Regulatory Guide 1.60

Design Response Spectra for Seismic Design of Nuclear Power Plants

ML003740207
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Issue date:	12/31/1973
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RG-1.60, Rev 1
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Revssion I

December 1973 U.S. ATOMIC ENERGY COMMISSION

REGULATORY

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 1.60

DESIGN RESPONSE SPECTRA FOR SEISMIC DESIGN

OF NUCLEAR POWER PLANTS

A. INTRODUCTION

Criterion 2, "Design Bases for Protection Against Natural Phenomena t' of Appendix A. "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50.

"Uicensing 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 earthquakes.

Proptsed Appendix A, "Seismic and Geologic Siting Criteria." to 10 CFR Part 100, "Reactor Site Criteria,"

would require, in part, that the Safe Shutdown Eartlhquake (SSE) be defined by response spectra co, responding to the expected maximum ground aiccelcrations.

This guide describes a

procedure acceptable to the AEC Regulatory staff for defining response spectra for the seismic design of nuclear power plants. The Adviory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.

B. DISCUSSION

In order to approximate the intensity and thereby estimate the maximum ground acceleration' of the expected strongest ground motion (SSE) for a given site, proposed Appendix A to 10 CFR Part 100 specifies a number of required investigations. It does not. however, give a method for defining 1he response spectral coriesponding to the expected maximum ground acceleralion.

Tit recorded ground accelerations and response spectlra of past earthquakes prwvide a basis for the ralional designi of structures to resist earthquakes. The Design Response Spectra.' specified for design purposes, can he developed statistically fromn response spectra of past strong-notion earthquakes (see reference I). An I Sce deftintions at the end of the guide.

extensive study has been described by Newmark and filurne in references 1, 2, and 3. After reviewing these referenced documents, the AEC Regulatory staff has determined as acceptable the following procedure for defining the Design Response Spectta representing the effects of the vibratory motion of the SSE, 1/2 the SSE,

and the Operating Basis Earthquake (OBE) on sites underlain by either rock or soil deposits and covering all frequencies of interest. However, for unusually soft sites, modification to this procedure will be required.

In this procedure, the configurations of the horizontal component Design Response Spectra for each of the two mutually perpendicular horizontal axes are shown in Figure I of this guide. These shapes agree with those developed by Newmark, Blum

e. and Kapur in

,eference 1. In Figure I the base diagram consists of three parts: the bottom line on the left part represents the maximum ground displacement, the bottom line on the right part represents the maximum acceleration, and the middle part depends on the maximum velocity. The horizontal component Design Response Spectra in Figure I of this guide correspond to a maximum horizontal rou'nd accehiration of 1.0 g. The maximum ground displacement is taken proportional to the maximum ground acceleration, and is set at 36 inches for a ground acceleration of 1.0 g. The numerical values of design displacements, velocities, and accelerations for the horizontal component Design Response Spectra are obtained by multiplying the corresponding values of the maximum ground displacement and acceleration by the factors given in Table I of this guide. The displacement region lines of the Design Response Spectra are parallel to the maximum ground displacement line and are shown on the left of Figure I. The velocity region lines slope downward from a frequency of 0.25 cp' (control point D) to a frequency of 2.5 cps (control point C) and are shown at the top. The remaining two sets of lines between the frequencies of 2.5 cps and 33 cps (control point A). with a break at a frequency of 9 cps (control U.SAJEC REGULATORY GUIDES

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point B). constitut; the acceleration region of the horizontil Design Response Spectra. For frequencies higher than 33 cps. the maximumnt ground acceleration line repfc.ents the Design Rcptu.nw Spectra.

"flih vertical component Design Response Spectra

".orresponding to the maximum horizotd ground a'cekreuti's of 1.0 g are shown in Figure 2 of this guide.

The numerical values of design displacements, velocities, and accelerations in these spectra are obtained by multiplying the corresponding values of the maximum hJri:,ontal ground motion (acceleration = 1.0 g and displacement = 36 in.) by the factors given in Table II of this guide. The displacement region lines of the Design Response Spectra are parallel to the maximum ground displacement line and are shown on the left of Figure 2.

The velocity region lines slope downward from a frequency of 0.25 cps (control point D) to a frequency of 3.5 cpa (control point C) and are shown at the top.

The remaining two sets of lines between the frequencies of 3.5 cps and 33 cps (control point A), with a break at the frcquency of 9 cpa (control point B), constitute the acceleration region of the vertical Design Response Spectra. It should be noted that the vertical Design Respunse Spectra values are 2/3 those of the horizontal D'esiln Response Spectra for frequencies less than 0.25;

for frequencies lugher than 3.5, they are the same, while the ratio varies between 2/3 and I for frequencies between 0.25 and 3.5. For frequencies higher than 33 cpM. the Design Response Spectra follow the maximum pound acceleration line.

The horizontal and vertical component Design Response Spectra in Figures I and 2, respectively, of this guide correspond to a maximum horizontal ground acceleration of

1.0

.* For sites with different acceleration values specified for the design earthquake, the Design Response Spectra should be linearly scaled from Figures I and 2 in proportion to the specified maximum horizontal pound acceleration. For sites that (I) are relatively close to the epicenter of an expected earthquake or (2) have physical characteristics that could significantly affect the spectral pattern of input motion, such as being underlain by poor soil depxosts.

the procedure described above will not apply. In these cases, the Design Response Spectra should be developed individually according to the site characteristics.

C. REGULATORY POSITION

1. The horizontal component ground Design Response Spectra, without soil-structure interaction effects, of the SSE, 1/2 the SSE. or the OBE on sites underlain by rock or by soil should be linearly scaled from Figure I1 in proportion to the maximum horizontal pound acceleration specified for the earthquake chosen. (Figure I

corresponds to a maximum horizontal ground acceleration of 1.0 5 and accompanying displacement of

36 in.) The applicable multiplication factors and control points are gven in Table I. For damping ratios not included in Figure I or Table I, a linear interpolation should be used.

2.

The vertical component ground Design Response Spectra, without soil-structure interaction effects, of the SSE. 1/2 the SSE, or the OBE on sites underlain by rock or by soil should be linearly scaled from Figure 22 in proportion to the maximum horizontal grouMd acceleration specified for the earthquake chosen. (Figure

2 is based on a maximum hw algm d acdcrajn of 1.0 g and accompanying displacement of 36 in.) The applicable multiplication factors and control points are given in Table 11. For damping ratios not included in Figure 2 or Table 11, a linear interpolation should be used.

'This does not apply to sites which (1) an relatively com to the epcenter of an expected earthquake of (2) which haie physical characteristlca that couMd nifcantly affect the spectral ,rmbinatia of input motion. The Desip Respuotn Spectra for such sites should be developed on a cam-by-cam

1.60.2 K

DEFINITIONS

Respone Spectrum mcans a plot of the maximum response (acceleration. velocity. or displacemnct) of a family of idealized single-depee-of-fieekrcn damped oscillators as a function of natural frequencies (oi periods) of the oscillators to a specified vibratory motion input at their supports. When obtained from a recorded earthquake record, the. response spectrurr tends to be irregular, with a number of peaks ane valleys.

Design Resp..

Spectrum is a relatively smoot)

I

relationship obtained by analyzing. evaluating, and statistically combining a number of individual response spectra derived from the records of significant past earthquakes.

Maximum (peak) Ground Accderatio specified for a given site means that value of the acceleration which corresponds to zero period in the design resporse spectra for that site. At zero period the design response spectra acceleration is identical for all damping values and is equal to the maximum (peak) gpound acceleration I

specified for that site.

TABLE I

HORIZONTAL DESIGN RESPONSE SPECTRA

RELATIVE VALUES OF SPECTRUM AMPLIFICATION FACTORS

FOR CONTROL POINTS

Aenplificton Factors for Control Points of Acmalation" '

OiqImnment

Omanw0n A(33 qxl B(9 qx)

C42.5 cpd W)(0.2S qchI

0.5

1.0

4.96

5.95

3.20

2.0

1.0

3.54

4.25

2.50

S.0

1.0

2.61

3.13

2.05

7.0

1.0

2.27

2.72

1A88

10.0

1.0

1.90

2.28

1.70

Maximum gound disyacament is taken proportional to matmwm ground accelciation, and Is 36 In. for pround acceleration of 1.0 gravity.

sAbotimtion and displacement anplifkztion factor are taken from gecoiunmastions Stan in teforence 1.

1.60-3

VERTICAL DESIGN RESPONSE SPECTRA

RELATIVE VALUES OF SPECTRUM AMPLIFICATION FACTORS

FOR CONTROL POINTS

Perosnt Amplrification Fcitors for Control Points Critlcal Acooeratioo' 2 ai s

Daf*ping A(33 cps)

8(9 cps)

C13.5 cm)

D(0.25 cps)

0.5

1.0

4.96

5.67'

2.13

2.0

1.0

3.54

4.05

1.67

5.0

.0

2.61

2.98

1.37

7.0

1.0

2.27

2.59

1.25

10.0

1.0

1.90

2.17

1.13

'Maximum ground dispilacbment is taken proportional to maximum gound acceleration and is 36 in. ftw ground acceleration of 1.0 gravity.

s Acceleration amplhllation factors for the vcfti'al design response spectra arc equal to those for horizontal design re.sponse spcctra at a given frequency. whereas dixplacement ampltfcation f'actms are 2/3 those rot hod znnlal design response spectra. These ratios between the amplification factor for the two desia response spectra are In agreement with thou recommended n rceference I.

3Tbew values were changed to nake thb tabl consittsnt with the dis.

cussim of vertical cnmponents in Section B of this guide.

REFERENCES

I. Newnark. N. M.. John A. Blume. and Kanwar K.

Kapur, "Design Response Spectra for Nuclear Power Plants," ASCE Structural Engineering Meeting, Sin Francisco. April 1973.

2.

N. M. Newmark Consulting Engineering Services, "A

Study of Vertical SW- Horizontal Earthquake Spectra," Urbana, Illinois, USAEC Contract No.

AT(49-$)-2667, WASH-1 255, April 1973.

3.

John A. Blume & Associates, "Recommendations for Shape of Earthquake Response Spectra," San Francisco, California, USAEC Contract No.

AT(49-$)-301 I. WASH-1254. February 1973.

1.604 K

0.1

02

0.s

1

2

5

10

2D

50

100

FRr WUENCY. cps FIGURE 1. HORIZONTAL DESIGN RESPONSE SPECTRA - SCALED TO 1g HORIZONTAL

GROUND ACCELERATION

1000X

500

010e

4p I5

0.1

0D2

0.

1

2

5

10

20

50

100

FREOUENCY. cp, FIGURE 2. VERTICAL DESIGN RESPONSE SPECTRA - SCALED TO ig HORIZONTAL

GROUND ACCELERATION

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