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. F' RANK NEUMANN ~ g3 y *b SEssMOLOSiev. GEcLosY DEPARTMENT UNIVERSITY OF WASHIN 5?DN SEATTLE S.WASHIN GTON June 24,1963. *
- Dr. Robert H. Bryan, Chief, Research and Power Reactor Safety Branch, Division of Licensing and Regulation, U. S. Atomic Energy Commission, Washington 25, D. C.
Dear Dr. Bryan:
Over the week end I have reviewed the material for-warded with your letter of June 20 and in other ways have endeavored to reconcile my views with PG&E's engineering plans for the proposed
. Bodega Head power plant. There are still some unanswereiquestions
._ which I shall touch on briefly in ocumenting on the rglios to the recent inquiries. Reference is made to the questions in Mr. Lowen-stein's letter of May 24, 1963 and the PG&E replies in Aamendment No. 3 (Docket No. 50-205) .
The answer io question 1 is straightforward enough; I sm just a little skeptica.'. about the optimism expressed in view of the fact that Housner in his paper " Behavior of Structures During Earthquakes" (Journ. Eng. Mech. Div., ASCE, Oct.1959) and-Blume, Newmark and Corn-ing in their book "' Design'of Multistory Reinforced Conorate ~ Buildings for Earthquake Motions" both give the impression that one should never ;
expect even a well designed structure to escape damage entirely in an I earthquake of abnormal intensity. Housner says (p.128):"It is more !
, - reasonable to take,the point of view that -- in the more rare event' ,
of a very strong ground motion, damage would be tolerated so'long as it was not a hasard to life and limb. This is the usual point of view of engineers". Blume, Newmark and Corning state (p.vi) " The -
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objective is to proportion a structure in such a way that -- the structure should not collapse even when subjected to the motions of . i an earthquake of abnormal intensity". This- evidently is what the Uniform Building Code contemplates and this is the code that will be '
used in designing critical structures at Bodogs. Head.
In question 2 Mr. Lowenstein asked "What ground motions are to be used for dynsaio design?". Housner answered by stating "The design of critical structures will be based on the design velocity spectrum ;
shown on the attached sheet". This is not an answer to the question. ;
It is noted thsit for the respective' dampings of 15%, 7.5% and 2.5%
the spectra 1Tr reformational motions would be only about 1.5, 2.0 and 3.5 times greater than the El Centro . ground motions. If the El i Centro ground motions were doubled as suggested in my recent report . -
to you the reformational motions would be only".75,1.0 and 1.6 '
times the ground motions. . What concerns me is that Coast and Geodetic seismographs placed on the top floors of building,s show approximately 5 to 10 times as much motion on top floors as in basements. The higher:
1 slues no doubt indicate resonance' or partia oe. Realizing
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thatthese top floor motions are not reformational motions (Building '
notions relative to the round motion) and that at the building's' t centers the motions ma uly about half the top floor motions the
'l resulting ratios are never-the-less so much greater than indiented in
- I the. proposed velocity spectrum sad the El Centro ground motion as to ,
- I. be a cause for some second thoughts. Considerable data on top floor '-
i building motions during earthquakes are available but ' engineers seem
! to prefer using theoretical building motions (velocity spoetra) in.
J their estimates of structural deformations. (I believe a test.or-r- two was made with controlled explosions with this in mind).
If you do not have the B1tane,' Newmark, Corning book you should l
-i by all means get it; the preface is especially interesting. It is (
( difficult to reconcile the unquestionable sureness that permeates j j the PG&E proposals and ammendments with the sometimes almost epolo-gotic attitude found in professional papers on the same subject where ,
researchersadmittheexploratorynatureoftheentirejoissiodesign problem and the dearth of adequate knowledge in so many important .,
r :- phases of it.
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, In answerg No. 3 Housner states:"a further analysis will be made j to insure that ground motion five times as intense as the design spoo-d i- - trian will be required to produce incipient failure of structure". Ii' )
L the design velocity spectra are multiplied by 5 and drawn on a 4-way
, log chart it will be_seen that the tround motions will range from
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2.5 to 4.6 g. Is this what is meant? If not, just what is the ground motion that is related to the ' design spoetra -- same as question No. 2.
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With reference to the design lateral acceleration at'the roof level-of the reactor structure being nine times larger than is specified by
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the Uniform Building Code does this refer to a design acceleration in
!n Zone 1 (minor damage) or Zone.3 (major damage)? In Zone 3 the code a calls for increasing lateral force factors four times over those used r in Zone 1. This would sesmingly represent a doubling of the lateral
- force factor over that called for anywhere in Zone 3 earthquake areas "
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,l - -- to take care of maximum forces in the epioentral area. Just what i, intensity does Zone 3 signity? -
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) The proposed damping factors are less than had been anticipated.
i! They would on11 for quite large ratios between expectable building l: -
(spectral) motions and ground motions; not the minimum so often found
.f in the computations of oscillator spectra.
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The answer to question No. 4 should be left to geologists exclus-s
]. ively.
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- Sincerely yo e, !
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,* N" Frank Neumann, Seismologist.
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a OFFICE OF THE CHAIRMAN
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