摘要:

AbstractCones can be used to model soil in a unified strength‐of‐materials approach. For the vertical and rocking motions involving predominantly compressional‐extensional deformation, the corresponding dilatational wave velocity tends to infinity for Poisson's ratio approaching 1/2. Based on the rigorous solution for the dynamic stiffness of a rigid disk for all frequencies, whereby the partition of the power among P‐, S‐ and Rayleigh waves is also discussed, two special features are necessary for the vertical and rocking motions for nearly incompressible soil with Poisson's ratio between 1/3 and 1/2: (1) The appropriate wave velocity is selected as twice the shear wave velocity and not as the dilatational wave velocity; (2) A trapped mass which increases linearly with Poisson's ratio is introduced. The trapped mass can be assigned to the base mat, allowing the cone model to be constructed in the same way for all Poisson's ratios. The realization of cone models for surface foundations on a homogeneous half‐space and on a layer on a flexible half‐space and for embedded and pile foundations

ISSN:0098-8847    

DOI:10.1002/eqe.4290220802

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractEl Infiernillo, a 145 m high rockfill dam in Mexico built in a narrow V‐shaped canyon, was subjected to eight major earthquakes since its construction. In this study, the dynamic dam response is analysed using (i) the recorded November 15, 1975 bedrock‐crest acceleration histories and (ii) the results of a 1970 full‐scale test conducted by UNAM, in which eight upstream–downstream and longitudinal resonant frequencies and configurations were observed and documented. These observed and seismically induced dynamic responses are compared herein to predictions of two different numerical models of El Infiernillo dam; a newly developed simplified three‐dimensional (3D) model, and a 3D finite element model. The dynamic dam response characteristics are assessed, and performance of the employed numerical models is evaluated. It is found that (i) higher modes of vibration had participated significantly in the recorded seismic response and (ii) upstream–downstream response is well represented by the two numerical models employed. Using the simplified model, the September 19, 1985 earthquake non‐linear response is computed and shown to compare satisfactorily with its recorded counterpart in the upstream‐downstream and vertical directions. The largest computed dynamic accelerations, stresses and strains are found to occur within the upper third

ISSN:0098-8847    

DOI:10.1002/eqe.4290220803

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe paper presents results of a parametric study of vertical oscillations of a flexible circular plate on the surface of an elastic half‐space and an elastic layered system. The solution of the problem is based on the ‘ring method’. Vertical oscillations have been analysed to determine the displacement and soil reaction distributions at the soil‐plate interface and the impedance functions. Parameters of the study include material and geometrical properties of a soil system and a plate and the load distribution on the plate. The results indicate significantly different behaviour of a flexible plate from that of a rigid one. Based on the observed behaviour, a classification of plates has been su

ISSN:0098-8847    

DOI:10.1002/eqe.4290220804

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAttenuations of the vertical and horizontal response spectra of the 17 October 1989 Loma Prieta, California, earthquake are developed through analyses of the ground motion at 53 sites within a 100 km radius of the source. The analyses are performed on the spectral ordinates for 16 incremental periods ranging from 0.05 to 2.0 sec. The response spectra are modelled empirically for two different site conditions characterized by rock and stiff‐soil geologies. Data analysis is performed by the application of a non‐linear multivariate regression procedure allowing for distance and site factor as independent variables. Variation of the vertical‐to‐horizontal (V/H) spectral ratios with wave frequency and distance shows the same behaviour as observed previously in the widely separated geographic regions of northeastern Taiwan and east‐central Iran. The predicted ratios at sites underlain by stiff soil are generally higher than the commonly used value of 2/3 at high frequencies (>5 Hz) in the near‐source region (R<30 km), but reduce to 1/2 or less at longer periods and farther distances. This behaviour is also observed at rock sites; however, it is somewhat less pronounced.With a faster attenuation of spectral ordinates at higher frequencies, the shape of the response spectrum is found to change with distance. As expected, the spectral attenuation with distance is generally higher for the vertical spectrum than for the horizontal spectrum. The difference is particularly significant at the higher‐frequency end of spectrum.Site amplification factors for stiff soil with respect to rock geology varies between 1.17 and 1.72 for horizontal spectrum and 1.01 and 1.81 for vertical spectrum. Spectral amplifications at four sites underlain by soft soil and artificial fill, are also evaluated. This is done by a comparison of the observed spectra with those predicted for rock geology at corresponding distances. As expected, the resulting amplification factors at soft‐soil sites show significant increase relative to those at sites un

ISSN:0098-8847    

DOI:10.1002/eqe.4290220805

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe paper is concerned with the earthquake‐induced displacements on pre‐existing shear surfaces in cohesive soils. Results from ring shear tests have shown that during fast shearing the strength of such surfaces depends on displacement and rate of shearing. The test results have been used in a numerical analysis to assess the displacement of a rigid block sliding on a plane surface. The results from the analysis show that the earthquake‐induced displacements on pre‐existing shear surfaces are influenced significantly by the soil behaviour under earthquake loading conditions. The results are consistent with the field performance of pre‐existing slides in cohesive soils during ea

ISSN:0098-8847    

DOI:10.1002/eqe.4290220806

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA spectral method for random vibration analysis of a structural system with non‐proportional damping is presented using classical (undamped) mode superposition technique. The method obtains the frequency response function of the system by solving the dynamic equilibrium equations in generalized co‐ordinates through an iterative process. The iterative solution is written in closed form and the proof for convergence of the iterative process is given. Numerical examples show the convergence characteristics of the process and an excellent accuracy of the obtained results. The method turns out to be computationally more efficient than the conventional methods of spectral analysis using damped mode shapes and frequenc

ISSN:0098-8847    

DOI:10.1002/eqe.4290220807

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290220808

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290220809

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290220801

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY