摘要:

AbstractThe theoretical implications of an isolation mechanism that utilizes progressively increasing frictional resistance is investigated. This type of frictional resistance can be provided by the tightening together of a set of friction plates by compressive forces that increase with relative separations of the building and the foundation. The mathematical model of the device is developed and its numerical solutions are obtained. It is shown that in comparison with dry friction alone significant reductions in acceleration transmissibility and relative displacement transmissibility can be obtained.

ISSN:0098-8847    

DOI:10.1002/eqe.4290150702

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAn extension of the boundary element method to heterogeneous domains composed of horizontal layers is here proposed. It includes a numerical computation of the corresponding Green's functions, thanks to an inverse Hankel transform of the closed form solutions obtained in the spectral domain with suitable variables derived from displacements and stress vectors to obtain the decoupling between P–SV and SH waves. Transmission and reflection operators are introduced to avoid the problem of overflowing exponentials met with in Thomson–Haskell matrices.Applications are given in the soil–structure interaction field to compute the impedances of surface and embedded circular foundations resting on a viscoelastic half

ISSN:0098-8847    

DOI:10.1002/eqe.4290150703

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe problem of the transmitting boundary used in the dynamic finite element analysis of layered axisymmetric soil models with non‐axisymmetric displacements is considered. Each layer is modelled as a homogeneous, viscoelastic cross anisotropic medium with a vertical axis of material symmetr

ISSN:0098-8847    

DOI:10.1002/eqe.4290150704

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractStarting from two‐dimensional wave equations and making use of Galerkin weighted residual approximations, discretized formulations for wave problems of a visco‐elastic foundation have been derived. With considerations of geometrical and mechanical characteristics of a semi‐infinite domain, a frequency‐dependent compatible infinite element is also presented. Finally, by coupling the infinite elements with ordinary finite elements the system is used for simulation of propagating waves in a semi‐infinite foundation. This model is not only suitable for simulations of complicated variations of geometrical conditions, but also for describing the unbounded behaviour of arbitrary multiple layers. Examples given indicate the model has excellent computational accuracy and feasibility for analysing the effects on foundation response due to the existence of faults or any other so

ISSN:0098-8847    

DOI:10.1002/eqe.4290150705

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractIn this study it has been shown that, in the case of linear theory, the combined internal forces corresponding to each seismic direction lie on an ellipsoid having internal forces chosen as the set of axes. A method is proposed to obtain the most unfavourable results easily, in the neighbourhood of the several unfavourable points without actually determining the ellipsoid. The design can be carried out using linear, as well as non‐linear, theory. Two examples are given to illustrate the application of the proposed metho

ISSN:0098-8847    

DOI:10.1002/eqe.4290150706

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe ramifications of a particular type of causality constraint, namely so‐called shadow‐zones, are explored in the context of time‐dependent boundary element methods. In particular, wave propagation problems in 2‐D elastic soil media with a non‐convex shape are

ISSN:0098-8847    

DOI:10.1002/eqe.4290150707

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA method is presented to obtain the exact complex‐valued eigenproperties of a classically damped structure and equipment system. The non‐classically damped character of the combined system as well as the effect of dynamic interaction between primary structure and equipment are properly included in the calculation of these eigenproperties. It is necessary only to know the classical modal properties of the structure and, of course, the equipment characteristics. The eigenvalues are obtained as the solution of a non‐linear equation which can be easily solved by the Newton–Raphson algorithm. Once the eigenvalues are known, the corresponding eigenvectors are obtained from simple closed‐form expressions. The method can be used equally effectively with light as well as heavy equipment. Numerical results demonstrating the effectiveness of the method are presented. A procedure which utilizes the complex‐valued eigenproperties is developed for calculating the floor response spectra directly from the ground spectra. Numerical results of floor response spectra obtained from this procedure are presented. The floor spectra calculated by this approach include the structure–equipment inter

ISSN:0098-8847    

DOI:10.1002/eqe.4290150708

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of the space–time variation of earthquake ground motion on the translational response of structures supported on large rigid mat foundations is considered. A stochastic space–time ground motion model, based on the analysis of recordings from the SMART‐1 seismograph array in Lotung, Taiwan, is used. Random vibration theory is utilized to obtain an expression for the reduction in the maximum structural response, for a specified probability level and strong motion duration. Numerical computations are performed to examine the sensitivity of the reduction in structural response to various ground motion and structural parameters. The results indicate that spatial correlation and travelling wave effects give rise to significant reductions in structural responses when the seismic waves have low apparent propagation velocities. Utilization of this result in the design of structures on large foundations should yield substantial cost sa

ISSN:0098-8847    

DOI:10.1002/eqe.4290150709

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractMost of the step‐by‐step time integration algorithms for structural dynamics require an initial acceleration vector to be specified, in addition to displacement and velocity vectors. A consistent initial acceleration vector may be calculated by solving the equations of motion at the initial time, while a truncated initial acceleration vector is obtained by setting the acceleration values to zero. Although the truncated starting procedure decreases computational effort, it is shown to affect accuracy adversely. For the structural dynamics algorithms considered herein, the rate at which the numerical solution converges to the exact solution isO(Δt) when the truncated starting procedure is used, compared toO(Δt2) when consistent initial acceleration values are

ISSN:0098-8847    

DOI:10.1002/eqe.4290150710

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractExpected spectral ordinates and their standard deviations are computed for ground motions produced by SH waves at the surface of a homogeneous soil formation resting on a half‐space of rock. Wave transmission is idealized as linear and one‐dimensional. Uncertainties about soil properties are taken into account using various approximations: a Taylor series expansion of the Fourier spectrum magnification factors with different numbers of terms and different intervals for numerical differentiation; discretization of the joint probability density function of the soil properties so as to match its moments up to those of third order including the crossed moments; a discretization that matches up to some fifth‐order moments; and a fine numerical integration for the marginal density function of the modulus of rigidity, discretizing the rest of the density function. The latter approach gives sufficiently accurate results for practical purposes.Effects of even moderate uncertainty about soil properties on the statistics of spectral ordinates are found to be dec

ISSN:0098-8847    

DOI:10.1002/eqe.4290150711

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY