摘要:

AbstractScattering of antiplane shear waves (SH) in two dimensions by surface and near‐surface defects in a homogeneous, isotropic elastic semi‐infinite medium has been studied. Attention has been focused here in the range of medium to long wavelengths. A combined finite element and analytical technique has been used to study the problems of scattering by semi‐circular and triangular canyons. The results for the former case are compared with the known exact solution and those for the latter case are compared with some available approximate solutions. Finally a problem of multiple scattering by a triangular canyon and a nearby circular tunnel is studied. Numerical results are presented showing the effects of multiple scattering and different angles of incidence. These results are of interest in earthquake engine

ISSN:0098-8847    

DOI:10.1002/eqe.4290100402

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA direct approach to the integration of accelerometer data is presented which depends only on the fact that the final velocity and possibly, the final displacement are known. Using a dynamic programming formulation, the accelerometer record is corrected to account for these cases. The formulation is presented for the general case where velocity, displacement, as well as accelerometer data, are available. A numerical example is included.

ISSN:0098-8847    

DOI:10.1002/eqe.4290100403

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe dynamic analysis of complex non‐linear structural systems by the finite element approach requires the use of time‐step algorithms for solving the equations of motion in the time domain. Both an implicit and an explicit version of such a time‐step algorithm, called the ρ‐method, the parameter ρ being used for controlling numerical damping in the higher modes, are presented in this paper. For the implicit family of algorithms unconditional stability, consistency, convergence, accuracy and overshoot properties are first discussed and proved. On the basis of the algorithmic damping ratio (dissipation) and period elongation (dispersion) the ρ‐method is then compared with the well‐known implicit algorithms of Hilber, Newmark, Wilson, Park and Houbolt. An explicit version of the algorithm is also derived and briefly discussed. This shows numerical properties similar to the central difference method. Both versions of the algorithm have been implemented in a general purpose computer program which has been often used for both numerical tests and practica

ISSN:0098-8847    

DOI:10.1002/eqe.4290100404

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractCertain materials have different elastic behaviour when they are loaded in tension as compared to compression. As an engineering approximation, they are usually modelled as a bimodular material, i.e. a bilinear material having different Young's moduli in tension and in compression. All of the previous analyses of bimodular beams known to the present investigators have been concerned with either static loading or harmonic vibration. Thus, the present work is believed to be the first to consider transient response of such beams. The transfer‐matrix method is used to discretize spatially, while the timewise discretization is accomplished by use of the Newmark beta metho

ISSN:0098-8847    

DOI:10.1002/eqe.4290100405

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractSpecially designed arrays of strong‐motion seismographs near to the earthquake source are required for seismological and engineering studies of the generation and near‐field properties of seismic waves. The first such large digital array, called SMART 1 (with radius 2 km and 37 accelerometers), to record substantial ground motion (up to 0·24g horizontal acceleration) became operational in late 1980 in a highly seismic region of Taiwan. During the first 6 months of operation, SMART 1 recorded nine earthquakes with magnitudes ranging from ML3·8 to 6·9. Three were located directly below the array at focal depths of 59 to 76 km. The remaining six had shallow depths and epicentral distances from 7 to 193 km. Digital records from 27 three‐component accelerographs were obtained from a magnitude 6·9 (ML) local earthquake on 29 January 1981. Representative measurements are described of seismic wave coherency and power spectrum as a function of wave number, frequency, azimuth of propagation and wave type. Acceleration waveforms varied significantly across the array for each event. On average, peak acceleration of horizontal components was about three times that of the vertical component. Relative spectral changes from earthquake to earthquake w

ISSN:0098-8847    

DOI:10.1002/eqe.4290100406

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractPresented are the results of engineering analyses of selected accelerograms recorded by the SMART 1 strong motion array in Taiwan which is described in a companion paper by B. A. Bolt, Y. B. Tsai, K. Yeh and M. K. Hsu, entitledEarthquake Strong Motions Recorded by a Large Near‐source Array of Digital Seismographs.These analyses include (1) transformations to principal axes, (2) generation of Fourier amplitude spectra, (3) development of generalized response spectrum ratios for characterizing multi‐support excitations and (4) moving window analyses in the time and frequency domains for studying the spatial variations of recorded ground moti

ISSN:0098-8847    

DOI:10.1002/eqe.4290100407

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractLead‐rubber hysteretic bearings provide in a single unit the combined features of vertical load support, horizontal flexibility and energy absorbing capacity required for the base isolation of structures from earthquake attack. The lead‐rubber hysteretic bearing is a laminated elastomeric bearing of the type used in bridge structures, with a lead plug down its centre.Since the invention of the lead‐rubber bearing, a total of eleven bearings up to a diameter of 650mm, with lead plugs ranging from 50 to 170mm in diameter, have been tested under various conditions, including vertical loads to 3·15 MN, strokes to ρ 110 mm, rates from 1 mm/h to 100 mm/s, and temperatures of −35°C to + 45°C. In all of these tests, the lead‐rubber bearings behaved satisfactorily and the hysteresis loops could be described reasonably well by assuming that the lead behaved as an elastic‐plastic solid with a yield stress in shear of 10·55 MPa. The bearings showed little rate dependence at ∼100 mm/s, though at creep rates of ∼1 mm/h the force due to the lead dropped to 30 per cent of that at typical earthquake frequencies. The effect of many small displacements has been tested with 11000 cycles at ±3 mm. A total of 92 lead‐rubber bearings have been used in New Zealand to base isolate one building and three bridges. They have yet to be used overseas.This paper describes the tests on the lead‐rubber bearings, the results and a design procedure for selecting

ISSN:0098-8847    

DOI:10.1002/eqe.4290100408

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractIn this study the seismic risks of northern Iraq have been evaluated by a probabilistic method. The data contain about 500 earthquakes which occurred between 1840 and 1978. The epicentral locations and magnitudes of the included earthquakes have been presented.A linear relationship between magnitude and frequency has been assumed. The attenuation of intensities has been presented as a function of magnitude and epicentral distance.The seismic risk has been calculated for 225 points of the analysed area. The equiseismal maps related to a certain risk level have been plotted by using these point values of intensities, and assuming a linear variation between the points. The significance of the standard deviation of the attenuation law and the strict lower bound intensity has been investigated by sensitivity analyses.The intensity contours related to the annual return period of 50, 100 and 200 years have been presented, and also the intensity contours with an occurrence probability of 10 per cent during 50, 100 and 200 years have been drawn.

ISSN:0098-8847    

DOI:10.1002/eqe.4290100409

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe paper presents the first three natural frequencies and the corresponding mode shapes for fixed‐base multistorey buildings which can be idealized as an equivalent planar coupled shear wall connected in series to an equivalent frame. The coupled wall is modelled as a continuum of uniform properties and the frame as a uniform shear beam, the connection between the two elements being taken as continuous. Solutions are obtained by treating the structure as a lumped parameter system with twenty equidistant discrete masses having only translational inertia. The relevant flexibility matrix is, however, generated from the exact solution of the governing differential equation for the continuum subjected to point loading. The results are presented for various combinations of the three non‐dimensional parameters which are sufficient to describe all the geometric and material properties of the system. The mode shapes are presented in terms of the first three normal modes of a uniform slender cantilever. The non‐dimensional base shears required for the response spectrum analysis of buildings of the type under consideration are also given for the three modes and for the various combinations of the three non‐dimensional parameters mentioned above. The use of the results is illustrated by an

ISSN:0098-8847    

DOI:10.1002/eqe.4290100410

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290100412

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY