摘要:

AbstractAn important aspect of earthquake loads exerted on extended structures, or structures founded on several foundations, is the spatial variability of the seismic motion. Hence, a rigorous earthquake resistant design of lifeline structures should account for the spatial character of the seismic input, at least in an approximate way.A procedure is proposed which enables addressing the problem of multiply supported structures, subjected to imperfectly correlated seismic excitations, by means of an extension to the response spectrum method. A modified response spectrum model is developed for the design of extended facilities subjected to single and multicomponent ground motion. The modification procedure is based on adjusting each spectral value of the given design response spectrum by means of a correction factor, which depends on the structural properties and on the characteristics of the wave propagation phenomenon. Finally, the theoretical model is validated through digital simulation of seismic ground motion, whereby model predictions are found to be in good agreement with exact results.

ISSN:0098-8847    

DOI:10.1002/eqe.4290210601

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA control design for absolute motion reduction of base‐isolated structures subjected to earthquake excitation is presented herein. The control objective is to provide a vibration‐free environment for sensitive equipment protection. Predictive control theory is used for the control design. This theory allows the designer to handle time delays generated by the dynamics of actuators. The study reported herein demonstrates, by numerical simulation, the efficacy of this controller in reducing acceleration response in the superstructure in the presence of delays. Stability analysis, frequency response and response to ground motion excitation are developed to assess the characteristics of the control

ISSN:0098-8847    

DOI:10.1002/eqe.4290210602

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAt many sites on soft ground, spectral ratios (ratios of smoothed Fourier amplitude spectral ordinates at the site to those at a station on firm ground) for distant earthquakes are little sensitive to focal mechanism and coordinates and to magnitude. Spectral ratios furnish directly expected Fourier amplitude spectral ordinates at the site of interest. The corresponding response spectra can be estimated through the use of random vibration theory. This step is obviated by resorting directly to ratios of response spectral ordinates. Through comparisons for several sites on the Valley of Mexico we find that these ratios are as stable as those of Fourier amplitude spectral ordinates.

ISSN:0098-8847    

DOI:10.1002/eqe.4290210603

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe strong ground motion produced by the 17 October, 1989 Loma Prieta earthquake in northern California was recorded at over 100 stations. Accelerograms were generated at sites with significantly different geology, including land fill and soft sedimentary soil sites. In this study, the attenuation characteristics of the peak vertical and horizontal ground accelerations are studied for freefield recording conditions within 100 km of the source by the application of a non‐linear multi‐regression procedure. Two sets of attenuation models for weighted and unweighted observations are compared with those reported by other investigators for this earthquake and for regional and worldwide data. Thepeak ground acceleration(PGA) observations for this earthquake exceed previous predictions of standard attenuation models, particularly beyond 30 km (approximately 60 percent at 50 km). Higher attenuation of the vertical component compared to the horizontal is confirmed.The regression considers site geology as an independent parameter. Soil sites display as much as 23 per cent amplification relative to rock sites for horizontal PGA and as much as 40 per cent for vertical PGA. Amplification of the ground motion at sites characterized by soft soil geology is examined by comparing the recorded PGA with the corresponding prediction at sites underlain by stiff soil. Eight of ten of the soft soil sites display significant amplification relative to stiff soil sites (as much as 300 per cent for horizontal and 200 per cent for vertical components). Particular attention is paid to the so‐called anomalous observations at distances beyond 50 km. The anomalous observations between 50 and 80 km may be attributed to various factors such as geology, basic geometry, azimuthal dependence, source mechanism and normal scatter of observa

ISSN:0098-8847    

DOI:10.1002/eqe.4290210604

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe problem of defining objective isoseismal maps is as yet unresolved. The aim of the work, here presented, is to show how the studies of different authors and eras can produce contrasting, even contradictory, interpretations of the macroseismic data set for the same earthquake.At this point in time, the principal macroseismic end (i.e. that which furnishes seismology, seismotectonics and studies of seismic risks with descriptions of the effects of earthquakes, as far as possible exempt from interpretation) is in danger of failing.Throughout this work, we have sought to bring to light how certain anomalies of macroseismic maps principally reside in the diversity of data interpretation, and how it is possible to put in evidence these by applying appropriate statistical analysis to the macroseismic fields.The Sicilian earthquake of 11 January 1683 (I0= XI) was taken as an example, as a sufficient quantity of information was available; a filter procedure was then applied to the macroseismic data. Finally we also show that such procedures are very useful in the treatment of border earthquakes, in an attempt to homogenize macroseismic fields from different countries.

ISSN:0098-8847    

DOI:10.1002/eqe.4290210605

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe relative advantages of several control strategies to reduce the seismic response of multi‐storey structures are studied. The strategies involve the separate or combined use of passive base isolation mechanisms and active control forces. The base isolation mechanism is modelled as an equivalent linear soft storey with high damping. The active control forces are selected so that an absorbing boundary is obtained at the top of the structure and non‐reflecting or reflecting boundaries are obtained at the base of the building. It is found that the best results are obtained when a passive base isolation system is combined with an active absorbing boundary placed at the top of the building. However, the incremental gains resulting from adding a base isolation system to a structure already controlled by a roof‐top active absorbing boundary are significant only for relatively soft base isolation systems. Also, the incremental gains appear to decrease as the number of storeys of the structure incr

ISSN:0098-8847    

DOI:10.1002/eqe.4290210606

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA time‐integration procedure for dynamic analysis of non‐classically damped systems, in which high‐frequency modes play a significant role, is suggested. This procedure is an extension of Clough and Mojtahedi's1method. Clough and Mojtahedi suggested integration of the transformed coupled equations of motion where the transformation is done using a truncated set of undamped mode‐shapes. The proposed extension consists in adding the response of all the higher modes through a quasistatic analysis. Approximations involved in using such a procedure are examined. Numerical results presented indicate that the proposed extension leads to a significant improvement over Clough and Mojtahedi's

ISSN:0098-8847    

DOI:10.1002/eqe.4290210607

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210610

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210611

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210612

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY