摘要:

AbstractDynamic response of deeply embedded structures, such as underground tunnels and deep foundations, in a multilayered elastic half‐space are analysed when the structure is excited by a plane P or SV wave propagating at some angle. The scattered field is represented by the sum of three Green's functions, corresponding to two oscillating forces and one oscillating moment at the centroid position of the buried structure. The amplitudes of these two forces and one moment area prioriunknown and are obtained by satisfying displacement and stress continuity conditions across the near‐field/far‐field boundary. The distinguishing feature of this technique from direct or indirect boundary integral techniques is that in these techniques a distribution of sources of unknown amplitude are considered at the near‐field/far‐field boundary, and a large number of sources are needed for different combinations of source‐receiver arrangements. But in this technique the sources of unknown amplitude are placed at the location of the structure, not at the near‐field/far‐field boundary and, using the Saint Venant's principle, the scattered field is modelled. Thus, the number of sources required is reduced to only three. Two example problems are solved. The first one is for a deeply embedded footing in a three‐layer soil mass and the second one is for a rectangular tunnel in a tw

ISSN:0098-8847    

DOI:10.1002/eqe.4290220702

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractBased on a non‐linear dam‐reservoir interaction model, a study investigating the earthquake response of concrete gravity dams is presented. For the propagation of cracks in unreinforced mass concrete, a discrete crack approach formulation based on the finite element method is applied. A special crack element is used to follow a fictitious crack in order to account for a zone of microcracks developing at the crack tip. The reservoir is modelled using the boundary element method. At a fictitious boundary dividing the irregular finite part of the reservoir from the regular infinite part, the loss of energy due to pressure waves moving away towards infinity is taken into account rigorously. Analyses are performed on the tallest non‐overflow monolith of the Pine Flat Dam located in Kern County, California. The interaction of a dam, which may exhibit cracks in mass concrete, with a reservoir domain of arbitrary geometry extending to infinity is studied. Some main parameters are investigated. The importance of tools capable of handling the non‐linear dam‐reservoir interaction is e

ISSN:0098-8847    

DOI:10.1002/eqe.4290220703

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractOptimum isolation damping for minimum acceleration response of base‐isolated structures subjected to stationary random excitation is investigated. Three linear models are considered to account for the energy dissipation mechanism of the isolation system: a Kelvin element, a linear hysteretic element and a standard solid linear element, commonly used viscoelastic models for isolation systems comprising natural rubber bearings and viscous dampers. The criterion selected for optimality is the minimization of the mean‐square floor acceleration response. The effects of the frequency content of the excitation and superstructure properties on the optimum damping and on the mean‐square acceleration response are addressed. The study basically shows that the attainable reduction in the floor acceleration largely depends on the energy dissipation mechanism assumed for the isolation system as well as on the frequency content of the ground acceleration process. Special care should be taken in accurately modelling the mechanical behaviour of the energy dissipation de

ISSN:0098-8847    

DOI:10.1002/eqe.4290220704

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAn analysis of a recent modified frequency‐domain procedure for computing the response of linear systems using the fast Fourier transform (FFT) algorithm is described. This modified procedure eliminates the appended free‐vibration interval that is used in the standard approach. The duration of the period of computation still needs to be longer than that of the response interval of interest, but only slightly. Reducing the period of computation lowers the number of frequencies at which the transfer function needs to be defined. The major drawback of the method is a high sensitivity to errors in the computed values of the transfer function, which reduces the role of interpolation in the transfer function definition. The modified method is related to the discrete Laplace transf

ISSN:0098-8847    

DOI:10.1002/eqe.4290220705

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA design study has been conducted to explore the use of structural cladding panels with energy‐dissipating cladding‐to‐frame connections for seismic‐resistant design. The study identifies several issues involved in the modelling and analysis of frames with energy‐dissipating cladding‐to‐frame connections, establishes concepts for design, and provides a preliminary assessment of the force and deformation demands that are likely to be placed on panels and connections. Non‐linear dynamic analyses indicate that the clad frames perform well, based on observations about maximum interstorey drifts, maximum plastic hinge rotations in the frames, and maximum ductility demands on the cladding‐to

ISSN:0098-8847    

DOI:10.1002/eqe.4290220706

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe development of an efficient energy‐dissipating mechanism that works in conjunction with laminated elastomeric bearings in order to reduce the lateral deformation of the isolation system has always been a goal of base isolation research. Theoretically, this deformation will be reduced to the minimum if damping augmentation of the isolation system can reach a critical value. However, augmenting the isolation damping may cause some unwanted side effects. The purpose of this paper is to study the influence of isolation damping on the seismic response of heavily damped base‐isolated buildings. The base isolation system is assumed to be linearly viscoelastic and is analysed using the complex mode method. Solutions derived by using perturbation techniques for a two‐degree‐of‐freedom system and the computer simulation for a multiple‐degree‐of‐freedom system reveal that augmenting the isolation damping can reduce efficiently the deformation of the isolation system, but at the price of increasing the high‐frequency vibration in the superstructure. When the damping ratio of the isolation system is beyond some level, increasing the isolation damping will enlarge the extreme values of the base and superstructural accelerations. It is also found that approximate solutions derived from the use of classical damping and classical modes of vibration in the seismic analysis of heavily damped base isolation systems can be subst

ISSN:0098-8847    

DOI:10.1002/eqe.4290220707

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290220708

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290220701

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY