摘要:

AbstractSoil amplification characteristics of earthquake ground motion were investigated in terms of peak ground acceleration and transfer function based on the Chiba array observation records. The amplification of peak ground acceleration occurred mostly at the top soft layer and was similar for the three components. The effects of non‐linear response of soil deposits on the transfer function were examined. Transfer functions calculated by ensemble average were close for the two horizontal components while those obtained from a smoothing operation were generally different. Both the transfer functions from the ensemble average and the smoothing operation underestimated the gain factor around the natural frequencies. A two‐step smoothing procedure was proposed and a rotary spectrum was used to improve the estimation of the transfer function. Microtremors were observed at the locations of the boreholes where seismometers are buried. The power spectrum and spatial coherency of the microtremors were compared with those of the earthquake ground motion. Emphasis was placed on the wavetypes which dominated the peaks in the power spec

ISSN:0098-8847    

DOI:10.1002/eqe.4290210201

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA general theory of mode combination is developed for structural systems subjected to stationary stochastic excitation. The analysis begins with a brief review of a mode combination expression for first‐order systems. Then, new fundamental properties of this result are developed. These properties are used to establish common analytical foundations and make new extensions of previously developed mode combination results for under‐critically damped, classically damped, cascaded and non‐linear structures. In the second part of the paper, an efficient and general mode combination method is developed for cascaded structures. It is shown how the unified mathematical framework established herein can be applied to cascaded structures composed of different types of substructures without the need to derive separate mode combination expres

ISSN:0098-8847    

DOI:10.1002/eqe.4290210202

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe system damping, the system frequency, the relative building response and the base rocking response peak amplitudes are studied, as those depend on the building mass and height, the flexibility of the soil, the structural damping, the type of incident waves and their angle of incidence. A linear two‐dimensional model is used, which assumes the soil to be a homogeneous isotropic half‐space, the foundation supporting the building to be a rigid embedded cylinder, and in which the building model is an equivalent single‐degree‐of‐freedom oscillator. The system frequency and the system damping ratio are determined by measuring the width and the frequency of the peak in the transfer function of the oscillator relative response, using the analogy with the half‐power method for a single‐degree‐of‐freedom fixed‐base oscillator. Previous similar studies are for dynamic soil‐structure interaction only, and for simplified models in which the stiffness of the soil and the damping due to radiation are represented by springs and dashpots. The study in this paper differs from the previous studies in that the wave passage effects (or the kinematic interaction) are also included, and that no additional simplifications of the model are made. Results are shown for excitation by

ISSN:0098-8847    

DOI:10.1002/eqe.4290210203

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA simplified three‐step procedure is proposed for estimating the dynamic interaction between two vertical piles, subjected either to lateral pile‐head loading or to vertically‐propagating seismic S‐waves. The starting point is the determination of the deflection profile of a solitary pile using any of the established methods available. Physically‐motivated approximations are then introduced for the wave field radiating from an oscillating pile and for the effect of this field on an adjacent pile. The procedure is applied in this paper to a flexible pile embedded in a homogeneous stratum. To obtain analytical closed‐form results for both pile‐head and seismic‐type loading pile‐soil and soil‐pile interaction are accounted for through a single dynamic Winkler model, with realistic frequency‐dependent ‘springs’ and ‘dashpots’. Final‐ and intermediate‐step results of the procedure compare favourably with those obtained using rigorous formulations for several pile group configurations. It is shown that, for ahomogeneousstratum, pile‐to‐pile interaction effects are far more significant underhe

ISSN:0098-8847    

DOI:10.1002/eqe.4290210204

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractComputational algorithms based on the pseudo‐force method (PFM) and the tangent spectrum method (TSM) for the seismic analysis of elasto‐plastic MDOF structures by mode superposition are presented. The emphasis is put on the effect of the truncation of higher modes on the convergence of the ductility demand and energy dissipated during the earthquake. Eigenvectors and load‐dependent vectors have been used in comparative analyses. Applications on a flexible 25‐storey building and a stiff, 5‐storey shear building indicate that, for a flexible structure, the ductility demand computed from the PFM is more sensitive to basis truncation than that computed from the TSM. However, for the stiff structure, the opposite behaviour is observed. The results indicate that the use of load‐dependent vectors in inelastic analyses maintains the computational advantages found for elastic analyses in previous investigations. Although the PFM is more stable and computationally more effective than the TSM, it does not provide any information on the evolution of tangent modal properties in time that reflects dynamic response modification as the structure become

ISSN:0098-8847    

DOI:10.1002/eqe.4290210205

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210206

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210207

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY