摘要:

AbstractThe proper choice of the acceptable seismic risk requires an accurate cost‐benefit analysis. As is well known these analyses present considerable difficulties if one wishes to face the problem in a general way from the technical point of view. Besides, there are no generally accepted criteria for formulating a quantitative evaluation of the intangibles, among which the most important is the risk to human life. However, it appears indispensable that research should be started in the field which leads to some numerical resultsIn this paper a simplified analytical model is proposed and the problem of intangibles is discussed. The basic idea is that the comparison with other risks is the most realistic instrument for the choice of an acceptable level of the specific considered risk. The conclusion reached is that a fundamental index for comparison and decision is the incremental cost of investment necessary to save, on average, one human life a year. An evaluation of such an index, valid as a first approximation, is given for this simplified mode

ISSN:0098-8847    

DOI:10.1002/eqe.4290020102

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractAn approximate analytical solution is presented for torsional vibrations of footings partially embedded into a semi‐infinite medium or a stratum. Simple formulas derived for pure torsional motion make it possible to apply a correction for the effect of embedment to the known solutions of surface footings. The solution completes an approach to the analysis of all modes of footing vibrations, including the coupled modes. The approach to coupled modes is illustrated by the solution of coupled response involving horizontal translation, rocking and torsion. Formulas are presented for stiffness and damping coefficients that can be used in the analysis of embedded footings or structures supported by such footingsField experiments were conducted with concrete footings featuring circular, square and rectangular bases and variable embedment depths. The experimental results were compared with theoretical predictions of pure torsional vibration

ISSN:0098-8847    

DOI:10.1002/eqe.4290020103

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe effect of stiffness degradation in reinforced concrete structural members on the inelastic response of multistorey buildings to earthquakes is investigated. In particular, the following question is examined. How do the ductility requirements for multistorey systems with degrading stiffness behaviour compare with those for structures with ordinary bilinear hysteretic property? Inelastic dynamic responses of two idealized multistorey buildings, one having a long and the other a relatively short fundamental period, to an ensemble of twenty simulated earthquakes representative of moderately intense ground motions in California at moderate epicentral distances on firm ground, are analysed for ordinary bilinear hysteretic behaviour and for bilinear hysteretic behaviour with stiffness degradation property. The conclusions deduced from the results of this investigation include the following(1) It is, in general, not possible to predict the maximum response of a degrading stiffness system from results for the corresponding ordinary bilinear system(2) The differences in ductility requirements due to stiffness degradation are generally smaller than those associated with probabilistic variability from one ground motion to another(3) Stiffness degradation has little influence on the ductility requirements for flexible buildings, but it leads to increased ductility requirements for stiff buildings.

ISSN:0098-8847    

DOI:10.1002/eqe.4290020104

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractIn the dynamic response analysis of extremely complex structural systems in which the damping characteristics of each element are independent, the damping matrix is not always diagonalized by the use of undamped free vibration mode shapes. In the present paper, a mode‐superposition method by the use of damped free vibration mode shapes is developed for such structural systems. It is also shown that the Fast Fourier Transform (FFT) procedures, that are available for the dynamic response analysis of linear structural systems, are used effectively in this mode‐superposition method with good accur

ISSN:0098-8847    

DOI:10.1002/eqe.4290020105

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractPrediction of response spectra for earthquake engineering purposes is considered from a new point of view based on the dislocation theory of earthquakes. It is shown that the traditional scaling of response spectra by the predicted peak acceleration should be limited to the high‐frequency end of the spectrum, and that the peak acceleration in the near field is not strongly correlated with earthquake magnitude. The amplitude of the long‐period end of response spectrum at source to station distances greater than about 10 source dimensions should be scaled with seismic moment, while for distances less than about one source dimension this amplitude should be proportional to the permanent ground displacement. To reconcile the existing extensive data on seismicity of active regions based on magnitude scale, it is shown that magnitude can be used to determine approximately the seismic mom

ISSN:0098-8847    

DOI:10.1002/eqe.4290020106

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractWhen measured earthquake accelerations are used as a basis for structural design, then acceleration errors of a few per cent are usually acceptable. However a number of tasks in structural design, and in earthquake engineering research, require measured accelerations with errors limited to a few parts per thousand. Such tasks include those which call for the calculation of angular accelerations, the comparison of acceleration spectra or the calculation of relative displacementAccurate accelerations may be obtained from existing accelerographs by applying the results of an accurate static calibration to an accelerogram, and then applying corrections for the effects of accelerometer resonance. This paper concentrates attention on the correction of static errors, including sensing direction errors and cross‐axis interaction errors. For completeness there is a brief discussion of dynamic errors, which depend on accelerometer periods and dampings. It is concluded that earthquake accelerations may be obtained with errors of not much more than 0·001 g, the resolution of a typical accelerograph, at least for periods greater than 0·2 sec. When the accelerations have shorter periods, larger errors may arise due to the limited accuracy of the corrections for dynamic errorsThe static calibration of accelerographs, and the corresponding record correction procedures, are illustrated by application to the M.O.2 accelerogr

ISSN:0098-8847    

DOI:10.1002/eqe.4290020107

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractSimple approximate solutions are presented for the steady‐state response of a massless, rigid disk, which is supported at the surface of a linear viscoelastic halfspace and is excited by a harmonically varying horizontal or vertical force, or by a harmonically varying moment about an axis in the plane of the disk. The halfspace is idealized either as a standard Voigt solid or as a constant hysteretic solid. The solution for the massless disk is then applied to the analysis of foundations with mass, and for each mode of excitation, comprehensive numerical data are presented to illustrate the effects of viscoelastic action on the response of both the massless disk and of foundations with massIt is shown that the principal effects of material damping are to increase the damping capacity of the foundation and to reduce its ‘natural’ frequency. In the mathematically equivalent representation of the elastically supported massless disk as a spring‐dashpot combinationwithoutmass, it is shown that the effective stiffness of the spring may become negative over significant ranges of the exciting frequency, and that it is preferable to model the disk‐halfspace system as an oscillatorwithmass, taking its spring constant equal to the static stiffness of the origin

ISSN:0098-8847    

DOI:10.1002/eqe.4290020108

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290020109

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290020110

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290020101

出版商:John Wiley&Sons, Ltd    

年代:1973

数据来源: WILEY