ML13330A593
| ML13330A593 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/15/1985 |
| From: | Southern California Edison Co |
| To: | |
| Shared Package | |
| ML13311A380 | List: |
| References | |
| NUDOCS 8504180226 | |
| Download: ML13330A593 (46) | |
Text
SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 Technical Basis for Piping Strain and Stress Limits, Long Term Service Seismic Program Prepared by:
SOUTHERN CALIFORNIA EDISON COMPANY April 15, 1985 815041802 2 6 85041 PDR ADOCK 05000206 FD F DR
TABLE OF CONTENTS Section Pe TABLE OF CONTENTS
1.0 INTRODUCTION
1-1 2.0 BASIS FOR STRAIN LIMITS 2-1 2.1 Code Case N-47 2.2 Piping Component Testing Programs 2.3 Stress-Strain Curves 3.0 BASIS FOR STRESS LIMITS 3-1 3.1 Nonlinear Analysis 3.2 Piping System Testing Programs 3.3 Categorization of Seismic Loadings 3.4 Dynamic Versus Static Loadings 3.5 Operating Plant Earthquake Experience 4.0 APPLICATION PROCEDURE 4-1 REFERENCES R-1 APPENDIX A:
Comparison of LTS and SEP Criteria and A-1 Methodologies for Piping Analysis APPENDIX B:
List of Piping Materials and Allowable B-1 Stresses APPENDIX C:
List of RTS Piping First Natural C-1 Frequencies and Peak Spectra
1.0 INTRODUCTION
This document presents the criteria proposed for the qualification of large-bore (greater than 2 inch NPS) piping at San Onofre Nuclear Generating Station Unit 1 (SUNGS-1) under the Long Term Service (LTS) seismic review program.
In November of 1984, SONGS-1 was returned to commercial service after a lengthy outage. During the outage, many hardware upgrades were installed to increase the seismic capabililty of structures, piping and equipment.
The Nuclear Regulatory Commission (NRC) evaluated the adequacy of SONGS-i seismic design during the outage and issued a Safety Evaluation Report (SER) documenting their findings [1-1]. The NRC concluded that the Return to Service (RTS) structures, systems and equipment have been adequately designed and constructed to ensure public health and safety under a postulated 0.67 g Modified Housner Earthquake. Other systems were found to be adequate to withstand a 0.50 g Modified Housner Earthquake. The NRC approved the RTS design criteria and analysis methodologies for commercial operation for one fuel cycle. For the LTS program, however, the NRC has required that Southern California Edison (SCE) demonstrate the seismic capability of SONGS-1 according to criteria and methodologies suitable for long term station operation.
Recent discussions with the NRC, as part of the ongoing SONGS-1 LTS licensing process, have led to the generation of this document, regarding the justification of criteria proposed for the LTS qualification for large-bore piping.
Two qualification criteria have been proposed for LTS piping evluation, both based upon limiting piping system strain levels to ensure the piping remains functional. "Functional" piping, as discussed herein, is defined as piping with no significant decrease i n rated flow capacity. The two qualification criteria, as summarized in [1-2], are as follows:
The strain criterion - one percent strain limit for carbon steel and two percent strain limit for stainless steel.
The stress criterion - The elastically calculated piping primary stress, as defined in Equation 9 of the ASME Boiler & Pressure Vessel Code,Section III, Class 2/3 piping for Level D Service Condition, is to be compared to a stress limit of 2.0 times the yield strength (Sy) at the maximum operating temperature as follows:
PD M +M o 05i ab 4t+ 0.75 i
< 2.0 S Z
y where P
= Internal maximum operating pressure, psig Do
= Outside diameter of pipe, in.
t
= Nominal wall thickness of pipe, in.
Z
= Sectional modulus, in3 1 -1
i
- Stress intensification factor as listed in Figure NC-3673.2(b)-l of ASME B&PV,Section III, Subsection NC, 1980 Edition, Winter 1980 Addenda (This is the Code of Record for SONGS-1 Systematic Evaluation Program).
Ma
= Resultant moment due to gravity loads, in-lbs Mb
= Resultant moment due to 0.67 g Modified Housner Design Spectrum inertia, as calculated by linear elastic methods, in-lbs Sy
= Piping material yield strength at maximum operating temperature, psi (obtain Sy from Appendix I of ASME Code).
This applies to both carbon and stainless steel piping.
The first step in the evolution of the LTS piping functionality criteria is the establishment of acceptable piping strain limits. ASME Code Case N-47, numerous piping component testing programs and mechanical properties of applicable materials (stress-strain curves) form the basis for acceptable strain levels proposed for the SONGS-1 LTS program. At the proposed strain levels, the flow area reductions are acceptable for delivering rated flows. Code Case N-47 provides conservative allowable strains which may be applied to piping under low cycle dynamic loading.
As evidence of the conservatism included in the proposed strain criterion, we have proposed that Service Level D seismic load generated strains be compared to Service Level A, B, and C allowable strains as.
referenced in Code Case N-47. Numerous piping component testing programs support the conclusion that ductile piping will not deform to the point of impairing functionality under high seismic excitation. The mechanical properties of applicable materials are reviewed to further support the position that stainless steel should have a higher strain limit than the carbon steel. A detailed discussion justifying the proposed strain limits is presented in Secton 2.0.
The second step in the evolution of the LTS piping functionality criteria is the establishment of acceptable piping stress limits. The nonlinear analysis performed for SONGS-1 forms the basic position for the stress limit. In this nonlinear analysis, the allowable piping strains have been correlated to elastically calculated stresses (using ASME Class 2/3 stress intensification factor approach) in order to define allowable stresses for the LTS program. The primary goal of determining strain-correlated allowable stresses was to provide a measure of piping system acceptability for systems analyzed by practical, less costly linear elastic analysis methods, as opposed to requiring piping evaluations by nonlinear analysis methods. This allowable stress limit is further supported by piping system testing programs, categorization of seismic loadings, dynamic versus static loadings and operating plant earthquake experience. Piping system testing programs have confirmed that piping systems are able to sustain much higher stresses than the Code specified Level 0 allowables without plastic collapse, leakage or loss of pressure-retention capability. These testings and recent studies have formed licensing support for proposed elimination of the primary stress requirement for seismic loading on piping. On the conservative side, the proposed stress limit of 2.0 Sy does not take credit for the dynamic aspect of the seismic loading or the dynamic strain rate effect 1-2
on S
- The operating plant earthquake experience from a steam plant indicated that even for a conventional power plant without seismic supports, very little or no damage was observed under a severe earthquake (0.5 g). A detailed discussion justifying the proposed stress limit is presented in Section 3.0.
Section 4.0 presents a flow chart illustrating the application of the proposed strain and stress criteria for the SONGS-1 LTS seismic program.
Appendices A, B, and C have been included to provide a clearer perspective of the impact of applying these criteria at SONGS-1.
Appendix A summarizes the differences between the proposed LTS criteria and methodology versus the previously licensed Systematic Evaluation Program (SEP) criteria and methodology for SONGS-1.
Appendix B summarizes material properties for all applicable materials at SONGS-1, comparing SEP allowable stress versus LTS proposed allowable stress.
Finally, Appendix C provides a summary of piping system natural frequencies and peak spectra accelerations and frequencies for those systems analyzed by linear elastic stress methods during the SONGS-1 RTS program.
1-3
2.0 BASIS FOR STRAIN LIMITS 2.1 Code Case N-47 Code Case N-47 [2-2] addresses the design and analysis of. Class 1 components at elevated temperatures. Elevated temperatures are defined as temperatures exceeding those covered by the rules and stress limits of ASME Subsection NB and the tables in Appendix I. At these high tempera tures, creep effects may become significant and the stress criteria are not appropriate. The rules of the Code Case guard against deformation related failures, such as:
o Creep rupture from long term loadings o
Creep fatigue failure o
Loss of function due to excessive deformation o
Gross distortion due to incremental collapse and racheting.
Appendix T of Code Case N-47, "Rules for Strain, Deformation, and Fatigue Limits at Elevated Temperatures" provides the following strain limits for Service Levels A, B and C loadings (corresponding to Normal, Upset and Emergency conditions, respectively):
1 percent Averaged through thickness (membrane) 2 percent Surface strain due to a linearized distribution through the thickness (membrane plus bending) 5 percent Local strain at any point.
Although the strain criteria in the Code Case were developed for use at elevated temperatures, where stress criteria cannot be applied, the strain criteria can also be applied to the dynamic analysis of components at lower temperatures. In fact, Rodabaugh [2-3] refers to.the Code Case N-47 strain limits in a discussion of Code Stress limits and inelastic analyses, including seismic analyses. In addition, strain limits for Service Level D (Faulted condition) loadings are not specified in Code Case N-47. The use of strain limits specified for Service Levels A, B and C loadings for the 0.67g Modified Housner Design Spectrum loading (Faulted condition) is conservative.
The strain limits presented provide assurance of the structural integrity of the piping and limit gross distortion (which is the phenomenon addressed in the seismic evaluation).
The limits presented in the Code Case were developed for inelastic analysis methods, since elevated temperature conditions often result in stresses above the elastic range.
Therefore, the strain limits which are developed in the Code Case, to address creep and elevated temperature effects are applicable for use in the seismic evaluation for SONGS-1.
The classification of stress intensities, and therefore the classifica tion of strains, is given in Tables 2-1 and 2-2 which are taken from Table-3217-2 of Code Case N-47 and Table NB-3217-2 of Section III, Subsection NB, respectively. A review of the tables shows that only 2-1
internal pressure causes general membrane (Pm) stresses and strains.
Thus, the 1 percent limit is only applied to the portion of the strain caused by internal pressure. Stresses and strains due to mechanical loads, including gravity and seismic loading, are classified as local membrane (PL) plus bending (Pb).
Therefore, the 2 percent strain limit for local membrane plus bending is applicable to seismic loading.
2.2 Component Testing Programs Numerous experimental studies have been carried out to investigate the behavior of critical components of piping systems. Results of three studies are described below in detail.
The first study by Imazu [2-4]
evaluated five stainless steel elbows under static loads. In the second study, Greenstreet [2-5] tested four stainless steel elbows statically.
In the third study, Teidoguchi [2-6] performed static and dynamic tests on stainless steel elbows.
Imazu Test Results Imazu performed plastic instability and buckling tests on five thin-walled stainless steel elbows. The elbows were 12 inch Schedule 10S and 20S long radius elbows made from Type 304 stainless steel.
The elbows were loaded statically in both in-plane and out-of-plane directions to, and past, the plastic instability point using displacement controlled techniques.
The results from these tests demonstrate that strains of up to 2 percent resulted in an ovality of the cross-section which corresponds to a flow area reduction of five percent. This five percent flow area reduction occurs only at a local point in the piping system and would have an insignificant overall effect on pipe rated flow.
It should be noted that these tests were performed on thin-walled, non-pressurized elbows at elevated temperatures (6000C).
For SONGS-1, stainless steel elbows are thicker, are pressurized, and are at much lower temperatures than those tested by Imazu. Therefore, the Imazu elbow test results represent a conservative bounding case for SONGS-1 application.
Greenstreet Test Results Greenstreet determined the plastic deflection responses of four 6-inch Schedule 40S and 80S commercial stainless steel (SA312-304L) elbows subjected to external static in-plane bending moment without the application of internal pressure. Tests were carried out to the maximum capacity of the testing apparatus which provided the limitations to the test's recorded response. In all the cases, there was no indication of failure or gross structural instability.
Ibrahim and Kitz [2-7]
demonstrated that these results correspond to elastically calculated piping stresses well beyond the Code Level D limits.
2-2
CASES OF ASME BOILER AND PRFSSURE VESSEL CODE Table -3217-2 Classification of Stress Intensities in Piping, Typical Cases Discontinuities Considered Piping Component Locations Origin of Stresses Classification' Gross Local Pipe or tube, elbows, and Any, except crotch regions Internal pressure No No reducers. Intersections of Intersections PL and Q Yes No and branch connections F
Yes Yes except in the crotch Sustained mechanical loads Pb No No regions including weight PL and Q Yes No F
Yes Yes Expansion Pm, Pb and Q-*
Yes No F
Yes Yes Axial thermal gradient Q1 Yes No F
Yes Yes Intersections, In the crotch region Internal pressure, sustained PL and Q3 Yes No including tees mechanical loads and F
Yes Yes and branch expansion connections Axial thermal gradient Q3 Yes No F
Yes Yes Bolts. and Any Internal pressure, gasket PM No No flanges compression, bolt load Q
Yes No F
Yes Yes Thermal gradient Q1 Yes No F
Yes Yes Expansion PmP6 and Q"*
Yes No F
Yes Yes Any Any Nonlinear radial thermal F
Yes Yes gradient Linear radial thermal gradient Q'
Yes No 1 These classifications may be modified for purposes of certain criteria in Appendix T.
'See -3138 and -3213.8.
'Analysis is not required when reinforced in accordance with -3643.
Table 2 Stress Classifications, Excerpted from ASME Code Case N-47 2-3
TABLE NB-3217-2 CLASSIFICATION OF STRESS INTENSITY IN PIPING, TYPICAL CASES Discontinuities Considered Piping Component Locations Origin of Stress Classification Gross Local Pipe or tube, elbows, and Any, except crotch regions Internal pressure P.
No No reducers. Intersections of intersections PL and Q Yes No and branch connections F
Yes Yes except in crotch regions Sustained mechanical loads, PNo No including weight P, and Q Yes No F
Yes Yes Expansion P.
Yes No F
Yes Yes Axial thermal gradient Q
Yes No F
Yes Yes Intersections, In crotch region Internal pressure, sustained P, and 0 [Note (1)]
Yes No including tees mechanical loads, and F
Yes Yes and branch expansion connections Axial thermal gradient 0
Yes No F
Yes Yes Bolts and Any Internal pressure, gasket P,,,
No No flanges compression, and bolt load Q
Yes No F
Yes Yes Thermal gradient Q
Yes No F
Yes Yes Expansion P.
Yes No F
Yes Yes Any Any Nonlinear radial thermal F
Yes Yes gradient Linear radial thermal gradient F
Yes No Anchor point motions, including Q
Yes No those resulting from earthquake NOTE:
(1) Analysis is not required when reinforced in accordance with N B-3643.
Table 2 Stress Classifications, Excerpted from Subsection NB 2-4
Teidoguchi Test Results The experimental study by Teidoguchi included extensive testing to justify the functional capability of Class 1 stainless steel elbows.
Static and dynamic tests were performed at room temperature. The static tests were performed with an external force large enough to produce a predominantly plastic response. The load deflection curves reported from the study indicated that the tests were conducted up to a strain level of 2 percent (which corresponds to ten.times the proportional limit). At these strain levels, geometric and structural stability of the components were maintained.
The dynamic tests reported for elbow piping components were for a 3 inch (L.R.) lightwall elbow welded to a 3 inch Schedule 40 pipe. The material of these elbows was SUS27TP, which is equivalent to the ASME stainless steel TP-304. The piping system was supported on a shaker table and subjected to harmonic excitation. The amplitude of the dynamic moments and the number of cycles till leakage were recorded. Corresponding piping stresses were calculated, ranging from a maximum value of 6.2 to a minimum value of 2.9 times the ASME Class 1 Level D limits. These ratios were derived by applying the Class 1 stress indices approach and the 3.0 Sm allowable, which is approximately equal to 2.0 Sy. The moments derived from tests were not adjusted for the difference in the specimen material strength and that specified in the Code. The results also showed that internal pressure improves the functional capability of the designed elbows under dynamic loading.
2.3 Stress-Strain Curves Stainless steel piping materials are significantly more ductile than carbon steel materials and thus have a significantly greater inherent reserve capacity. This can be shown from the comparison of typical mechanical properties at room temperature as follows [2-8].
Tensile Yield Ultimate Reduction Brinell Strength Strength Elongation of Area No.
Ksi Ksi Mild Carbon Steel 50-65 30-40 25-40 120 Stainless Steel 85-95 30-35 55-70 65-75 145-160 18 Cr - 8 Ni (Type 304)
Figures 2-1 and 2-2 are engineering stress-strain curves for mild carbon steel (0.25 carbon) and stainless steel (Type 304), respectively, from
[2-9] and [2-10]. At the tensile (or ultimate) strength, carbon steel exhibits approximately 25% strain while stainless steel exhibits approximately 70% strain.
2-5
All of the above results support the acceptability of a strain limit of 2 percent for stainless steel materials. This allowable limit. will ensure structural integrity as well as no loss of functionality due to significant flow area reduction.
2-6
Cwve 1, Stroin, in. per i.
0 0
Curve I Ultimate strength Severe neckin b/bYield oin?
Curve 31 c
.r
/0 Proportional limnit 508 8
-8 0
00 o
o 0
0 Strain, In.
per 20.
Curve 31. Yied point region, Strain, in pe in Fig 2-1: Engineering Stress-Strain Curve for Mild Carbon Steel 800 1006 2
400 80 4 0 C
-200 20 0w 0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 O
Engineering Strain Fig 2-2:
Engineering Stress-Strain Curve for Type 304 Stainless Steel 2-7
3.0 BASIS FOR STRESS LIMITS 3.1 Nonlinear Analysis The purpose of the nonlinear analyses performed for SONGS-1 [2-1] was to show that typical piping systems remain functional (i.e., below the 1 and 2% strain limits) at an elastically calculated intensified stress limit of 2.0 S y* The load combination considered in the analysis was pressure, gravity and seismic inertia.
Numerous hot safe-shutdown piping systems were reviewed and two representative piping systems (AC-19 and MW-01) were selected for the study. The two systems provided a good representation of the various piping components, materials, and system types represented in the plant.
Both carbon and stainless steel materials were considered, as well as piping components of different sizes and flexibilities. Both systems have typical run configurations with a mix of various component types.
Although the design response spectra did not produce seismic stress levels in the system at the functionality stress limit of 2.0 S. input motions were increased to produce the desired maximum elastic stress in the most highly stressed portion of the system. (The elastic stresses are calculated based on the ASME Class 2/3 stress intensification factor approach.)
Elastic analyses were performed for gravity and seismic inertia to provide results for comparison with the results from nonlinear analyses.
This ensures proper development and accuracy of the nonlinear analysis model.
To maintain functionality, (i.e., to deliver the rated flow) the elbow, tee and straight pipe components must not distort excessively (ovalization). The ANSYS computer program was used for the nonlinear analyses. Models were developed with elbow and tee components which closely matched experimentally verified behavior (see attached nonlinear analysis models, Figures 3-1 and 3-2).
The time history loading used to develop the elastically calculated stress of 2.0 S (the study.used limits of 2.0 S for carbon steel and 2.2 S for stainless steel) at critical components (elbow for both systems was input for the nonlinear analysis. The strains calculated from the nonlinear analysis were correlated with the stresses calculated from the elastic analyses with the same input. As shown in the attached Tables, 3-1 and 3-2, the strains were less than 1 percent for carbon steel and less than or equal to 2 percent for stainless steel.
These strain levels were used to compute maximum ovalization. At these strain levels, maximum ovalization and flow rate reductions were considered to be acceptable (less than 5 percent flow area reduction).
A major conservatism in the nonlinear analyses was the material law assumed for the ANSYS model.
The moment-deflection curves used on the ANSYS model match closely with experimental data; thus, the proper global response was assured. Additionally, by matching the moment-deflection curves, a conservative moment-strain relationship was produced. This can be seen by reviewing the attached Figures, 3-3 and 3-4. For example, a 3-1
moment of 200 in-kips produces deflections of approximately 0.35 inches in both the ANSYS and experimental studies (Figure 3-3).
However, this same moment produced experimental strains of 0.16 percent while the ANSYS model predicted 0.45 percent (Figure 3-4).
Thus, the ANSYS-calculated strains are greater than those reported in experimental studies.
Other conservatisms in the analysis are as follows:
o Code-specified minimum material strengths were used in the analyses. Actual material strengths are greater than Code-specified minimums.
o Nominal component thicknesses were used on the analysis. Component thicknesses are normally greater than nominal values. This increases the strength and moment-carrying capacity of the components.
o Strain rate effects which enhance yield strength are neglected.
o Pressure effects increase collapse moments of components. These effects were neglected in the analysis.
In summary, this study conclusively demonstrates that an elastic piping stress limit of 2.0 Sy for carbon and stainless steel piping systems provides assurance that the piping systems will still perform their function. This criterion allows local yielding in components such that load redistribution reduces maximum moments and stresses, yet provides limits on the extent of yielding such that functionality of the system is maintained.
Similar nonlinear analyses have also been performed at Commonwealth Edison's Dresden and Quad Cities Plants to successfully license the 2.0 Sy stress limit as part of their IE Bulletin 79-14 program [3-1].
3-2
TABLE 3-1 AC-19 Nonlinear Analysis Results - Strains (From Table 5.6 of Reference [2-1])
Linear Analysis Nonlinear Analysis Location (See Figures 5.1)
Stress, ksi Maximum Strain, Percent Elbow 1 @ Node 2 49.7 0.49 Elbow 2 @ Node 7 39.6 Remained Elastic Elbow 3 @ Node 8 69.4 (2.0 S, (1))
0.74 Pipe @ Node 14 53.8 0.21 Pipe @ Node 16 77.5 (2.2 Sy (1))
0.41 Tee 1 86.6 (2.5 Sy (1))
Remained Elastic Notes: (1) S = 34.7 ksi y
3-3
TABLE 3-2 MW-01 Nonlinear Analysis Results - Strains (From Table 5.10 of Reference [2-1])
Linear Analysis Nonlinear Analysis Location (See Figures 5.2)
Stress, ksi Maximum Strain, Percent Elbow 3 @ Node 8 23.1 0.10 Elbow 4 @ Node 14 55.0 (2.2 Sy (1))
2.0 Elbow 4 @ Node 16 31.8 0.42 Pipe @ Node 19 38.9 0.07 Tee 1 90.8 (3.6 S, (1))
Remained Elastic Notes:
(1) S
= 25.0 ksi 3-4
xo 3-5
di-.1 CAA o
-o FIGURE 3-2 MW-01 Mathematical Model - Nonlinear Analysis (From Figure 5.2 of Reference [2-1])
3-6
c035 (A)
-n I
' -4
-ni
- D ANSYS (0
C) 300 EXPERIMENTAL C0~
300/
(D (D 0 (D
~
250
=C+
(DC(D'
(
CD zLOAD APPLIED PERPENDICULAR I 200 TO PLANE OF ELBOW 6" SCH 40 L.R.
ELBOW CARBON STEEL 150 0
CD 100
=
501 C
0.25 0.50 0.75 1.00 1.25 DEFLECTION, IN
co C-.
Example: For a moment of 200 in-kips, experimental study predicts 0.16% strain; ANSYS predicts 350 0.45% strain.
EXPERIMENTAL 300 efl Ca
(
OD 250 0
CD C
CD) no.1%.45%,
ANSYS (DO(
o 150 LOAD APPLIED PERPENDICULAR TO PLANE OF ELBOW f
6" SCH1 40 L.R. ELBOW 100
/CARBON STEEL 05 C
(D 0.1 0.2 0.3 0.4 0.5
- STRAIN, PERCENT
3.2 Piping System Testing Programs The U.S. Nuclear Regulatory Commission and the Electric Power Research Institute have jointly sponsored a piping research program involving the design, analysis, fabrication, erection, and dynamic testing of prototypical piping systems [3-2]. One objective of this program was to stimulate recognition of safety margins implicit in ASME B&PV Code rules for Classes 2 and 3 piping by demonstrating the existence of large design margins in piping and support systems when subject to seismic loads much greater than those acceptable according to the ASME Code.
Results from this effort and other similar experimental programs [3-3, 3-4 and 3-5] have confirmed that piping systems are able to sustain extreme dynamic loads without plastic collapse, leakage, or loss of pressure-retention capability. Results of these programs demonstrate that piping systems have large inherent reserve margins under seismic loading.
These programs have generated proposed changes to the ASME Code requirements that would remove seismic loading from a primary stress check in Code Equation 9 [3-6] (see Section 3.3 for detail discussions).
Below, we briefly discuss two of the recent testing programs for piping systems, performed by ANCO [3-2]. The first system consists of a 70 ft.
long, six-inch Schedule 40 pipe run. The piping was subjected to accelerations as high as 15g and response accelerations over 50g were measured. The second system consists of a 20 ft. long, four-inch, Schedule 40 pipe run. Accelerations as high as 14g were input and response accelerations greater than 21g were measured.
a) 70 ft. Long, 6-inch Diameter, Schedule 40 Piping System The first piping system tested was a single run of A106 B carbon steel about 70 ft. long. It is shown in Figure 3-5. Six-inch, Schedule 40 and eight-inch, Schedule 40 piping was employed, with the larger diameter pipe located at the ends of the pipe run. The 6-in. and 8-in. pipe were joined together using standard 6 x 8 reducers. The pipe elbows were 90* long radius elbows. The piping was designed following ASME Code rules.
Comparison of analytical and test frequencies of this piping system is shown in Table 3-3. The first natural frequency is 4.18 and 4.62 Hz from analysis and test, respectively.
Multiple tests were conducted with various magnitudes of dynamic input and support configations. The piping was pressurized to 1150 psig and driven with a 20 second input earthquake time history.
Selected test results are shown in the table below:
3-9
INPUT MAX. EXP.
RATIO TO
- RATIO TO **
MAX.
TEST CASE ZPA(G)
STRESS (KSI)
ASME LEVEL D Sy STRAIN %
1 (XEQ3Cl) 2.24 32.4 0.9
.93
.0677 2 (XEQ1) 4.32 42.12 1.17 1.2
.0953 3 (XEQ2) 4.86 47.16 1.31 1.35 0.1040 4 (XEQ3) 5.38 47 52 1.32 1.36 0.1070 5 (YEQ1) 4.33 65 88 1.83 1.88 0.1153 6 YEQ2) 5 55 74.52 2.07 2.13 0.1312 7 YEQ3) 1.75 65.16 1.81 1.B6 0.1100 8 (YEQ4) 8.38 83.52 2.32 2 39 0.1400 Maximum Experimental Stress/2.4 Sh
- Maximum Experimental Stress/S The maximum experimental stresses were calculated, using the stress intensification factor approach of the ASME Code for Class 2 piping (1980 Edition).
From this table, it is observed that at just below Level 0 Stress (Test Case 1), the maximum measured strain in the piping was 0.06 percent. The maximum input acceleration for this case was 2.24g. Test Case 6 shows that at a stress level corresponding to 2 times Level D (or 2.13 Sy for the pipe material) the maximum measured strain was 0.13 percent. The maximum input acceleration was 5.5g for this test case. Test Case 8 shows that for a stress level corresponding to 2.39 Sy, the maximum measured strain in the piping was only 0.14 percent.
These experimental results show that low strains are obtained at stress levels greater than 2.0 S Y. Thus, a stress limit criteria of 2.0 S y is conservative.
To show the severity of the input for a particular test case, the input response spectrum for Test Case 6 is compared in Figure 3-6 to the input required to just achieve the Level D stress condition in the piping system of Test Case 1. This test was about a factor of four greater than the input necessary to match the Level 0 stress limits in the frequency region of interest for the first piping system. That is, the piping system successfully withstood an earthquake input about four times greater than the Code design rules would indicate to be acceptable. The piping system, in fact, withstood several more severe dynamic tests with no gross distortion or loss of pressure retaining capacity.
b) 20 ft. Long, 4-inch Diameter, Schedule 40 Piping System The second piping system consisted of a prototypical nuclear power plant piping segment which was tested by ANCO Engineers Inc., under EPRI sponsorship, to determine its ultimate dynamic load capacity.
The selected piping was a 20-foot run of 4-inch, Schedule 40 ferretic material with two elbows and three supports. An earthquake-like dynamic input was specified at each one of these supports. The piping tested is shown in Figure 3-7.
3-10
The piping run was designed in accordance with ASME Code Class 2 rules and was dynamically excited to varying response levels while under the Code maximum allowable internal pressure.
Figure 3-8 shows the horizontal dynamic spectra imposed on the piping. Also shown in Figure 3-8, for comparison purposes, is an SSE response spectra for a typical nuclear power plant. As may be seen, the test spectra input to the piping is seven to eleven times the SSE spectra in the frequency range of importance to the tested piping system (approximately 6 to 13 Hz.).
That is, the imposed horizontal seismic-like input to the piping was roughly an order of magnitude greater than that typically used in the design of nuclear power piping.
The first and second test frequencies of this piping system are 6 and 13 Hz, respectively.
Figure 3-9 is a comparison of the actual input test spectra with a spectra which produced stresses in the piping system equal to Code allowable (2.4 Sh). It is observed that the dynamic input to the test resulted in elastically calculated stressed, using the stress intensification factor approach of the ASME Code for Class 2 Piping (1980 Edition) equivalent to 4.0 S.
This stress level corres ponds to 3.3 times the Code allowa le stress 2.4 Sh.
At stress level of 4.0 S, no leakage occurred. Permanent deformations in several region of the piping were observed, but there was no plastic collapse or loss of structural integrity in the pressurized piping, even with the extreme seismic input.
Based on the test data reported and strain levels achieved the 2.0 S stress limit represents a conservative, yet realistic criteria for piping systems at SONGS-1.
3-11
Table 3-3:
Comparison of Analytical and Test Frequencies for 70-ft.
Long, Six-inch, Schedule 40, Piping System Analytical Direction of Analytical Test Test Mode Max. Component Freq.
Freq.
Mode No.
Of Eigenvector (Hz)
(Hz)
No.
1 Y
4.18 4.62 1
2 Y
6.76 7.11 2
3 Z
8.66 2
4 X
8.70 9.16 3
5 X
11.57 11.66 4
6 X
14.53 13.54 5
7 Z
16.24 8
Z 16.65 9
X 17.86 17.71 6
18.53 7
10 Z
21.68 11 Z
24.24 23.94 8
12 X
25.72 25.87 9
13 Z
28.96 28.06 10 29.30 11 3-12
NOTES RADIUS OF CURVATURE OF ELBoWS -
S*
(EXCEPT AS NOTED)
SCH40 8-X6-REDUCER EL.
IIle C
ItI zELDING FLANGE 3-13 10',RADIUSFANG 3--83
NRC/EpRI 1 CO4IC 5 Y FCRCNG EARTHQUAKE 2 CA 1707 C
51 Y C
CHANNEL 14 DALVINC 0.030 2011111 1
I lI I
l I
I il K-Test Input Spectrum
- -- Level D Spectrum 1312 Microstrain Peak 645 Microstrain 1
'St.
94 0
I 3-1
- o.
Iotoc Level 06AlloicleoStrrsie 3-44f
4.0 3.0
.23.1 z
2.2 2.1 1.4 1.6 2.0 e.Wld Location 1.0 Pinned Supports at Pta. 1.0 and 4.0 Variable Support at Pt. 1.4
- Actuators at Pta. 1.0, 1.4, and 4.0 FIGURE 3-7 Geometry for 20 ft. Long, 4 inch Diameter Piping System 3-15
ANCO ENGINEERS Test 9 1
Run a 5
Time 15:20 Date 9/22/8lRecorded by KB Page _
Test Specimen:
EPRI pipe test specimen la Purpose of Test:
attempted, 800% cif yield test Direction:
tZ Comments:
Channel 3 Response Spectra for piping input, Damping = 2%
point 1.0 r-rn Horizontal Response Spectra for plant sited in Southeast U.S.A. for safe shutdown earthquake F l
-8 eting ecta for 2 ft. Lon g inc D i at Pi in rgl 1
)*a.sAAyVNKe.
System, Compared to That for a Typical Nuclear Power Plant 3-16
Ng'0 I"GIF.N Test F 1
Run 1 5
Time 15: 20 Date 9/ 2 2/ 8 1Recorded by KB Page I Test Specimen:
EPRI pipe test specimen la Purpose of Test:
attempted 800% of yield test Direction:
tZ Comments:
Channel 3 Damping = 2%
STest Spectra Spectra to Generate Maximum Acceptable Stress. Condition FIUR 3-Y Tesin Spcr fo 20 ft. Log/IchDamtr Pipin ADN
- SO*
Syste Compaed toN T A Whic Wol Prouc L
Y\\
X AllowableuStresses 3-17
3.3 Categorization of Seismic Loadings In current ASME Code rules, seismic inertia stress is categorized as the primary stress and evaluated in Code Equation 9 as follows:
Class 1 piping:
PDD (Level D)
B
_2+8
-o i
3m(LvlD 1 2t 221 Class 2/3 piping:
PDo + 0.75 i (Ma + MB) h 2 4 Sh (Level D) 4t Z
The 1980 edition of the Code for Class 1, 2 and 3 piping is used for the above equations and all terms are defined in the Code.
Studies have been performed, or are in progress, to investigate the licensing support for the elimination of the primary stress requirement for seismic loading on piping. E.C. Rodabaugh stated in [3-6] that because of the limited energy input of earthquakes to piping systems, it may be that earthquakes will not produce gross plastic deformation of piping systems. The EPRI/ANCO piping tests [3-3] also suggested that the real failure mechanism for earthquakes is not the formation of primary collapse mechanisms, but is fatigue-related. A logical consequence of these studies is to remove moments due to earthquakes from Code Equation 9 and perform a separate low cycle fatigue evaluation. For example, E.C.
Rodabaugh recommended in [3-6] that the allowable faulted stress ranges due to SSE should be up to 4.5 Sm for carbon steel and 7.9 Sm for stainless steel.
If seismic inertia stress is categorized as the non-primary stress, the 2.0 S allowable for pressure, gravity plus inertia loadings represents a coervative primary stress limit because SSE inertia is the dominant loading of the three.
3.4 Dynamic versus Static Loadings Current ASME Code elastic analysis stress response acceptance criteria do not differentiate between dynamic (such as seismic) and static loading events. It is well known that structures can withstand much greater loads if the loads are dynamic in nature; i.e., cycled on and off the structure. Since the ASME Code is based entirely upon the static strength of components, there is a seismic reserve margin associated with neglecting the dynamic aspects of the loading. Reference [3-7] describes one major study to quantify this margin in the particular case of nuclear power plant piping systems. The results show that a dynamic load must be, on the average, 1.52 times a static load in order to produce the same stress and strain levels that are currently allowed by the ASME Code for Service Load D conditions (i.e., loads which include the design basis earthquake).
3-18
Also, materials testing procedures are based upon the-pseudo-static application of loads (i.e., the loads are applied to the specimen at a very slow rate). It is well known that higher rates of loading result in an increase in the yield stress of the material - a phenomenon termed the dynamic strain-rate effect. Since the ASME Code considers both static and dynamic loadings, the specified minimum yield stresses are based upon the lower values appropriate for static cases. Reference [3-8] shows that the strain rate effects associated with seismic loading would result in a minimum increase in material yield strength of 11 percent. Figure 3-10 shows the effect of strain rate on yield streqgth of mild steel
[3-9]. For example, at a strain rate of 2.5 x 10-in/in/second (which corresponds to the piping fundamental natural frequency of 6 H ), the increase in yield strength over the static yield strength is a~out 15 percent.
In establishing the allowable stress limit 2.0 S for the Code.Equation 9, the benefit associated with the dynamic aspects of the seismic loading, as well as the dynamic strain-rate effect is conservatively.
neglected in piping analysis.
3-19
00
_I_
OO_
I 90 80 70 60 U) wL 50 U,
10-6 os 10-'
I0-I0C2 I-10 102 I0 AVERAGE RATE OF STRAIN PER. SEC.
FIGURE 3-10 Relationship Between Material Yield and Strain Rate for Mild Steel (Reference [3-9])
3-20
3.5 Operating Plant Earthquake Experience The El Centro Steam Plant was inspected by an NRC team following the October 15, 1979 Imperial Valley Earthquake [3-10]. The inspection was of interest to the NRC because the plant is similar to older operating nuclear power plants in both design and types of equipment installed.
The NRC team observed only minor damage to the plant's structural and mechanical systems despite the estimated O.5g peak horizontal ground acceleration produced at the site.
The large magnitude earthquake had its epicenter on the Imperial Fault, approximately 15 miles from the plant. When the earthquake occurred, Units 3 and 4 of the four-unit nonnuclear plant were operating. The operating units tripped off-line when the station's power was lost.
Unit 3 was restored to service within 15 minutes after the main shock. Unit 4 was restored to service within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
The plant's original design criteria specified a static lateral load equivalent to 20 percent of the dead and live loads. Following the earthquake, the NRC engaged LLNL to analyze Unit 4 [3-11]. To accurately predict the actual response of the Plant from the earthquake, the LLNL study used realistic assumptions for the analysis, thus eliminating many of the conservatisms that are used in the analysis of nuclear power plants. For example, in the soil-structure interaction analysis, soil damping ratios as high as 100 percent of critical were used. The use of these highly damped soil springs provided a reasonable estimation of the forces induced in the structure as evidenced by the close relationship of the observed to the predicted base shears. It should be noted that for SONGS-1, the soil damping was limited to a maximum of 20 percent of critical, when in fact, experimental testing supported the use of damping as high as 50 percent of critical. It is reasonable to conclude that as a result of limiting the soil damping alone, we are severely overestimating the response of SONGS-1 structures, piping and equipment.
The LLNL study concluded that the forces experienced by the plant equipment were on the order of 2 to 9 times greater than the O.2g specified design load. The reserve seismic capacity in-the plant equipment is then at least of the order of 100 percent. Note that because of the highly damped soil properties used in the SSI analysis, the forces calculated from analysis represent a low estimate, if compared with the forces that would be obtained using more conservative assumptions, as was done for SONGS-1.
The reserve margin would be even greater if analysis techniques such as used for SONGS-1 were used.
The above conclusion was confirmed by observations of the actual response of piping systems at the plant. Post-earthquake inspection indicated that no high-temperature or high-pressure piping failed during the earthquake. Piping failures were observed only.in two lines, at locations that had been either weld-repaired or had been excessively corroded.
3-21
We can conclude that operating nuclear power plant structures, equipment and piping, such as those in SONGS-1, have considerable seismic reserve margins capable of sustaining an earthquake which far exceeds its nominal design capacity.
3-22
4.0 APPLICATION PROCEDURE The application procedure of the two criteria for LTS large-bore piping qualification can be summarized as follows:
Step 1 Perform piping analysis using piping computer code SUPERPIPE and check the ASME NC/ND-3600 Equation 9 (Level D) stresses against the allowable 2.0 Sy (the stress criterion). Other Code equations will also be checked against appropriate Code allowables. If piping is qualified, then go to step 2. If piping is not qualified, add more supports.
Step 2 Perform support evaluations using the NRC approved support criteria and methodology for the LTS. If supports are not qualified, then perform piping reanalysis without these failed supports, using either the stress criterion (go back to Step 1) or the strain criterion (go to Step 3).
The strain criterion will be used only if there is a single support failure. The definition of a single support failure is that at least two neighboring supports in the same restraint direction as the failed support, and on both upstream and downstream sides are qualified.
Step 3 Perform energy balance hand calculation using the strain criterion. If piping is not qualified, add more supports. A detailed discussion of the energy balance method is summarized in a separate report to the NRC titled "Energy Balance Method for Piping Systems."
This procedure is illustrated in a flow chart in Figure 4-1.
4-1
STEP 1 Piping Analysis Stress Criterion: ASME NC/ND-3600 Equation 9 (Level D) <-2 Sy STEP 2 Support Evaluation LTS Support Criteria and Methodology If Support Failure For Multiple Supports Failure
-For Single Support Failure STEP 3 Piping Analysis Strain Criterion:
1% for Carbon Steel 2% for Stainless Steel FIGURE 4-1 Application of the Stress and Strain Criteria for Large-Bore Piping 4-2
REFERENCES
[1-1]
"Safety Evaluation Report of the Return To Service Plan, San Onofre Nuclear Generating Station, Unit 1," Docket No. 50-206, NRC Letter to SCE, dated November 21, 1984.
[1-2]
SCE Report No. 01-0310-1368, "San Onofre Nuclear Generating Station Unit 1 Seismic Program for Long Term Service," Submitted to NRC on March 8, 1985.
[2-1]
Impell Report No. 04-0310-0063, "SONGS-1 Functionality Criteria for Piping Systems in Response to the DBE Event," Revision 2, December 1983 (Transmitted to NRC in SCE Letter to NRC, from K. Baskin to D.M. Crutchfield, dated December 23,1983).
[2-2]
ASME Boiler & Pressure Vessel Code, Case N-47-21, "Class 1 Components in Elevated Temperature Service,Section III, Division I," approved December 11, 1981.
[2-3]
Rodabaugh, E.C., "Postion Paper on Stress Allowables for Piping,"
included on NUREG-106, Report of the U.S. Nuclear Regulatory Commission Piping Review Committee Evaluation of Other Loads and Load Combinations.
[2-4]
Imazu, Sahahibara, Nagota and Hashimoto," Plastic Instability Test of Elbows Under In-Plane and Out-of-Plane Bending," Paper E6/5, Sixth SMIRT Conference, Paris, France, August 1981.
[2-5]
Greenstreet, W.L., "Experimental Study of Plastic Response of Pipe Elbows," ORNL/NUREG 24, February 1978.
[2-6]
Teidoguchi, H., "Experimental Study on Limit Design for Nuclear Power Facilities During Earthquake," Japanese Report 50-1705 Issued to U. S. NRC, February 1975.
[2-7]
Ibrahim, Z.N, Kitz, G.T., "Evaluation of the Functional Capability of ASME Section III Class 1, 2, and 3 Piping Components," ASME Paper 78-PVP-83 and Sargent & Lundy Engineers Report No. GEX 5750-00, June 1978.
[2-8]
Marks' Standard Book for Mechanical Engineers, 7th Edition
[2-9]
Harvey, John F., "Pressure Component Construction"
[2-10]
EPRI NP-2347, "Instability Predictions for Circumferentially Cracked Type-304 Stainless Steel Pipe Under Dynamic Loading", Volume 2, April 1982.
R-1
REFERENCES (continued)
[3-1]
Impell Report No. 01-0590-1355, "Quad Cities Unit 1 Functionality Study of Piping Systems in Response to the SSE Event", Revision 0, December 1980.
[3-2]
NUREG/CR-3893, "Laboratory Studies:
Dynamic Response of Prototypical Piping Systems", Prepared by ANCO Engineers, Inc. for the USNRC and EPRI, August 1984.
[3-3]
EPRI Report No. NP-3746, "Dynamic Response of Pressurized Z-Bend Piping Systems Tested Beyond Elastic Limits and with Support Failures", Prepared by ANCO Engineers, Inc. for EPRI, December 1984
[3-4]
Sand, Lochan, Schoor, and Hass, "Experimental Study of Dynamic Behavior of Piping Systems Under Maximum Load Conditions Analysis," Kraftwerk Union, Federal Republic of Germany, ASME 1982 Orlando Conference, 1982.
[3-51 Ibanez, P., Keowen, R.S., and Renty, P.E., "Experimental Study of Dynamic Behavior of Piping Systems Under Maximum Load Conditions Testing." ANCO Engineers, Culver City, California, ASME 1982, Orlando Conference, 1982.
[3-6]
"Proposed Code Changes to Place Seismic Loading in the Fatigue Category," PVPC Technical Committee on Piping Systems. July 11, 1984.
[3-7]
Campbell, R.D., et. al., "Development of Dynamic Stress criteria for Design of Nuclear Piping Systems", Structural Mechanics Associates, Inc. Report No. 17401.01, Prepared for Pressure Vessel Research Committee, November 1982.
[3-8]
Smith, P.D., et. al., "LLL/DOR Seismic Conservatism Program:
Investigations of the Conservatism in Seismic Design of Nuclear Power Plants," Lawrence Livermore National Laboratory Report No.
UCRL-52716, 1980.
[3-9]
Maijoine, M.J., "Influence of Rate of Strain and Temperature on Yield Stresses of Mild Steel," Journal of Applied Mechanics, Volume II, ASME Trans., Volume 66, Pages A211-A218, 1944.
[3-10]
Levin H.A., Martore J.A., Reiter L., Jeng D., Heller L.W.,
"Reconnaissance Reports - Imperial Valley Earthquake, October 15, 1979," U. S. Nuclear Regulatory Commission, Washington D. C.,
Memorandum for Darrel G. Eisenhut (November 2, 1979).
[3-11]
NUREG/CR-1665 "Equipment Response at the El Centro Steam Plant during the October 15, 1979 Imperial Valley Earthquake," prepared by LLNL for the Office of Nuclear Reactor Regulation, October 1980.
R-2
Appendix A:
Comparison of LTS and SEP criteria and Methodologies for Piping Analysis Item LTS SEP Code Eqn. 9 (Level 0) Allowable 2.OS y
-2.4Sh for Class 2/3
-1.8S for Class 1 (or Sm using Class 1 rules)
Envelope Response Spectra Method o Mode Combination R.G. 1.92 or CQC R.G. 1.92 o Damping Code Case N411 R.G. 1.61 o Peak Shifting R.G. 122 or R.G. 122 Appendix N-1226.3 More accurate Methods May use.
Not specified.
Include MLRS, Time History and Nonlinear Analysis A-1
Appendix B:
List of Piping Materials and Allowable Stresses Max.
Operating Winter 1980 Code Temp.
2.4 Sh 2S (ksi) 2.4S /2S Material (OF)
(ksi) y h
y A312 TP304L 200 37.68 42.60
.88 A312 TP304 575 38.16 37.00 1.03 SA312 TP316 570 41.52 38.26 1.08 A106 B 545 36.00 54.44
.66 A53 B 340 36.00 61.20
.59 The apparent anomaly occurring in the table above, in which 2.0 S is actually less than 2.4 Sh for two materials, is easily explained y considering the basis of the allowable stress Sh.
As defined in Appendix III, Article 111-3000 of the ASME Code, Sh is defined as the lowest of:
Carbon Steel
- 1) 1/4 Su minimum (ambient temp.)
- 2) 1/4 Su (operating temp.)
- 3) 2/3 Sy minimum (ambient temp.)
- 4) 2/3 Sy (operating temp.)
Stainless Steel 1) 1/4 Su minimum (ambient temp.)
- 2) 1/4 Su (operating temp.)
- 3) 2/3 S minimum (ambient temp.)
- 4) 0.9, (operating temp.)
For SA 312 TP304 and SA 312 TP316, Sh is controlled by 1/4 Su at operating temperature and 0.9 S, at operating temperature, respectively. In these cases,.4 Sh is actually higher than 2.0 Sy as shown below:
For A312 TP304: Sh = 1/4 Su @ 5750F = 1/4 (63.5) = 15.88 ksi (Code uses 15.9 ksi) 2.4 Sh = 2.4 x 15.9 = 38.16 ksi Sy @ 5750F = 18.5 ksi 2 Sy = 2 x 18.5 = 37 ksi For SA312 TP316 Sy @ 570aF = 19.13 ksi Sh = 0.9 Sy @ 570'F = 0.9 x 19.13 =17.22 ksi (Code uses 17.3 ksi) 2.4 Sn = 2.4 x 17.3 = 41.52 ksi 2 Sy = 2 x 19.13 = 38.26 ksi B-1
100.
SR312 TP304L
- 80.
~60.
-j
-,2.0 S J
u' 20.
- 00.
200.
300.
400.
500.
600.
TEMPERRTURE (DECREE F)
IMPELL CORPORRTION MRTERIRL PROPERTIES RPPLICRBLE TO SONGS 1 LONG TERM SERVICE PROCRRM FIGURE B--2 B-2
100.
SA312 TP304 280.
uo)
U60.
- 40.
2.4 S cr h
z Lo E220.
- 0.
100.
200.
300.
400.
500.
600.
TEMPERATURE (DECREE F)
IMPELL CORPORATION MRTERIRL PROPERTIES RPPLICRBLE TO SONGS 1 LONG TERM SERVICE PROGRAM FIGURE B-3 B-3
100.
SR312 TP316
- 80.
1.
Lo
- 60.
L 2.0 S a
S J
z
- 20.
0100.
200.
300.
400.
500.
600.
TEMPERRTURE (DECREE F)
IMPELL CORPORRTION MRTERIRL PROPERTIES RPPLICRBLE TO SONGS 1 LONG TERM SERVICE PROGRRM FIGURE B--4 B-4
100.
SR106 B AND R53 B 2 80.
2.0 S I-Y uj 60.
Lu cm 40-2.4 S h
..J z
S20.
0.1 I
I 100.
200.
300.
400.
500.
600.
TEMPERATURE (DEGREE F)
IMPELL CORPORATION MATERIAL PROPERTIES APPLICABLE TO SONGS I LONG TERM SERVICE PROGRAM FIGURE B-1 B-5
Appendix C:
RTS Piping Frequency Review Following is a review of frequencies and accelerations for piping systems evaluated in the SONGS 1 RTS program which were stress-criteria-controlled.
The qualification of stress-criteria-controlled systems relied primarily upon linear elastic stress calculations (although nonlinear analysis methods may have been applied to isolated areas in the system).
TABLE C-1 Spectrum Spectrum Piping Piping Peak [2]
Peak [1 1st Mode [2]
1st Mode E11 Analysis Direction Acceleration (a) Frequency (Hz)
Acceleration (g) Frequency (Hz)
AF-02 Horizontal 1.80 3.12 1.40 1.68 Vertical 1.83 5.00 1.22 1.69 AF-05 Horizontal 2.70 6.30 Vertical 2.60 6.25 CV-11 Horizontal 3.45 6.80 Vertical 3.45 6.80 CV-12/
Horizontal 3.45 3.66 MW-01 Vertical 3.45 3.66 CV-13 Horizontal 3.45 11.50 Vertical 3.45 11.50 FW-04 Horizontal 3.00 4.05 Vertical 3.20 4.05 FW-124 N-S 3.50 6.78 E-W 3.50 6.78 Vertical 3.50 6.78 FW-125 N-S 3.50 6.78 E-W 3.50 6.78 Vertical 3.50 6.78 MS-03 N-S 4.20 6.80 E-W 4.00 6.80 Vertical 4.00 6.80 RC-103 N-S 2.27 6.80 E-W 2.33 6.80 Vertical 2.57 6.80 RC-107 N-S 2.64 5.40 E-W 2.75 5.40 Vertical 2.81 5.40 SI-150 Horizontal 3.50 5.22 Vertical 3.30 5.22 SI-155 Horizontal 3.50 6.72 Vertical 3.30 6.72 SI-158 N-S 3.30 5.40 E-W 3.30 5.40 Vertical 3.30 5.40 NOTES:
Ell Spectrum peak frequencies cited are lower bound values.
12]
Accelerations are cited Daly if the 1st mode frequency is on the flexible side (i.e., less than lower bound peak frequency) of the spectrum peak.
C-1
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