摘要:

AbstractTo represent a cylindrical rigid foundation vibrating in horizontal, vertical, rocking or torsional motions embedded in a soil layer resting on rigid rock, a lumped‐parameter model is described. The coupling between the horizontal and rocking degrees of freedom is considered. For each degree of freedom eight frequency‐independent real coefficients determine the springs, dashpots and the mass of the lumped‐parameter model with two internal degrees of freedom. These coefficients are specified for various ratios of the radius of the foundation to the depth of the layer and lateral contact ratios. To derive the mechanical properties of the lumped‐parameter model a systematic procedure of curvefitting of the dynamic‐stiffness coefficient up to, in general, twice the fundamental frequency of the layer is applied, capturing the fact that below the (horizontal) fundamental frequency (cutoff frequency) no radiation of energy occurs. The lumped‐parameter model can be used to represent the soil in a standard finite‐element program for structural dynamics working in the time domain, whereby the structure can exhibit non‐linear behaviour. Stability of the unbounded soil‐layer model and of the total system is guaranteed. A hammer foundation with partial uplift of the anvil is analysed

ISSN:0098-8847    

DOI:10.1002/eqe.4290211201

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper studies the stochastic responses of secondary systems in base‐isolated shear beam structures. A number of base isolation systems such as the laminated rubber bearing (LRB), the resilient‐friction base isolator (R‐FBI) with or without sliding upper plate, and the EDF system are considered. The stochastic models for the El Centro 1940 and the Mexico City 1985 earthquakes which preserve the non‐stationary evolutions of amplitude and frequency content of ground accelerations are used as earthquake excitations. The technique of equivalent linearization is utilized and the mean‐square response statistics of secondary systems and primary structure are evaluated. The accuracy of the linearization scheme is verified by comparison with the Monte Carlo simulation results. Statistically estimated peak responses of the secondary system are evaluated and the results are compared with the response spectra for actual earthquake accelerograms. It is shown that the use of base isolation systems, generally, provides considerable protection for structural contents. In particular, the LRB system is remarkably effective in reducing responses of secondary systems. Results for the Mexico City earthquake show that the base‐isolated structures are sensitive to long period ground

ISSN:0098-8847    

DOI:10.1002/eqe.4290211202

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper considers a main structure supporting a large number of substructures. The substructures have closely spaced natural frequencies, and the combined main structure/multiple substructures system is subjected to harmonic or wide‐band forces. The goal is to characterize the effects of the substructures on the response of the main structure.A special, fundamental case is studied in detail, where the substructures are oscillators with equal stiffnesses and equally spaced natural frequencies. The exact response expressions for the combined system are in terms of a complicated rational polynomial. However, by taking the limit where the number of substructures becomes large, the response expressions reduce to simple, physically meaningful results. It is found that the multiple substrutures are equivalent to a single viscous damping which is added to the damping of the main structure. An example illustrates how the results can be applied to passive vibration control of large structure

ISSN:0098-8847    

DOI:10.1002/eqe.4290211203

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA time domain boundary element in a cylindrical coordinate system is developed for the analysis of wave propagation in a half space. The integral formulation is based on Graffi's dynamic reciprocal theorem and Stokes' fundamental solutions. The field quantities (displacements and tractions) are expressed as products of Fourier series in the tangential direction and linear polynomials in the other spatial directions. Gaussian integration is used to integrate the non‐singular parts of the integral equations, whereas the integration of the singular components, which are either of order 1/ror 1/r2, is handled by special numerical schemes. In the time marching aspect, the field quantities are assumed to vary linearly in the temporal direction as well.Examples for wave propagation due to various forms of surface excitations are reported to demonstrate the accuracy of the metho

ISSN:0098-8847    

DOI:10.1002/eqe.4290211204

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA new analytical method is presented to study the problem of scattering of plane SH waves by a semi‐cylindrical hill in an otherwise homogeneous, isotropic and elastic two‐dimensional half‐space, using the series of wave functions and a new expansion technique. The results obtained show that (1) the hill has quite considerable effects on ground motions for both the points on the hill and its environs, (2) these effects depend mainly on the frequency, the angle of wave incidence and the ratio of radius of hill to one‐half the wave length of incident waves, and (3) prominent and depression topographies having equal form and radius for the same incident waves would cause quite different mechanisms of wave propagation in both response performance and magnitude. The results, doubtless, would be useful for further deepening knowledge of the effects of prominent topography on seismic ground motion and for testing the accuracy of various approximate methods so far av

ISSN:0098-8847    

DOI:10.1002/eqe.4290211205

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290211206

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY