Transient Motion Measurements for Structural Response Analysis

Citation

Rubin, Sheldon (1956) Transient Motion Measurements for Structural Response Analysis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ND1B-3V27. https://resolver.caltech.edu/CaltechETD:etd-06252004-104122

Abstract

The theory of the design of instruments suitable for the measurement of the acceleration-time history of a transient motion is considered. It is assumed that the primary purpose of the acceleration-time record is the calculation of structural response. As a criterion of instrument behavior, it is proposed that the correct reproduction of the response spectrum of the transient motion be adopted. The application of this response spectrum criterion to some selected acceleration pulses indicates that the optimum instrument parameters for a transient measurement are essentially the same as for the measurement of periodic motions. A general theory for the multiple degree of freedom seismic accelerometer characteristics is established. The particular case of a two degree of freedom accelerometer is studied and it is shown that the sensitivity to acceleration can be increased to about five times that of a single degree of freedom instrument having the same useful frequency range. An instrument which can be used to obtain structural response information directly, without the necessity of an acceleration-time recording is studied. This instrument, the reed gage, gives directly information concerning the transient response of a single degree of freedom system or of individual modes of a complex structure. The total response of a complex structure can be determined from reed gage information by the superposition of the maximum responses in the individual modes. An analysis is made of the errors in total response inherent in this superposition process. It is found that in many practical problems the distribution of mode frequencies and the form of the excitation is such that the total error due to superposition is not a significant factor in the problem.

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