shutdown Earthquake (SSE). It specifies the use of a suitable dynamic analysis as one method of ensuring that the structures, systems, and components can withstand the seismic loads.Similarly, paragraph (a)(2) of Section VI of the sarkl appendix requires, in part, that the structures, sy.i.ms, and components necessary for continued opezation""th- out undue risk to the health and ie remain functional in the event of an t~qratinrnBasis Earthquake (OBE). Again, the use of suit .d> .amic analysis is specified as one method of ensurt'iAiat the structures, systems, and nents can withstand the seismic loads.* This guide cri e ds acceptable to the NRC* staff for 4 l g tw ori ontal and one vertical floor design .o t various floors or other equip-ment-su locafs of interest from the time-history motions Iting from the dynamic analysis of the supporting cture. These floor design response spectra are needed for the dynamic analysis of the systems or equipment supported at various locations of the sup-porting structure.
 
==B. DISCUSSION==
Nuclear facility structures can be approximated by mathematical models to permit analysis of responses to earthquake motions. Because of the large number of degrees of freedom that would be necessaiy.


Paragraph (a)(1) of Section VI, "Application to Engineering Design," of Appendix A, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," to 10 CFR Part 100, "Reactor Site Criteria," requires, in part, that safety-related struc tures, systems, and components remain functional in the event of a Safe Shutdown Earthquake (SSE). It specifies the use of a suitable dynamic analysis as one method of ensuring that the structures, systems, and components can withstand the seismic loads. Similarly, paragraph (a)(2) of Section VI of the same appendix requires, in part, that the structures, sys tems, and components necessary for continued opera tion without undue risk to the health and safety of the public remain functional in the event of an Operating Basis Earthquake (OBE). Again, the use of suitable dynamic analysis is specified as one method of ensur ing that the structures, systems, and components can withstand the seismic loads. This guide describes methods acceptable to the NRC staff for developing two horizontal and one ver tical floor design response spectra at various floors or other equipment-support locations of interest from the time-history motions resulting from the dynamic analysis of the supporting structure.
and the possible ill-conditioning of the resulting stfqiiess matrix if the complete plant were treated in a cal model, the plant is usually dvided intQ. several separate systems for analysis P.-Urs's-Thus itis usual that there arc one or more matheail models of sup-.,t" I, .= M;porting structures.


These floor de sign response spectra are needed for the dynamic analysis of the systems or equipment supported at various locations of the supporting structure.
Each supporting structure normally supports one or rte systems or of equipment.


The Advisory Committee on Reactor Safeguards has been -consulted concerning this guide and has concurred in ýthe regulatory position.
Also, different m"-.l structure may be required For these reasons, the mathen .Mo A used to generate the seismic excita-tion ..for s ects ent separate analyses of supported.syterZ,_.., -. eq~upment may not be suitable for the*t.Wed-Aoidized analyses of the supporting structure.


==B. DISCUSSION==
I'1ost equipment having a sr'all mass relative to that:of the supporting structure will 'lave negligible interac-tion effects on the support structu, -and will need to be included only in the mass distributicin of the mathemati- cal model for that structure.
Nuclear facility structures can be approximated by mathematical models to permit analysis of responses to earthquake motions. Because of the large number of degrees of freedom that would be necessary and the possible ill-conditioning of the resulting stiffness matrix if the complete plant were treated in a single mathematical model, the plant is usually divided into several separate systems for analysis purposes.


Thus it is usual that there are one or more mathematical models of supporting structures.
For such equipment, a separate analysis will be performed using the floor design response spectra or time-history excitations at the equip-ment-support locations derived from the analysis of the supporting structure.


Each supporting structure normally supports one or more systems or pieces of equipment.
This guide addresses the acceptabil- ity and development of floor design response spectra only. Time-history motions that will give results comparable to the floor design response spectra are also acceptable.


Also, different models of the same structure may be required for different pur poses. For these reasons, the mathematical models used to generate the seismic excitation data for sub sequent separate analyses of supported systems or equipment may not be suitable for the detailed lo calized analyses of the supporting structure.
There are, however, other major equipment systems such as the reactor coolant system whose stiffness, mass, and resulting frequency range should be considered for inclusion in the model of the supporting structure to USNRC REGULATORY
GUIDES Comments should be sent to the Secretary of the Commission.


Most equipment having a small mass relative to that of the supporting structure will have negligible interaction effects on the support structure and will need to be included only in the mass distribution of the mathematical model for that structure.
U.S Nuclear Regulatory Commission.


For such equipment, a separate analysis will be performed using the floor design response spectra or time history excitations at the equipment-support locations
Washington.
*Lines indicate substantive changes from previous issu


====e. USNRC REGULATORY ====
D.C. 2V566. Attention Docketing and Regulatory Guides ate issued to deoctibS and make available to the public Service Section.methods acceptable to the NRC sltal of implemenling specific parts of the Commission aeIgulations.
GUIDES Comments should be sent to the Secretary of the Commission, US. Nuclear Regu latory Commisston, Wash ington, D.C. 20555. Attention:
Docketing and Service Regulatory Guides are issued to describe and make available to the public methods Branch.  acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions or postulated accidents, or to provide guidance to applicants.


Regulatory Guides are not substitutes for regulations, and compliance with them is not required.
to delineate techniques used by the Staff in Osalu The guides are issued in the following tIn broad divisions cling specific problems or postulated accidents, at to provide guidance to appli cents. Regulatory Guides ate not substitutes for regulations, and compliance i. Power Aeacti's 6 Products with them is tal required Malhods and solutions dilflatent from those sat out in 2. Research and Test Reactors 7 Transportation the guides will be acceptable if they provide a basis for the findings requisite to I. Fuels and Materials Facilities
8. Occupational Health the issuance Ot continuance ofe permit or license by the Commission
4 Environmental and Siting S. Antitrust Review Comments and suggestions fo, improvements in these guides are encouraged
5 Materials end Plant Protection
10. General at alf times, and guides will be revised, as appropriate, to accommodate cam ments and to reflect new rnfotmation or esperiance However. comments on Copies of published guides may be obtained by written request indicating the this guide. if received within about two months after its issuance, will be par divisions desited to the U S Nuclear Regulatory Commilsion.


1. Power Reactors 6. Products Methods and solutions different from those set out in the guides will be accept- 2. Research and Test Reactors 7. Transportation able if they provide a basis for the findings requisite to the issuance or continuance
Washington.
3. Fuels and Materials Facilities
8. Occupational Health of a permit or license by the Commission.


4. Environmental and Siting 9. Antitrust Review, 5. Materials and Plant Protection
D.C.ticularle useful in evaluating the need foran early revision 20%6. Attention.
10. General Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides (which may be reproduced)
or for place times, and guides will be revised, as appropriate, to accommodate comments and ment on an automatic distribution list for single copies of future guides in specific to reflect new information or experience.


This guide was revised as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission, substantive comments received from the public and additional staff review. Washington, D.C. 20555, Attention:
Director, Office o0 Standards Development.
Director, Division of Document Control.


derived from the analysis of the supporting structure.
* account for possible dynamic interaction effects. Such equipmlent can be analyzed by combining the complete equipment model with the model of the supporting structure and applying the proper excitation to the base* of the supporting structure.


This guide, addresses the acceptability and develop ment of floor design response spectra only. Time history motions that'WIill give results comparable to the floor design response spectra are also acceptable.
With this method, no sepa-*rate equipment-support excitations need be generated because the equipment will be excited directly through the structure.


There are, however, other major equipment sys tems such as the reactor coolant system whose stiff ness, mass, and resulting frequency range should be considered for inclusion in the model of the support ing structure to account for possible dynamic interac tion effects. Such equipment can be analyzed by combining the complete equipment model with the model of the supporting structure and applying the proper excitation to the base of the supporting struc ture. With this method, no separate equipment support excitations need be generated because the equipment will be excited directly through the struc ture. It should be noted that a combined model of the building and equipment must be formulated to per form such an analysis.1. Floor Response Spectra The two horizontal and the vertical response spectra can be computed from the time-history mo tions of the supporting structure at the various floors or other equipment-support locations of interest.
It should be noted that a combined model of the building and equipment must be formulated to perform such an analysis.I. Floor Response Spectra The two horizontal and the vertical response spectra* can be computed from the time-history motions of the* supporting structure at the various floors or other equip-ment-support locations of interest.


It is important that the spectrum 'ordinates be computed at the natural frequencies of the supporting structure and at frequencies sufficiently close to produce accu rate response spectra (see Table 1 for guidance).
The spectrum ordi-.nates should be computed at frequency intervals sufficiently small to produce accurate response spectra (see Table 1 for guidance).  
Spectrum peaks normally would be expected to occur at the natural frequencies of the supporting structure.
Spectrum peaks normally would be expected to occur at the natural frequencies of the supporting structure.


TABLE 1 SUGGESTED  
2. Smoothing Floor Response Spectra and Broadening Peaks To account for variations in the structural frequencies owing to -uncertainties in the material properties of the* structure and soil and to approximations in the modeling techniques used in seismic analysis, the computed floor response spectra should be smoothed, and peaks asso-ciated with each of the structural frequencies should be broadened.
 
One acceptable method for determining the amount of peak broadening associated with each of the structural frequencies is described below.Let fj be the Jth mode structural frequency that is determined from the mathematical models. The varia-tion in each of the structural frequencies is determined by evaluating the variation due to each significant para-meter such as the soil modulus, material density, etc.The total frequency variation, +/-.eAfj, (see Figure 1) is then determined by taking the square root of the sum of* squares (SRSS) of a minimum variation of 0.05fj and the individual frequency variations, A(Jn, as described in regulatory position 1.Figure 1 shows a sample of a smoothed floor response spectrum curve. Note that the broadened peak is bounded on each side by lines that are parallel to the lines forming the original spectrum peak.3. Floor Design Response Spectra* Nuclear power plant facilities are designed for three-component earthquakes, as indicated in Regulatory Guide 1.60, "De.sign Response Spectra for Seismic Design of Nuclear Power Plants." When a structural seismic analysis is performed separately for each direc-tion (two horizontal and one vertical), and in the case of TABLE 1 SUGGESTED  
FREQUENCY  
FREQUENCY  
INTERVALS  
INTERVALS  
FOR CALCULATION  
FOR CALCULATION  
OF RESPONSE SPECTRA Frequency Range Increment (hertz) (hertz) 0.2- 3.0 0.10 3.0- 3.6 0.15 3.6- 5.0 0.20 5.0- 8.0 0.25 8.0-15.0 0.50 15.0-18.0  
OF RESPONSE SPECTRA Frequency Range Increment (hertz) (hertz)0.2- 3.0 0.10 3.0- 3.6 0.15 3.6- 5.0 0.20 5.0- 8.0 0.25 8.0- 15.0 0.50 15.0- 18.0 1.0 18.0-22.0  
1.0 18.0-22.0  
2.0 22.0 -34.0 3.0 unsymmetric structures, the structural motion in a given direction at a given location will contain contributions from the vertical and the two horizontal excitations.
2.0 22.0-34.0  
3.0 2. Smoothing Floor Response Spectra and Broadening Peaks To account for uncertainties in the structural fre quencies owing to uncertainties in the material prop erties of the structure and soil and to approximations in the modeling techniques used in seismic analysis, it is important that the computed floor response spectra be smoothed and peaks associated with each of the structural frequencies be broadened.
 
One ac ceptable method for determining the amount of peak broadening associated with each of the structural fre quencies is described below.  Let fj be the Jth mode structural frequency that is determined from the mathematical models. The varia tion in each of the structural frequencies is deter mined by evaluating the variation due to each signifi cant parameter such as the soil modulus, material density, etc. The total frequency variation, +/-tAfi, (see Fig. 1) is then determined by taking the square root of the sum of squares (SRSS) of a minimum var iation of 0.05fj and the individual frequency varia tions, Afin, as described in regulatory position 1.  Figure 1 shows a sample of a smoothed floor re sponse spectrum curve. Note that the broadened peak is bounded on each side by lines that are parallel to the lines forming the original spectrum peak.  3. Floor Design Response Spectra Nuclear power plant facilities are designed for three-component earthquakes, as indicated in Regula tory Guide 1.60, "Design Response Spectra for Seismic Design of Nuclear Power Plants." When a structural seismic analysis is performed separately for each direction (two horizontal and one vertical), and in the case of unsymmetric structures, the structural motion in a given direction at a given location will contain contributions from the vertical and the two horizontal excitations.
 
In such cases, the contribution from each individual analysis will generate a re sponse spectrum at a given location in each of the three directions.


It is important that the ordinates of these three response spectra for a given direction be combined according to the SRSS criterion and that the resulting response spectrum then be smoothed and the peaks broadened to predict the floor design re sponse spectrum at the location of interest and for the given direction.
In such cases, the contribution from each Individual analysis will generate a response spectrum at a given location in each of the three directions.


In the case of symmetric structures, there will be only one significant floor response spec trum in each of the three directions.
The ordinates of these three smoothed response spectra (with peaks broadened)
for a given direction should be combined according to the SRSS criterion to predict the floor design response spectrum at the given location and for the given direction.


The smoothed versions of these floor response spectra will be the floor design response spectra. In those cases in which the mathematical model is subjected simultaneously to the action of three statistically independent spatial components*
In the case of symmetric structures, there will be only one floor response spectrum in each of the three directions.
of an earthquake, the three computed and smoothed floor response spectra at a given loca tion will be the floor design response spectra.


C. REGULATORY  
The smoothed versions of these floor response spectra will be the floor design response spectra. In those cases in which the mathematical model is subjected simultaneously to the action of three spatial components of an earthquake, the three computed and smoothed floor response spectra at a given level will be the floor design response spectra.C. REGULATORY  
POSITION The following procedures for combining and smoothing the floor response spectra (with peaks broadened)  
POSITION The following procedures for smoothing the floor response spectra (with peaks broadened)  
to obtain the smoothed floor design re sponse spectra are acceptable to the NRC staff.  *See Regulatory Guide 1.92, "Combining Modal Responses and Spatial Components in Seismic Response Analysis." 1.122-2 I I I
and combining the smoothed floor response spectra to obtain the floor design response spectra are acceptable to the NRC staff: 1. To account for variations In the structural fre-quencies owing to uncertainties in such parameters as the material properties of the structure and soil, damping values, soil-structure interaction techniques, and the approximations In the modeling techniques used in seismic analysis, the computed floor response spectra 1.122-2 z 0 L-t~J ILl VJ.2 .3 .4 .5 .6 .7.8.91. 2. 3. 4. 5. 6. 7. 8.9.10.COMPUTED FREQUENCY (CPS)20. 30. 40. 50.60.Figure 1 Response Spectrum Peak Broadening and Smoothing irn froni the floor time-history motions should be smoothed, and peaks associated with each of tihe struc-tural frequencies should be broadened (see the sample in Figure 1) by a frequency, +Afj, where XP (Afn) ]Afj .[)=(0.05J)2  
.2 .3 .4 .5 .6 .7.8.91. 2. 3. 4. 5. 6. 7. 8.9.10. COMPUTED FREQUENCY (CPS) Figure 1 Response Spectrum Peak Broadening and Smoothing 20. 30. 40. 50.60..8.7 .6.5 .4.3 z 0 I-j L.  <C..2 .1
+ X Wild 2 1 4o0.ofJ n=l where /fJn denotes the variation in Jth mode fre.quency, f., due to variation in parameter number n, and P is the number of significant parameters considered.
1. When the seismic analysis is performed sepa rately for each of the three directions, and in the case of unsymmetric structures, the ordinates of the floor design response spectrum at the location of interest and for a given direction should be obtained by com bining the ordinates of the three floor response spectra for that direction according to the SRSS criterion.


The resulting response spectrum should be smoothed with peaks broadened.
A value of 0.10fj should be used if the actual computed value of Afj is less than 0.10fj. If the above procedure is not used, AfJ should be taken as 0.1 5fJ.2. When the seismic analysis is performed separately for each 6f the three directions, and in the case of un-symmetric structures, the ordinates of the floor Oesign response spectrum for a given direction should be obtained by combining the ordinates of the three smoothed floor response spectra for that direction according to the SRSS criterion.


In the case of sym metric structures, the floor design response spectrum for a given direction will be the smoothed floor re sponse spectrum for that direction.
In the case of symme-tric structures, the floor design response spectrum for a UNITED STATES NUCLEAR REGULATORY
COMMISSION
WASHINGTON, 0. C, 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. S300 given direction will be the smoothed floor responsefor that direction.


2. To account for uncertainties in the structural frequencies owing to uncertainties in such parameters as the material properties of the structure and soil, damping values, soil-structure interaction techniques, and the approximations in the modeling techniques used in seismic analysis, the computed floor response spectra from the floor time-history motions should be smoothed, and peaks associated with each of the structural frequencies should be broadened (see the sample in Figure 1) by a frequency, __Afi, where Afj = (0.05fj)2 n Y (Afjn)2 4 0.If, n=l where Afjn denotes the variation in the Jth mode fre quency, fj, due to variation in parameter number n, and P is the number of significant parameters consid ered. A value of 0.1fj should be used if the actual computed value of Afj is less than O.1fj. If the above procedure is not used, Afj should be taken as 0. 15fj.  3. When the mathematical model of the supporting structure is subjected simultaneously to the action of three spatial components of an earthquake, the com puted response spectrum in a given direction with peaks broadened and smoothed will be the floor de sign response spectrum in that direction.
3. When the mathematical model of the supporting structure is subjected simultaneously to the action of three spatial components of an earthquake, the computed and smoothed response spectrum in a given direction will be the floor design response spectrum in that directiotn.


==D. IMPLEMENTATION==
==D. IMPLEMENTATION==
The purpose of this section is to provide informa tion to applicants regarding the NRC staff's plans for using this regulatory guide. This guide reflects current NRC staff practice.
The purpose of this section is to piovide information to applicants regarding the NRC staff's plans for using this regulatory guide.This guide reflects current NRC staff practice.


Therefore, except in those cases in which the appli cant proposes an acceptable alternative method for complying with specified portions of the Commis sion's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for construction permit applications until this guide is revised as a result of suggestions from the public or additional staff review.1.122-4}}
There.fore, except in those cases in which tie applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for construction permit applications until this guide is revised as a result of suggestions from the public or addi-tional staff review.POSTAGE AND FEES PAID U.S. NUCLEAR REGULATORY
.r COMMISSION
-1.122-4}}


{{RG-Nav}}
{{RG-Nav}}

Revision as of 19:53, 12 October 2018

Development of Floor Design Response Spectra for Seismic Design of Floor-Supported Equipment or Components
ML13350A275
Person / Time
Issue date: 09/30/1976
From:
NRC/OSD
To:
References
RG-1.122
Download: ML13350A275 (4)
v • d • e


U.S. NUCLEAR REGULATORY

COMMISSION

REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 1.122 DEVELOPMENT

OF FLOOR DESIGN RESPONSE SPECTRA FOR SEISMIC DESIGN OF FLOOR-SUPPORTED

EQUIPMENT

OR COMPONENTS

September

1976

A. INTRODUCTION

Criterion

2, "Design Bases for Protection Against Natural Phenomena," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50,"Licensing of Production and Utilization Facilities," re-quires, in part, that nuclear power plant structures, systems, and components important to safety be de-signed to withstand the effects of earthquakes without loss of capability to perform their safety functions.

Para-graph (a)(1) of Section VI, "Application to Engineering Design," of Appendix A, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," to 10 CFR Part 100,"Reactor Site Criteria," requires, in part, that safety-related structures, systems, and components remain functional in the event of a Safe Shutdown Earthquake (SSE). It specifies the use of a suitable dynamic analysis as one method of ensuring that the structures, systems, and components can withstand the seismic loads.Similarly, paragraph (a)(2) of Section VI of the sarkl appendix requires, in part, that the structures, sy.i.ms, and components necessary for continued opezation""th- out undue risk to the health and ie remain functional in the event of an t~qratinrnBasis Earthquake (OBE). Again, the use of suit .d> .amic analysis is specified as one method of ensurt'iAiat the structures, systems, and nents can withstand the seismic loads.* This guide cri e ds acceptable to the NRC* staff for 4 l g tw ori ontal and one vertical floor design .o t various floors or other equip-ment-su locafs of interest from the time-history motions Iting from the dynamic analysis of the supporting cture. These floor design response spectra are needed for the dynamic analysis of the systems or equipment supported at various locations of the sup-porting structure.

B. DISCUSSION

Nuclear facility structures can be approximated by mathematical models to permit analysis of responses to earthquake motions. Because of the large number of degrees of freedom that would be necessaiy.

and the possible ill-conditioning of the resulting stfqiiess matrix if the complete plant were treated in a cal model, the plant is usually dvided intQ. several separate systems for analysis P.-Urs's-Thus itis usual that there arc one or more matheail models of sup-.,t" I, .= M;porting structures.

Each supporting structure normally supports one or rte systems or of equipment.

Also, different m"-.l structure may be required For these reasons, the mathen .Mo A used to generate the seismic excita-tion ..for s ects ent separate analyses of supported.syterZ,_.., -. eq~upment may not be suitable for the*t.Wed-Aoidized analyses of the supporting structure.

I'1ost equipment having a sr'all mass relative to that:of the supporting structure will 'lave negligible interac-tion effects on the support structu, -and will need to be included only in the mass distributicin of the mathemati- cal model for that structure.

For such equipment, a separate analysis will be performed using the floor design response spectra or time-history excitations at the equip-ment-support locations derived from the analysis of the supporting structure.

This guide addresses the acceptabil- ity and development of floor design response spectra only. Time-history motions that will give results comparable to the floor design response spectra are also acceptable.

There are, however, other major equipment systems such as the reactor coolant system whose stiffness, mass, and resulting frequency range should be considered for inclusion in the model of the supporting structure to USNRC REGULATORY

GUIDES Comments should be sent to the Secretary of the Commission.

U.S Nuclear Regulatory Commission.

Washington.

D.C. 2V566. Attention Docketing and Regulatory Guides ate issued to deoctibS and make available to the public Service Section.methods acceptable to the NRC sltal of implemenling specific parts of the Commission aeIgulations.

to delineate techniques used by the Staff in Osalu The guides are issued in the following tIn broad divisions cling specific problems or postulated accidents, at to provide guidance to appli cents. Regulatory Guides ate not substitutes for regulations, and compliance i. Power Aeacti's 6 Products with them is tal required Malhods and solutions dilflatent from those sat out in 2. Research and Test Reactors 7 Transportation the guides will be acceptable if they provide a basis for the findings requisite to I. Fuels and Materials Facilities

8. Occupational Health the issuance Ot continuance ofe permit or license by the Commission

4 Environmental and Siting S. Antitrust Review Comments and suggestions fo, improvements in these guides are encouraged

5 Materials end Plant Protection

10. General at alf times, and guides will be revised, as appropriate, to accommodate cam ments and to reflect new rnfotmation or esperiance However. comments on Copies of published guides may be obtained by written request indicating the this guide. if received within about two months after its issuance, will be par divisions desited to the U S Nuclear Regulatory Commilsion.

Washington.

D.C.ticularle useful in evaluating the need foran early revision 20%6. Attention.

Director, Office o0 Standards Development.

  • account for possible dynamic interaction effects. Such equipmlent can be analyzed by combining the complete equipment model with the model of the supporting structure and applying the proper excitation to the base* of the supporting structure.

With this method, no sepa-*rate equipment-support excitations need be generated because the equipment will be excited directly through the structure.

It should be noted that a combined model of the building and equipment must be formulated to perform such an analysis.I. Floor Response Spectra The two horizontal and the vertical response spectra* can be computed from the time-history motions of the* supporting structure at the various floors or other equip-ment-support locations of interest.

The spectrum ordi-.nates should be computed at frequency intervals sufficiently small to produce accurate response spectra (see Table 1 for guidance).

Spectrum peaks normally would be expected to occur at the natural frequencies of the supporting structure.

2. Smoothing Floor Response Spectra and Broadening Peaks To account for variations in the structural frequencies owing to -uncertainties in the material properties of the* structure and soil and to approximations in the modeling techniques used in seismic analysis, the computed floor response spectra should be smoothed, and peaks asso-ciated with each of the structural frequencies should be broadened.

One acceptable method for determining the amount of peak broadening associated with each of the structural frequencies is described below.Let fj be the Jth mode structural frequency that is determined from the mathematical models. The varia-tion in each of the structural frequencies is determined by evaluating the variation due to each significant para-meter such as the soil modulus, material density, etc.The total frequency variation, +/-.eAfj, (see Figure 1) is then determined by taking the square root of the sum of* squares (SRSS) of a minimum variation of 0.05fj and the individual frequency variations, A(Jn, as described in regulatory position 1.Figure 1 shows a sample of a smoothed floor response spectrum curve. Note that the broadened peak is bounded on each side by lines that are parallel to the lines forming the original spectrum peak.3. Floor Design Response Spectra* Nuclear power plant facilities are designed for three-component earthquakes, as indicated in Regulatory Guide 1.60, "De.sign Response Spectra for Seismic Design of Nuclear Power Plants." When a structural seismic analysis is performed separately for each direc-tion (two horizontal and one vertical), and in the case of TABLE 1 SUGGESTED

FREQUENCY

INTERVALS

FOR CALCULATION

OF RESPONSE SPECTRA Frequency Range Increment (hertz) (hertz)0.2- 3.0 0.10 3.0- 3.6 0.15 3.6- 5.0 0.20 5.0- 8.0 0.25 8.0- 15.0 0.50 15.0- 18.0 1.0 18.0-22.0

2.0 22.0 -34.0 3.0 unsymmetric structures, the structural motion in a given direction at a given location will contain contributions from the vertical and the two horizontal excitations.

In such cases, the contribution from each Individual analysis will generate a response spectrum at a given location in each of the three directions.

The ordinates of these three smoothed response spectra (with peaks broadened)

for a given direction should be combined according to the SRSS criterion to predict the floor design response spectrum at the given location and for the given direction.

In the case of symmetric structures, there will be only one floor response spectrum in each of the three directions.

The smoothed versions of these floor response spectra will be the floor design response spectra. In those cases in which the mathematical model is subjected simultaneously to the action of three spatial components of an earthquake, the three computed and smoothed floor response spectra at a given level will be the floor design response spectra.C. REGULATORY

POSITION The following procedures for smoothing the floor response spectra (with peaks broadened)

and combining the smoothed floor response spectra to obtain the floor design response spectra are acceptable to the NRC staff: 1. To account for variations In the structural fre-quencies owing to uncertainties in such parameters as the material properties of the structure and soil, damping values, soil-structure interaction techniques, and the approximations In the modeling techniques used in seismic analysis, the computed floor response spectra 1.122-2 z 0 L-t~J ILl VJ.2 .3 .4 .5 .6 .7.8.91. 2. 3. 4. 5. 6. 7. 8.9.10.COMPUTED FREQUENCY (CPS)20. 30. 40. 50.60.Figure 1 Response Spectrum Peak Broadening and Smoothing irn froni the floor time-history motions should be smoothed, and peaks associated with each of tihe struc-tural frequencies should be broadened (see the sample in Figure 1) by a frequency, +Afj, where XP (Afn) ]Afj .[)=(0.05J)2

+ X Wild 2 1 4o0.ofJ n=l where /fJn denotes the variation in Jth mode fre.quency, f., due to variation in parameter number n, and P is the number of significant parameters considered.

A value of 0.10fj should be used if the actual computed value of Afj is less than 0.10fj. If the above procedure is not used, AfJ should be taken as 0.1 5fJ.2. When the seismic analysis is performed separately for each 6f the three directions, and in the case of un-symmetric structures, the ordinates of the floor Oesign response spectrum for a given direction should be obtained by combining the ordinates of the three smoothed floor response spectra for that direction according to the SRSS criterion.

In the case of symme-tric structures, the floor design response spectrum for a UNITED STATES NUCLEAR REGULATORY

COMMISSION

WASHINGTON, 0. C, 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. S300 given direction will be the smoothed floor responsefor that direction.

3. When the mathematical model of the supporting structure is subjected simultaneously to the action of three spatial components of an earthquake, the computed and smoothed response spectrum in a given direction will be the floor design response spectrum in that directiotn.

D. IMPLEMENTATION

The purpose of this section is to piovide information to applicants regarding the NRC staff's plans for using this regulatory guide.This guide reflects current NRC staff practice.

There.fore, except in those cases in which tie applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for construction permit applications until this guide is revised as a result of suggestions from the public or addi-tional staff review.POSTAGE AND FEES PAID U.S. NUCLEAR REGULATORY

.r COMMISSION

-1.122-4


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