摘要:

AbstractForced vibration tests designed to isolate the effects of soil‐structure interaction are described and the results obtained for the nine‐storey reinforced concrete Millikan Library Building are analysed. It is shown that it is possible to determine experimentally the fixed‐base natural frequencies and modal damping ratios of the superstructure. These values may be significantly different from the resonant frequencies and damping ratios of the complete structure‐foundation‐soil system. It is also shown that forced vibration tests can be used to obtain estimates of the foundation impedance functions.In the case of the Millikan Library it is found that during forced vibration tests the rigid‐body motion associated with translation and rocking of the base accounts for more than 30 per cent of the total response on the roof and that the deformation of the superstructure at the fundamental frequencies of the system is almost entirely due to the inertial forces generated by translation and rocking

ISSN:0098-8847    

DOI:10.1002/eqe.4290160102

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe rate of convergence of the conventional mode superposition method can be significantly improved for systems subjected to relatively low frequency loadings by adding static correction terms to approximate the contribution of higher modes neglected by the use of a truncated eigenbasis. Two computational variants of the classical mode‐acceleration method are developed for that purpose. It is recommended that the pseudo‐static displacement correction vector should be computed from an expansion of the flexibility matrix in terms of the retained eigenvectors for actual computer implementat

ISSN:0098-8847    

DOI:10.1002/eqe.4290160103

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIt has been shown that the use of base isolation not only attenuates the response of a primary structural system but also reduces the response of a secondary system mounted on or within the main structure. The isolation system, superstructure and equipment may be made of different materials with significantly different energy dissipation characteristics such that the damping matrix for the combined system is non‐classical and can only be approximately expressed by modal damping ratios if the classical mode method is used for analysis. The object of this paper is to evaluate the accuracy of this procedure in approximating the responses of base‐isolated structures and internal equipment.The complex mode method can provide exact solutions to problems with non‐classical damping and is used here to find the exact response of the isolation‐superstructure‐equipment system. The entire system is assumed to be linear elastic with viscous damping and the superstructure is assumed to be proportionally damped so that the deformation of the superstructure can be expressed in terms of its classical modes. Recognizing that the ratio of the equipment mass to the structural mass and the ratio of the stiffness of the isolation system to the superstructural stiffness are both small, perturbation methods are used to find the response.This study shows that the response of base‐isolated structures can be determined by the classical mode method to some degree of accuracy, but the higher frequency content is distorted. The equipment response derived by the classical mode method is much smaller than the exact solution so that the complex mode method should be applied to find equipme

ISSN:0098-8847    

DOI:10.1002/eqe.4290160104

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper presents some comparative design results of typical structural systems in accordance with various code provisions, such as UBC and ATC‐03 of the U.S. and TJ‐11–78 of China. The solution comparisons are based on an optimization scheme for a given set of constraints and objective functions. Three levels of recursive procedures are employed in the algorithm to search for an optimum weight or construction cost including damages. Numerical examples are provided to compare the design results based on the aforementioned code provi

ISSN:0098-8847    

DOI:10.1002/eqe.4290160105

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA statistical analysis is performed to investigate the significance of peak ground acceleration to velocity ratio (a/v) on the displacement ductility demand of simple bilinear hysteretic systems. Three groups of earthquake records representative of low, normal and high

摘要:

AbstractThe finite and infinite element coupling system is used to study the effects of canyon topography and geological conditions on strong ground motion. The system is first applied to a semi‐cylindrical shaped canyon using SH wave propagation to verify its accuracy. It is concluded that different topography conditions may have important effects on the ground motions along the canyon. The geological conditions, by which we mean different softening of weathered strata of the canyon surface, will have significantly amplified effects on the free field motions. This fact suggests that a deep weathered rock excavation of arch dam abutments for stability purposes will also benefit earthquake resistance of the dam due to the reduction of ground motions of the sound roc

ISSN:0098-8847    

DOI:10.1002/eqe.4290160107

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn eigenfunction solution is presented for the dynamic response of vertical circular cylinders to earthquake excitation in a compressible fluid of finite depth. This single eigenseries expansion eliminates the need for a double summation over both the eigenfunctions and the trial functions as required by Rayleigh‐Ritz methods. Revised definitions for the added mass and hydrodynamic radiation damping coefficients per unit length are derived from the hydrodynamic fluid pressures. Based on comparisons between these newly defined coefficients, the compressibility of the fluid is found to be relatively more important at dimensionless frequencies greater than unity (ω>1.0) when analysing both rigid and flexible cylinders having relatively large diameter to water depth ratios,r0/h>0.25 (squatty type). This conclusion regarding the relative importance of the fluid compressibility is derived from a comparison between the relative magnitudes and the vertical distributions over depth of both the added mass and radiation damping coefficients per unit length for both rigid and flexible squatty cylinders. From additional comparisons with Rayleigh‐Ritz solutions that require trial functions, the results for totally immersed flexible slender cylinders (r0/h1.0 Hz) and below the first dimensionless cut‐off frequency for acoustic waves

ISSN:0098-8847    

DOI:10.1002/eqe.4290160108

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn analytical approach to calculate response spectra from seismological models of ground motion is presented. Seismological models have three major advantages over empirical models: (1) they help in an understanding of the physics of earthquake mechanisms, (2) they can be used to predict ground motions for future earthquakes and (3) they can be extrapolated to cases where there are no data available. As shown with this study, these models also present a convenient form for the calculation of response spectra, by using the methods of random vibration theory, for a given magnitude and site conditions. The first part of the paper reviews the past models for ground motion description, and introduces the available seismological models. Then, the random vibration equations for the spectral response are presented. The non‐stationarity, spectral bandwidth and the correlation of the peaks are considered in the calculation of the peak response. The accuracy of the model is found to be satisfactory after comparing the calculated spectra with the empirical spectrum of Joyner and Boore,51which was developed by using records from 12 shallow earthquakes in western North America. The last part of the paper presents some numerical examples that show the variation of response spectra and peak factors (i.e. peak response/RMS response) for different magnitudes and distance

ISSN:0098-8847    

DOI:10.1002/eqe.4290160109

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe direct integration method for structural systems having force and/or stiffness discontinuities is known to present considerable numerical difficulties. A non‐linear one‐degree‐of‐freedom test problem having these characteristics is developed and its exact oscillation period determined. The effects on amplitude and phase of small perturbations of the switching point, such as are caused by fixed‐step integration, have been studied. Artificial energy changes introduced at discontinuities by fixed‐step explicit and implicit methods are investigated. For a number of commonly used algorithms orders of convergence in fixed‐step integration of the test problem degrade from design value before, toO(h) after, the first discontinuity traversal.O(h) convergence is maintained for any number of discontinuity traversals thereafter, but design order can be recovered by locating the switching point sufficien

ISSN:0098-8847    

DOI:10.1002/eqe.4290160110

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290160111

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY