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{{Adams
{{Adams
| number = ML13350A275
| number = ML003739367
| issue date = 09/30/1976
| issue date = 02/28/1978
| 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/OSD
| author affiliation = NRC/RES
| addressee name =  
| addressee name =  
| addressee affiliation =  
| addressee affiliation =  
Line 10: Line 10:
| license number =  
| license number =  
| contact person =  
| contact person =  
| document report number = RG-1.122
| document report number = RG-1.122, Rev 1
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 4
| page count = 4
}}
}}
{{#Wiki_filter:U.S. NUCLEAR REGULATORY  
{{#Wiki_filter:Revision 1 U.S. NUCLEAR REGULATORY COMMISSION                                                                                 February 1978 REGULATORY GUIDE
COMMISSION
                                      OFFICE OF STANDARDS DEVELOPMENT
REGULATORY  
                                                                      REGULATORY GUIDE 1.122 DEVELOPMENT OF FLOOR DESIGN RESPONSE SPECTRA
GUIDE OFFICE OF STANDARDS  
                                  FOR SEISMIC DESIGN OF FLOOR-SUPPORTED EQUIPMENT OR
DEVELOPMENT
                                                                                  COMPONENTS
REGULATORY  
GUIDE 1.122 DEVELOPMENT  
OF FLOOR DESIGN RESPONSE SPECTRA FOR SEISMIC DESIGN OF FLOOR-SUPPORTED  
EQUIPMENT  
OR COMPONENTS
September
1976


==A. INTRODUCTION==
==A. INTRODUCTION==
Criterion  
analysis of the systems or equipment supported at Criterion 2, "Design Bases for Protection Against                                       various locations of the supporting structure. The Natural Phenomena," of Appendix A, "General De                                              Advisory Committee on Reactor Safeguards has been sign Criteria for Nuclear Power Plants," to 10 CFR                                         -consulted concerning this guide and has concurred in Part 50, "Licensing of Production and Utilization                                           ýthe regulatory position.
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.
Facilities," requires, in part, that nuclear power-plant structures, systems, and components important to                                                                        


==B. DISCUSSION==
==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.
safety be designed to withstand the effects of earth                                            Nuclear facility structures can be approximated by quakes without loss of capability to perform their                                          mathematical models to permit analysis of responses safety functions. Paragraph (a)(1) of Section VI,                                            to earthquake motions. Because of the large number
  "Application to Engineering Design," of Appendix                                            of degrees of freedom that would be necessary and A, "Seismic and Geologic Siting Criteria for Nuclear                                          the possible ill-conditioning of the resulting stiffness Power Plants," to 10 CFR Part 100, "Reactor Site                                            matrix if the complete plant were treated in a single Criteria," requires, in part, that safety-related struc                                      mathematical model, the plant is usually divided into tures, systems, and components remain functional in                                          several separate systems for analysis purposes. Thus the event of a Safe Shutdown Earthquake (SSE). It                                            it is usual that there are one or more mathematical specifies the use of a suitable dynamic analysis as                                          models of supporting structures. Each supporting one method of ensuring that the structures, systems,                                        structure normally supports one or more systems or and components can withstand the seismic loads.                                              pieces of equipment. Also, different models of the Similarly, paragraph (a)(2) of Section VI of the same                                        same structure may be required for different pur appendix requires, in part, that the structures, sys                                        poses. For these reasons, the mathematical models tems, and components necessary for continued opera                                          used to generate the seismic excitation data for sub tion without undue risk to the health and safety of the                                      sequent separate analyses of supported systems or public remain functional in the event of an Operating                                        equipment may not be suitable for the detailed lo Basis Earthquake (OBE). Again, the use of suitable                                          calized analyses 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.
dynamic analysis is specified as one method of ensur ing that the structures, systems, and components can                                            Most equipment having a small mass relative to withstand the seismic loads.                                                                that of the supporting structure will have negligible interaction effects on the support structure and will This guide describes methods acceptable to the                                         need to be included only in the mass distribution of NRC staff for developing two horizontal and one ver                                          the mathematical model for that structure. For such tical floor design response spectra at various floors or                                    equipment, a separate analysis will be performed other equipment-support locations of interest from                                          using the floor design response spectra or time the time-history motions resulting from the dynamic                                          history excitations at the equipment-support locations analysis of the supporting structure. These floor de sign response spectra are needed for the dynamic
                                                                                            *Lines indicate substantive changes from previous issue.


Each supporting structure normally supports one or rte systems or of equipment.
USNRC REGULATORY GUIDES                                              Comments should be sent to the Secretary of the Commission, US. Nuclear Regu Regulatory Guides are issued to describe and make available to the public                latory Commisston, Wash ington, D.C. 20555. Attention: Docketing and Service methods    Branch.


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.
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 are not substitutes for regulations, and compliance with them is                Guides not required.    1. Power Reactors                          6.


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


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.
4.


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.
5.  Environmental  and Siting Materials and Plant                    9.  Antitrust Review, Protection
                                                                                                                                      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)
times, and guides will be revised, as appropriate, to accommodate comments                                                                                        or for place and  ment on an automatic distribution list for single copies of future guides to reflect new information or experience. This guide was revised as                                                                                                  in specific a result of  divisions should be made in writing to the US. Nuclear Regulatory substantive comments received from the public and additional staff                                                                                                Commission, review.  Washington, D.C.      20555, Attention: Director, Division of Document Control.


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
derived from the analysis of the supporting structure.      of the structural frequencies be broadened. One ac This guide, addresses the acceptability and develop          ceptable method for determining the amount of peak ment of floor design response spectra only. Time            broadening associated with each of the structural fre history motions that'WIill give results comparable to        quencies is described below.
GUIDES Comments should be sent to the Secretary of the Commission.


U.S Nuclear Regulatory Commission.
the floor design response spectra are also acceptable.           Let fj be the Jth mode structural frequency that is There are, however, other major equipment sys            determined from the mathematical models. The varia tems such as the reactor coolant system whose stiff          tion in each of the structural frequencies is deter ness, mass, and resulting frequency range should be          mined by evaluating the variation due to each signifi considered for inclusion in the model of the support        cant parameter such as the soil modulus, material ing structure to account for possible dynamic interac        density, etc. The total frequency variation, +/-tAfi, tion effects. Such equipment can be analyzed by              (see Fig. 1) is then determined by taking the square combining the complete equipment model with the              root of the sum of squares (SRSS) of a minimum var model of the supporting structure and applying the          iation of 0.05fj and the individual frequency varia proper excitation to the base of the supporting struc        tions, Afin, as described in regulatory position 1.


Washington.
ture. With this method, no separate equipment                    Figure 1 shows a sample of a smoothed floor re support excitations need be generated because the sponse spectrum curve. Note that the broadened peak equipment will be excited directly through the struc        is bounded on each side by lines that are parallel to ture. It should be noted that a combined model of the        the lines forming the original spectrum peak.


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.
building and equipment must be formulated to per form such an analysis.                                        3. Floor Design Response Spectra
  1. Floor Response Spectra                                      Nuclear power plant facilities are designed for three-component earthquakes, as indicated in Regula The two horizontal and the vertical response tory Guide 1.60, "Design Response Spectra for spectra can be computed from the time-history mo Seismic Design of Nuclear Power Plants." When a tions of the supporting structure at the various floors      structural seismic analysis is performed separately for or other equipment-support locations of interest. It is each direction (two horizontal and one vertical), and important that the spectrum 'ordinates be computed at in the case of unsymmetric structures, the structural the natural frequencies of the supporting structure I and at frequencies sufficiently close to produce accu rate response spectra (see Table 1 for guidance).
                                                              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 Spectrum peaks normally would be expected to occur from each individual analysis will generate a re at the natural frequencies of the supporting structure.


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
sponse spectrum at a given location in each of the TABLE 1                              three directions. It is important that the ordinates of these three response spectra for a given direction be SUGGESTED FREQUENCY INTERVALS FOR                        combined according to the SRSS criterion and that CALCULATION OF RESPONSE SPECTRA                        the resulting response spectrum then be smoothed and the peaks broadened to predict the floor design re Frequency                                        sponse spectrum at the location of interest and for the Range                    Increment          given direction. In the case of symmetric structures, (hertz)                    (hertz)
8. Occupational Health the issuance Ot continuance ofe permit or license by the Commission
                                                              there will be only one significant floor response spec trum in each of the three direction
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.
====s. The smoothed====
              0.2- 3.0                      0.10
                                                              versions of these floor response spectra will be the
              3.0- 3.6                      0.15 floor design response spectra. In those cases in which
              3.6- 5.0                      0.20
                                                              the mathematical model is subjected simultaneously
              5.0- 8.0                      0.25 to the action of three statistically independent spatial
              8.0-15.0                      0.50
                                                              components* of an earthquake, the three computed
              15.0-18.0                      1.0
                                                                and smoothed floor response spectra at a given loca
              18.0-22.0                      2.0              tion will be the floor design response spectra.


D.C.ticularle useful in evaluating the need foran early revision 20%6. Attention.
22.0-34.0                      3.0


Director, Office o0 Standards Development.
==C. REGULATORY POSITION==
2. Smoothing Floor Response Spectra and                        The following procedures for combining and Broadening Peaks smoothing the floor response spectra (with peaks To account for uncertainties in the structural fre        broadened) to obtain the smoothed floor design re quencies owing to uncertainties in the material prop        sponse spectra are acceptable to the NRC staff.


* 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.
erties of the structure and soil and to approximations in the modeling techniques used in seismic analysis,
                                                                *See Regulatory Guide 1.92, "Combining Modal Responses and it is important that the computed floor response Spatial Components in Seismic Response Analysis."
  spectra be smoothed and peaks associated with each
                                                          1.122-2 I I


With this method, no sepa-*rate equipment-support excitations need be generated because the equipment will be excited directly through the structure.
.8
    .7
    .6
    .5 z
0
I
    .4
<C.


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.
-j L.


The spectrum ordi-.nates should be computed at frequency intervals sufficiently small to produce accurate response spectra (see Table 1 for guidance).  
.3
Spectrum peaks normally would be expected to occur at the natural frequencies of the supporting structure.
    .2
    .1
      .2 .3  .4  .5 .6 .7.8.91.        2.    3. 4. 5. 6. 7. 8.9.10. 20. 30. 40. 50.60.


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.
COMPUTED FREQUENCY (CPS)
            Figure 1 Response Spectrum Peak Broadening and Smoothing


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
1. When the seismic analysis is performed sepa          where Afjn denotes the variation in the Jth mode fre rately for each of the three directions, and in the case    quency, fj, due to variation in parameter number n, of unsymmetric structures, the ordinates of the floor      and P is the number of significant parameters consid design response spectrum at the location of interest        ered. A value of 0.1fj should be used if the actual and for a given direction should be obtained by com        computed value of Afj is less than O.1fj. If the above bining the ordinates of the three floor response            procedure is not used, Afj should be taken as 0. 15fj.
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.
spectra for that direction according to the SRSS              3. When the mathematical model of the supporting criterion. The resulting response spectrum should be        structure is subjected simultaneously to the action of smoothed with peaks broadened. In the case of sym          three spatial components of an earthquake, the com metric structures, the floor design response spectrum      puted response spectrum in a given direction with for a given direction will be the smoothed floor re        peaks broadened and smoothed will be the floor de sponse spectrum for that direction.                        sign response spectrum in that direction.


The ordinates of these three smoothed response spectra (with peaks broadened)
2. To account for uncertainties in the structural                     
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.
==D. IMPLEMENTATION==
frequencies owing to uncertainties in such parameters as the material properties of the structure and soil,          The purpose of this section is to provide informa damping values, soil-structure interaction techniques,     tion to applicants regarding the NRC staff's plans for and the approximations in the modeling techniques          using this regulatory guide.


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
used in seismic analysis, the computed floor response         This guide reflects current NRC staff practice.
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.
spectra from the floor time-history motions should be       Therefore, except in those cases in which the appli smoothed, and peaks associated with each of the             cant proposes an acceptable alternative method for structural frequencies should be broadened (see the         complying with specified portions of the Commis sample in Figure 1) by a frequency, __Afi, where            sion's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for construction permit applications Afj  =      (0.05fj) 2  nY    (Afjn)2      4  0.If, until this guide is revised as a result of suggestions n=l from the public or additional staff review.
 
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
1.122-4}}
.r COMMISSION
-1.122-4}}


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Latest revision as of 11:40, 28 March 2020

Development of Floor Design Response Spectra for Seismic Design of Floor-Supported Equipment or Components
ML003739367
Person / Time
Issue date: 02/28/1978
From:
Office of Nuclear Regulatory Research
To:
References
RG-1.122, Rev 1
Download: ML003739367 (4)
v • d • e


Revision 1 U.S. NUCLEAR REGULATORY COMMISSION February 1978 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

A. INTRODUCTION

analysis of the systems or equipment supported at Criterion 2, "Design Bases for Protection Against various locations of the supporting structure. The Natural Phenomena," of Appendix A, "General De Advisory Committee on Reactor Safeguards has been sign Criteria for Nuclear Power Plants," to 10 CFR -consulted concerning this guide and has concurred in Part 50, "Licensing of Production and Utilization ýthe regulatory position.

Facilities," requires, in part, that nuclear power-plant structures, systems, and components important to

B. DISCUSSION

safety be designed to withstand the effects of earth Nuclear facility structures can be approximated by quakes without loss of capability to perform their mathematical models to permit analysis of responses safety functions. Paragraph (a)(1) of Section VI, to earthquake motions. Because of the large number

"Application to Engineering Design," of Appendix of degrees of freedom that would be necessary and A, "Seismic and Geologic Siting Criteria for Nuclear the possible ill-conditioning of the resulting stiffness Power Plants," to 10 CFR Part 100, "Reactor Site matrix if the complete plant were treated in a single Criteria," requires, in part, that safety-related struc mathematical model, the plant is usually divided into tures, systems, and components remain functional in several separate systems for analysis purposes. Thus the event of a Safe Shutdown Earthquake (SSE). It it is usual that there are one or more mathematical specifies the use of a suitable dynamic analysis as models of supporting structures. Each supporting one method of ensuring that the structures, systems, structure normally supports one or more systems or and components can withstand the seismic loads. pieces of equipment. Also, different models of the Similarly, paragraph (a)(2) of Section VI of the same same structure may be required for different pur appendix requires, in part, that the structures, sys poses. For these reasons, the mathematical models tems, and components necessary for continued opera used to generate the seismic excitation data for sub tion without undue risk to the health and safety of the sequent separate analyses of supported systems or public remain functional in the event of an Operating equipment may not be suitable for the detailed lo Basis Earthquake (OBE). Again, the use of suitable calized analyses of the supporting structure.

dynamic analysis is specified as one method of ensur ing that the structures, systems, and components can Most equipment having a small mass relative to withstand the seismic loads. that of the supporting structure will have negligible interaction effects on the support structure and will This guide describes methods acceptable to the need to be included only in the mass distribution of NRC staff for developing two horizontal and one ver the mathematical model for that structure. For such tical floor design response spectra at various floors or equipment, a separate analysis will be performed other equipment-support locations of interest from using the floor design response spectra or time the time-history motions resulting from the dynamic history excitations at the equipment-support locations analysis of the supporting structure. These floor de sign response spectra are needed for the dynamic

  • Lines indicate substantive changes from previous issue.

USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commission, US. Nuclear Regu Regulatory Guides are issued to describe and make available to the public latory Commisston, Wash ington, D.C. 20555. Attention: Docketing and Service 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 are not substitutes for regulations, and compliance with them is Guides not required. 1. Power Reactors 6.

Methods and solutions different from those set out in the guides will Products be accept- 2. Research and Test Reactors 7. Transportation able if they provide a basis for the findings requisite to the issuance or continuance

3. Fuels and Materials Facilities 8. Occupational Health of a permit or license by the Commission.

4.

5. Environmental and Siting Materials and Plant 9. Antitrust Review, Protection

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)

times, and guides will be revised, as appropriate, to accommodate comments or for place and ment on an automatic distribution list for single copies of future guides to reflect new information or experience. This guide was revised as in specific a result of divisions should be made in writing to the US. Nuclear Regulatory substantive comments received from the public and additional staff Commission, review. Washington, D.C. 20555, Attention: Director, Division of Document Control.

derived from the analysis of the supporting structure. of the structural frequencies be broadened. One ac This guide, addresses the acceptability and develop ceptable method for determining the amount of peak ment of floor design response spectra only. Time broadening associated with each of the structural fre history motions that'WIill give results comparable to quencies is described below.

the floor design response spectra are also acceptable. Let fj be the Jth mode structural frequency that is There are, however, other major equipment sys determined from the mathematical models. The varia tems such as the reactor coolant system whose stiff tion in each of the structural frequencies is deter ness, mass, and resulting frequency range should be mined by evaluating the variation due to each signifi considered for inclusion in the model of the support cant parameter such as the soil modulus, material ing structure to account for possible dynamic interac density, etc. The total frequency variation, +/-tAfi, tion effects. Such equipment can be analyzed by (see Fig. 1) is then determined by taking the square combining the complete equipment model with the root of the sum of squares (SRSS) of a minimum var model of the supporting structure and applying the iation of 0.05fj and the individual frequency varia proper excitation to the base of the supporting struc tions, Afin, as described in regulatory position 1.

ture. With this method, no separate equipment Figure 1 shows a sample of a smoothed floor re support excitations need be generated because the sponse spectrum curve. Note that the broadened peak equipment will be excited directly through the struc is bounded on each side by lines that are parallel to ture. It should be noted that a combined model of the the lines forming the original spectrum peak.

building and equipment must be formulated to per form such an analysis. 3. Floor Design Response Spectra

1. Floor Response Spectra Nuclear power plant facilities are designed for three-component earthquakes, as indicated in Regula The two horizontal and the vertical response tory Guide 1.60, "Design Response Spectra for spectra can be computed from the time-history mo Seismic Design of Nuclear Power Plants." When a tions of the supporting structure at the various floors structural seismic analysis is performed separately for or other equipment-support locations of interest. It is each direction (two horizontal and one vertical), and important that the spectrum 'ordinates be computed at in the case of unsymmetric structures, the structural the natural frequencies of the supporting structure I and at frequencies sufficiently close to produce accu rate response spectra (see Table 1 for guidance).

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 Spectrum peaks normally would be expected to occur from each individual analysis will generate a re at the natural frequencies of the supporting structure.

sponse spectrum at a given location in each of the TABLE 1 three directions. It is important that the ordinates of these three response spectra for a given direction be SUGGESTED FREQUENCY INTERVALS FOR combined according to the SRSS criterion and that CALCULATION OF RESPONSE SPECTRA the resulting response spectrum then be smoothed and the peaks broadened to predict the floor design re Frequency sponse spectrum at the location of interest and for the Range Increment given direction. In the case of symmetric structures, (hertz) (hertz)

there will be only one significant floor response spec trum in each of the three direction

s. The smoothed

0.2- 3.0 0.10

versions of these floor response spectra will be the

3.0- 3.6 0.15 floor design response spectra. In those cases in which

3.6- 5.0 0.20

the mathematical model is subjected simultaneously

5.0- 8.0 0.25 to the action of three statistically independent spatial

8.0-15.0 0.50

components* of an earthquake, the three computed

15.0-18.0 1.0

and smoothed floor response spectra at a given loca

18.0-22.0 2.0 tion will be the floor design response spectra.

22.0-34.0 3.0

C. REGULATORY POSITION

2. Smoothing Floor Response Spectra and The following procedures for combining and Broadening Peaks smoothing the floor response spectra (with peaks To account for uncertainties in the structural fre broadened) to obtain the smoothed floor design re quencies owing to uncertainties in the material prop sponse spectra are acceptable to the NRC staff.

erties of the structure and soil and to approximations in the modeling techniques used in seismic analysis,

  • See Regulatory Guide 1.92, "Combining Modal Responses and it is important that the computed floor response Spatial Components in Seismic Response Analysis."

spectra be smoothed and peaks associated with each

1.122-2 I I

.8

.7

.6

.5 z

0

I

.4

<C.

-j L.

.3

.2

.1

.2 .3 .4 .5 .6 .7.8.91. 2. 3. 4. 5. 6. 7. 8.9.10. 20. 30. 40. 50.60.

COMPUTED FREQUENCY (CPS)

Figure 1 Response Spectrum Peak Broadening and Smoothing

1. When the seismic analysis is performed sepa where Afjn denotes the variation in the Jth mode fre rately for each of the three directions, and in the case quency, fj, due to variation in parameter number n, of unsymmetric structures, the ordinates of the floor and P is the number of significant parameters consid design response spectrum at the location of interest ered. A value of 0.1fj should be used if the actual and for a given direction should be obtained by com computed value of Afj is less than O.1fj. If the above bining the ordinates of the three floor response procedure is not used, Afj should be taken as 0. 15fj.

spectra for that direction according to the SRSS 3. When the mathematical model of the supporting criterion. The resulting response spectrum should be structure is subjected simultaneously to the action of smoothed with peaks broadened. In the case of sym three spatial components of an earthquake, the com metric structures, the floor design response spectrum puted response spectrum in a given direction with for a given direction will be the smoothed floor re peaks broadened and smoothed will be the floor de sponse spectrum for that direction. sign response spectrum in that direction.

2. To account for uncertainties in the structural

D. IMPLEMENTATION

frequencies owing to uncertainties in such parameters as the material properties of the structure and soil, The purpose of this section is to provide informa damping values, soil-structure interaction techniques, tion to applicants regarding the NRC staff's plans for and the approximations in the modeling techniques using this regulatory guide.

used in seismic analysis, the computed floor response This guide reflects current NRC staff practice.

spectra from the floor time-history motions should be Therefore, except in those cases in which the appli smoothed, and peaks associated with each of the cant proposes an acceptable alternative method for structural frequencies should be broadened (see the complying with specified portions of the Commis sample in Figure 1) by a frequency, __Afi, where sion's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for construction permit applications Afj = (0.05fj) 2 nY (Afjn)2 4 0.If, until this guide is revised as a result of suggestions n=l from the public or additional staff review.

1.122-4


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