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- b F' RANK NEUMANN ~
g3 y 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 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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I 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
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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-two was made with controlled explosions with this in mind).
r-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
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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 answer No. 3 Housner states:"a further analysis will be made j
g 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'
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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.
i With reference to the design lateral acceleration at'the roof level-s 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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-- to take care of maximum forces in the epioentral area. Just what l
i, intensity does Zone 3 signity?
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The proposed damping factors are less than had been anticipated.
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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-
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ively.
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I Sincerely yo e,
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Frank Neumann, Seismologist.
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OFFICE OF THE CHAIRMAN
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For preparation of reply for Chairman's signature (Refer to Manual Chapter 0240)
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-1 For distribution to other Commissioners
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