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Dec 1977

Volume 62, Issue S1, pp. S1-S102

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back to top Session FF. Shock and Vibration I: Simulation of Seismic Environment
Invited Papers
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Review of seismic design and testing (A)

H. C. Pusey

J. Acoust. Soc. Am. Volume 62, Issue S1, pp. S73-S73 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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It is well known that earthquakes can be devastating in terms of life and property. Along with the preservation of life, one of the more important concerns during these natural disasters is the survival of vital power and communications equipment. Over the past several years significant progress has been made in seismic design and analysis, and in techniques for simulation of seismic loads for purposes of equipment qualification. A review of the present state of the technology is presented with particular emphasis on seismic design approaches and test capabilities.
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Seismic qualification of equipment by generic testing (A)

G. D. Shipway

J. Acoust. Soc. Am. Volume 62, Issue S1, pp. S73-S73 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Generic testing has evolved as a very popular approach to seismic qualification of equipment for nuclear power plants. Generic testing is where equipment is tested to a high‐level seismic environment which is arbitrarily selected to encompass all, or nearly all, present and future requirements. This approch has presented uncertain areas of potential over conservatism, since beats superimposed on background random, difficult to handle OBE testing, and test levels which tax the capacity of testing machines. Other questions not yet answered by guides or standards are the appropriate accuracy for measuring and controlling the Test Response Spectrum and for measuring and controlling the zero‐period acceleration. The display of the TRS is not yet sufficiently standardized. How to perform seismic testing for line‐ (pipe) mounted equipment is an area begging a solution for which there is no current concensus. The solution will require in part a better definition of the pipe environment. The paper will present the details behind these areas of uncertainty and will offer suggested approaches and testing techniques towards standardized methods.
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Earthquake simulation and test procedure for communications equipment (A)

S. C. Liu and N. J. DeCapua

J. Acoust. Soc. Am. Volume 62, Issue S1, pp. S73-S73 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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A rational procedure for determining a regional earthquake test environment for communications facilities is described. The approach includes examination of a wide range of telephone building responses to arrive at an upper‐bound response spectra. An acceleration time history test environment in the form of a synthesized earthquake is generated to match the spectra. The regional test is then established by linearly scaling the time history to the peak acceleration shown on a national earthquake design regionalization map. Further scaling to account for motion amplification for in‐building location of equipment was achieved through examination of data gathered from the 1972 San Fernando earthquake. Communications equipment mounted on steel framework are tested for their earthquake vulnerability according to the specified laboratory test environment.
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Seismic and dynamic test capabilities at Combustion Engineering, Inc. (A)

K. H. Haslinger

J. Acoust. Soc. Am. Volume 62, Issue S1, pp. S73-S74 (1977); (2 pages)

Online Publication Date: 11 Aug 2005

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A description of CE's Seismic Test Facility and a discussion of its use for environmental qualification of mechanical and electrical equipment will be presented. The presentation will focus on the Biaxial Seismic Simulation Fixture on the Digital Vibration Control System with Modal Analysis Capabilities. The various electrodynamic shakers and their use for steam generator tube vibration tests, as well as for on‐site testing of large cabinet structures (resonance survey and identification of mode shapes and modal damping parameters) also shall be covered. Photographs will be shown which depict the various shaker installations with typical test setups. CE's approach to seismically qualifying some complex structures through combined analysis and test techniques will be demonstrated through work performed on Nuclear fuel assemblies and control element drive mechanisms. A brief outline of CE's analytical capabilities shall be given.
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Two‐phase model to predict the inelastic, seismic response of a steel frame (A)

Hugh D. McNiven and Vernon C. Matzen

J. Acoust. Soc. Am. Volume 62, Issue S1, pp. S74-S74 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Previous papers reported on the use of a nonlinear differential equation (containing a Ramberg‐Osgood term) to represent the inelastic, seismic behavior of a single‐story steel frame. The structure was tested on the shaking table at the Earthquake Engineering Research Center at the University of California, Berkeley. The correlation between the predicted and measured acceleration time histories was exceptionally good. However, the computed displacement time histories did not predict the permanent offset experienced by the structure. The reason for this shortcoming is that the hysteretic behavior of virgin steel is different in the first inelastic excursion than it is in subsequent excursions. The Ramberg‐Osgood model can represent only the subsequent hysteretic behavior. To alleviate this deficiency, the present paper presents a two‐phase model. One set of parameters is established for the initial phase of the response, in which hysteretic behavior is approximately elastic, perfectly plastic; and another set is established for the second phase, in which the hysteretic behavior has a more rounded transformation from elastic to plastic deformation. The importance of this work lies not so much in its application to steel, as in its potential for application to degrading materials like reinforced concrete and masonry.
Contributed Papers
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Algorithm development for signal‐selective seismic field recorders (A)

Wm. Mansfield Adams

J. Acoust. Soc. Am. Volume 62, Issue S1, pp. S74-S74 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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A seismic field recorder has been developed based on the MC6800 microprocessor [W.M. Adams, Geophys. Prospect. (to be published, 1977)]. This allows the real‐time implementation of algorithms for selecting the signals from the microseismic background and hence for recording primarily signals. The advantages are the greatly reduced amount of recording media that must be processed at the central data‐processing depot and the reduction in the amount of data processing that must be done later; the current disadvantages are the battery requirements, the complexity of the equipment, and the lack of effective algorithms. The first two defects will be solved by component evolution; here we discuss the last factor. The present system is not self‐adapting. Instead, continuously recorded data are processed by heuristic procedures to find an improved method of selecting the signals from the background. Because of spurious impulsive noise, an energy‐content discriminator followed by a zero‐crossing (frequency) discriminator is found to be superior to the usual threshold trigger, such as used to turn on the strong motion accelerographs for earthquake engineering research. The algorithm used by the Seismic Research Observatory (SRO) of the USGS is compared with the energy‐content + zero‐crossing processing. [Work supported by NSF.]
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