摘要:

AbstractAverage and standard deviations of hypocentral distances to selected isoseisms are presented for Albania and Yugoslavia. The results apply for the Medvedev‐Karnik‐Sponheuer (MKS) intensity, provided that all data are corrected to a unified MKS equivalent intensity as defined by Shebalinet al.19The results should be useful in general macroseismic studies in these two countries, but are essential for the development of microzonation maps when the seismicity is described in terms of the locally available intensity catalogues.The observed attenuation of the intensities versus the hypocentral distance is similar to the attenuation of the Modified Mercalli Intensity (MMI) in the western United States of America. This finding should facilitate the use of other empirical scaling relations, developed in California, for various predictions of the characteristics of strong earthquake shaking in Albania and Yugosla

ISSN:0098-8847    

DOI:10.1002/eqe.4290180503

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA new method is introduced for the identification of modal quantities of self‐adjoint distributed‐parameter systems. The method uses the temporal and spatial orthogonality properties of distributed‐parameter systems to form a pseudo‐Rayleigh quotient. The stationary values of the pseudo‐Rayleigh quotient can be determined by the solution of an eigenvalue problem, where the eigenvalues and eigenfunctions provide the frequencies and natural modes of the distributed‐parameter system. By way of formulation, the method is insensitive to zero mean measurement noise and is applicable to continuous as well as discrete systems. Numerical examples are presented in which the modal quantities of a simply‐supported beam and a discrete model of a membrane are identified. The results are compared with another modal identification technique, namely, the Ibrahim time

ISSN:0098-8847    

DOI:10.1002/eqe.4290180504

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAn explicit predictor‐corrector algorithm is derived from the implicit α‐method. This explicit algorithm is shown to have better stability and accuracy properties than its Newmark‐based predecessor. This algorithm is then combined with the implicit α‐method, resulting in an implicit‐explicit α‐method which can be effectively utilized for linear and non‐linear structural dynam

ISSN:0098-8847    

DOI:10.1002/eqe.4290180505

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractLocal incremental stiffness relations are formulated for a class of elasto‐plastic beam elements. The earthquake acceleration is modelled as a filtered white noise process. The Itǒ differential equations of the integrated system made up of the structural system and the excitation process are then formulated. Instead of the original system an equivalent nonlinear system is considered, in which the drift vector is given by a series expansion of ordern≧ 1, wheren= 1 represents the well‐known case of equivalent linearization. Only components of the drift vector representing the non‐analytieal constitutive equations are replaced by a polynomial expansion. The coefficients of this expansion are determined from a least mean square criterion, and are sequentially updated. Especially an equivalent system with a cubic expansion to the drift vector is investigated. The hierarchy of statistical moment equations is closed by a cumulant neglect closure scheme. The method has been applied to a two‐storey frame. The results are compared to those of numerical simulation, and provide substantial improvements compared to equivalent lin

ISSN:0098-8847    

DOI:10.1002/eqe.4290180506

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe total system studied in this paper is a layered soil stratum with a rigid bedrock and a cylindrical cavity on the surface. Analytic solutions for the layered medium with prescribed harmonic displacement time history on the surface of the cylindrical cavity are presented. The whole soil domain is divided into interior and exterior domains. The interior domain is the projection of the cylindrical cavity down to the rigid bedrock, whereas the exterior domain is then the soil medium complement to the interior domain. The displacement and stress fields in both domains are expanded as an infinite series of Fourier components with respect to the azimuth. For each Fourier component in the infinite series, the solutions for both domains are found independently by solving the general differential equations of wave propagation satisfying the boundary conditions of the top surface and the lower rigid boundary. Displacement and stress continuity conditions are then imposed on the vertical interface between the two domains using the formulation of a weighted residual. For the soil‐structure interaction problem, the impedance matrix at the interface between the structure and the soil medium can be easily generated using the analytic solutions, which can then be combined with the finite element model of the structure. A simple example is presented to demonstrate the effectiveness of the procedure presente

ISSN:0098-8847    

DOI:10.1002/eqe.4290180507

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper examines the dynamic implications of connecting closely neighbouring structures for the purpose of eliminating pounding during earthquakes. To prevent this destructive contact the structures are connected by a link and beam system which transmits the connection forces to the floors of the structures. Four specific cases are used as examples of the effects.The coupled system is modelled as a combined mass and stiffness matrix problem which allows the traditional methods for analysis. The mode shapes and natural frequencies for these cases are examined, and it is shown that the general response characteristics can be derived from the coupled system's frequencies and modes. Estimates of the fundamental frequency of the coupled system are derived. Both the harmonic and earthquake response are examined for the four cases. In all circumstances the linkage reduces the relative overlap deflection of the structures at large amplitudes, but it also increases the base shear on the stiffer of the two structures at excitation frequencies below the fundamental frequency. It is shown that bounds on the base shear are derivable from the change in the fundamental frequencies. The dependence of the response characteristics on the stiffness of the coupling beam is also examined.

ISSN:0098-8847    

DOI:10.1002/eqe.4290180508

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe dynamic responses of three deck‐type arch bridges, with main spans of 59,213 and 518m, are presented. The ratios of natural period to arch span were found to be quite close for all three bridges. Artificial ground motions were applied separately in three directions to finite‐element models of each bridge. Three acceleration levels were considered—0.09g, 0.22gand 0.50g—corresponding to the AASHTO Seismic Risk Zones I, II and III, respectively. Responses to uniform lateral motion were generally the largest, while the responses to vertical motion were generally lower than those due to lateral or longitudinal motion. In all cases considered, none of the total stresses in the main members exceeded the yield stress. Connection and secondary member responses were also calculated and are presented. In addition, the effects of unequal motions at the supports were sampled by various deterministic inputs. While the effects of such motions in the vertical and lateral directions were less than the responses to uniform motion, the effects of unequal longitudinal motions at the supports were subs

ISSN:0098-8847    

DOI:10.1002/eqe.4290180509

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe objective of this paper is to propose an FFT technique symmetrical for time and frequency, in which the symmetrization is done by introducing generating functions. By the symmetrical treatment, it becomes possible to derive several complementary relations in the time and frequency domains. Based on the idea of the symmetrical FFT technique, the phase problem of seismic waves is discussed not only in the frequency domain but also in the time domain. Furthermore, the deconvolution technique to evaluate the minimum‐phase‐shift and all‐pass functions of seismic waves, which is not discussed sufficiently in earthquake engineering, is developed in the two domains. Numerical examples to present these basic ideas are also illustrated in the symmetrical fram

ISSN:0098-8847    

DOI:10.1002/eqe.4290180510

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA new experimental method using a finite soil model with no special treatement on its boundaries is employed for soil‐structure intration problems to simulate the semi‐infinitenesss of the actual soil medium. The present method utlizies the characteristics of transient response to an impluse load to obtain the impedance functions and effective input motions for surface and embedded foundations. This technique is applicable to a linear elastic system whose impulse response decreases to a small enough value before observing the reflected waves. The experimentally obtained impedance functions and effective input motions are compared with those obtained by the direct boundary integral equation method and the hybrid approach. Good agreement between the xperimental and analytical results validates the present method as well as the accuracy of the numerical to

ISSN:0098-8847    

DOI:10.1002/eqe.4290180511

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290180512

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY