bluuebunny/crossref_metadata_2025_split huggingface dataset:
A methodology for locating strong motion arrays
Authors: Udwadia F. E. , Miura H. 
Published: March 2007

AbstractThis paper investigates a methodology for locating strong motion accelerographs in a seismically active region. Starting with the probability density of earthquakes in a given region, the paper attempts, within the framework of optimization theory, to formulate the following two questions: (1) given N accelerographs, where should they be located in a seismically active zone, and (2) having fixed these N accelerographs, where should the next M be located?Three different cost functions are presented. Some closed form solutions are illustrated for problems when N and M are small. For larger arrays, numerical optimization is resorted to.To demonstrate the methodology, a region with J faults, with given spatial locations is selected. An efficient algorithm for optimization is utilized and the technique illustrated. Good agreement with closed form solutions obtained in some simple cases is indicated. Specific application of the method to the placing of twenty strong motion instruments in a seismically active area has been carried out, and the patterns of sensor location, for each of the cost functions, illustrated.
Effects of seismic wave propagation upon buried pipelines
Authors: O'Rourke Michael J. , Castro Gerardo , Centola Naneen 
Published: March 2007

AbstractThe behaviour of long straight buried pipelines subjected to seismic wave propagation is investigated. Well‐known relationships for determining upper bounds for the axial strain and curvature in the pipeline as well as relationships for relative displacement and rotation at the pipeline joints are discussed. The assumption that the seismic excitation can be modelled as a travelling wave having a shape which remains unchanged as it traverses the pipeline is examined in detail. It is shown that this assumption is unconservative when the effective propagation velocity of the seismic waves with respect to the pipeline is such that the actual time lag (separation distance between points divided by effective propagation velocity) is less than a ‘cross‐over’ time lag. Cross‐over time lags for 22 pairs of ground displacements recorded during the 1971 San Fernando Earthquake are presented in this paper. Finally, methods for estimating the propagation speed of the seismic waves along or with respect to the pipeline are discussed.
Response of fixed offshore structures in random sea
Authors: Angelides Demosthenes C. , Connor Jerome J. 
Published: March 2007

AbstractAn integrated model is developed for the short‐term and long‐term dynamic response of an offshore structure subjected to random wave excitation. A discrete linear, elastic model of the upper structure is coupled with an iterative linear quasi‐three‐dimensional finite element model for the pile‐soil medium, and the system is subjected to stochastic storms described by mean rate of arrival, joint probability distribution of storm duration and average intensity, and a random process that describes the variations of a statistical wave height measure during each storm. Sarpkaya's 1977 experimental information is used to specify values for CM and CD, in Morison's equation, consistent with the flow and response characteristics. Soil (clay) degradation, due to cyclic excitation, is followed during the passage of a storm. The indicator of soil degradation is taken to be the value of the horizontal foundation stiffness and the stiffness degradation is modelled by a homogeneous Markov process.
A novel spherical polar finite element for the solution of the steady‐state scalar wave equation in three‐dimensions
Authors: Nath B. 
Published: March 2007

AbstractA novel method has been proposed for the finite element solution of the steady‐state scalar wave equation in three‐dimensions. In this the governing equation and the prescribed boundary conditions in the physical space are transformed into a spherical polar space in which the radial direction is logarithmically condensed; the physical problem domain is also mapped into the new space. The transformed equation is then solved in the mapped domain using conventional finite elements. Because physical dimensions of the problem are logarithmically condensed in the proposed spherical polar space, the method is particularly suitable for solving truly three‐dimensional problems in which the aspect ratio(s) is large or very large.A number of illustrative examples considered show that the proposed method is capable of a high degree of accuracy, achieved efficiently and economically. A hybrid scheme has also been proposed for dealing with awkward‐shaped domains.
Dynamic characteristics of lateral load‐deflection relationships of flexible piles
Authors: Kagawa Takaaki , Kraft Leland M. 
Published: March 2007

AbstractMost offshore platforms are supported on long and large‐diameter piles with variable wall‐thickness along the length, and soil properties varying with depth. The design and analyses of these piles are made by modelling the soil‐pile system with a beam‐on‐Winkler foundation. Therefore, evaluation of appropriate soil‐pile springs for use in such analyses is a matter of concern. Fundamental characteristics of dynamic lateral load‐deflection relationships for piles were studied analytically considering the soil‐pile‐structure interaction under seismic loading conditions. The soil layer was assumed homogeneous, linearly elastic with hysteretic type material damping, and overlying a rigid base. A superstructure with multi‐degrees of freedom was supported by a single vertical pile hinged at the rigid base.Parametric studies were carried out to identify the influence of the system parameters on the behaviour of the dynamic lateral load‐deflection relationships of piles. The lateral load‐deflection relationships vary considerably with depth and are influenced not only by the dynamic properties of soil but also by the structural properties of a pile and loading conditions. These lateral load‐deflection relationships can be used to define the soil‐pile springs for the seismic response analysis of a soil‐pile‐structure system, and the results can be extended to problems with soil profiles with layering and non‐linearity.
A linearization scheme for hysteretic systems subjected to random excitation
Authors: Grossmayer Rudolf L. , Iwan Wilfred D. 
Published: March 2007

AbstractThe problem of predicting the response of hysteretic yielding systems under random excitation is considered. The paper presents a linearization scheme which is motivated by extensive simulation studies of the bilinear hysteretic system. The response process is decomposed into a low frequency drift component and a component with a frequency near the linearized natural frequency of the system. Effective stiffness and damping parameters are presented. The accuracy of the various steps of the scheme is examined. The approach gives results which are in close agreement with simulation estimates even for large‐system non‐linearity.
On the moments of time to first passage of the linear oscillator
Authors: Bergman L. A. , Heinrich J. C. 
Published: March 2007

AbstractThe moments of time to first passage of the response process of the linear oscillator excited by a stationary wide‐band process are obtained numerically for the symmetric two‐sided barrier problem. A recursive set of partial differential equations governing the moments is solved using a Petrov‐Galerkin finite element method. Stable, accurate solutions for the first few moments are calculated over a wide range of oscillator damping.
An approximate method for soil‐structure interaction for sh‐waves—the born approximation
Authors: Chu L. L. , Askar A. , Cakmak A. S. 
Published: March 2007

AbstractAn approximate method is proposed for the scattering of SH‐waves by foundations of irregular shape and the resulting soil‐structure interaction problems. The scattering of elastic waves by the rigid foundation embedded in half‐space is solved approximately by using integral representation of the wave equation. The procedure is the Born approximation which has been widely used in quantum mechanics for collision and scattering theory though not well‐known in elastodynamics. This paper extends the previous work of the authors on the scattering of waves to account for soil‐structure interaction. The motion of the foundation is evaluated by the balance of momentum under stresses due to the incident waves as well as the waves generated by its own motion and the forces coming from the superstructure. The model investigated consists of an infinitely long elastic shear wall of height H and thickness h erected on a rigid infinitely long foundation. Results are presented for the cases with circular, elliptical and rectangular foundations. For a circular foundation, excellent agreement is found with the exact solutions for the foundation displacement and the relative displacement between the top and bottom of the structure for the entire range of wave numbers. For an elliptical foundation, accuracy decreases with increasing wave numbers. Foundation displacements are compared for foundation shapes that are shallow elliptical, deep elliptical, rectangular and circular. It is observed that foundation displacements are dependent on the angle of incidence except for a semi‐circle. The results on the details of the scattered field are, however, not as accurate.
Torsional instability in structures
Authors: Antonelli Richard G. , Meyer Keith J. , Oppenheim Irving J. 
Published: March 2007

AbstractTorsional instability under harmonic excitation was detected in structures with cubic softening member stiffness. A variational procedure was introduced to perform the analysis for the general problem formulation. Single‐storey structures with zero eccentricity were studied first; previous findings were checked and corrected, and the behaviour was examined in greater detail. Two‐storey structures with large eccentricity were also examined, and further regions of torsional instability were detected. Time history analysis was then employed to quantify the behaviour of various typical structures. An unbounded growth in rotation or column displacement was not observed. Rather, the instability appeared to be related to the jump in response which exists in single degree‐of‐freedom softening oscillators subjected to harmonic excitation. The practical significance of torsional instability is therefore rather weak, although prudent practice would recommend its avoidance.
Beam models for predicting dynamic elastic response
Authors: Neubert V. H. , Rangaiah V. P. 
Published: March 2007

AbstractFurther investigation of the three‐parameter lumped mass model for the prediction of natural frequencies and transient response of Bernoulli‐Euler clamped‐clamped beams has resulted in a revised model, which is slightly superior to the original model, as it is applicable over a wider frequency range.
Non‐parametric identification of a class of non‐linear close‐coupled dynamic systems
Authors: Udwadia F. E. , Kuo Chin‐Po 
Published: March 2007

AbstractA non‐parametric identification technique for the identification of arbitrary memoryless non‐linearities has been presented for a class of close‐coupled dynamic systems which are commonly met with in mechanical and structural engineering. The method is essentially a regression technique and expresses the non‐linearities as series expansions in terms of orthogonal functions. Whereas no limitation on the type of test signals is imposed, the method requires the monitoring of the response of each of the masses in the system. The computational efficiency of the method, its easy implementation on analogue and digital machines and its relative insensitivity to measurement noise make it an attractive approach to the non‐parametric identification problem.
Layered soil‐pile‐structure dynamic interaction
Authors: Takemiya Hirokazu , Yamada Yoshikazu 
Published: March 2007

AbstractThis paper is concerned with the dynamic interaction between soil, pile and structure when subjected to harmonic excitation at the base rock level. The structure to be analysed is an isolated tall bridge pier with deep group pile foundation. The dynamic substructure approach is taken, dealing first with the pile‐footing substructure and the pier superstructure independently; and then integrating these at the interface. Since the soil profile is multi‐layered, the transfer matrix scheme is applied to extend the relevant continuum solution proposed by earlier researchers for pile analysis in a homogeneous viscoelastic medium.Using a numerical example, the importance of the soil layer vibration modes which exert forces on the pile varying along the pile length is pointed out together with the soil‐structure inertial interaction in the structural response. The latter concerns the dynamic characteristic of the complete system whereas the former relates the driving force to it. Also examined is the applicability of the approximate soil reaction based on the plane strain assumption, which simplifies the formulation and requires much less computing time in the response analysis.
Impact study by various bridge models
Authors: Wiriyachai A. , Chu Kaung‐Han , Garg V. K. 
Published: March 2007

AbstractIn previous studies of train‐bridge interactions, impact percentages for member forces have been obtained by use of a pin‐connected truss model and for both member forces and moments by use of a rigid joint truss model. The purpose of this study is three‐fold: (a) to investigate if improved results can be obtained by use of semirigid connections at the ends of the floor beams and stringers; (b) to develop partial bridge models, for studying impacts and the range of forces and moments in members subjected to fatigue; (c) to employ a partial bridge model to study the influences of various factors on the impact factors and stress ranges of the various members and connections of the truss bridge. Descriptions of the bridge and vehicle models and the associated equations of motion are briefly stated, and results from the various bridge models are compared.
Energy dissipation and seismic liquefaction in sands
Authors: Ishac Magdi F. , Heidebrecht Arthur C. 
Published: March 2007

AbstractA statistical representation of seismic liquefaction is advanced based on the postulate that pore water pressure increases are proportional to the dissipated seismic energy density. The representation, based on approximately fifty case histories, relates the pore pressure increase to earthquake magnitude, distance to centre of energy release, initial effective overburden stressand standard penetration value. The model may be used for analysis ofseismic liquefaction risk. An example analysis for the ‘South of Market Zone’ in San Francisco is carried out in relation to earthquakes on the San Andreas fault.
Buckling of cylindrical liquid‐storage tanks under earthquake loading
Authors: Niwa Akira , Clough Ray W. 
Published: March 2007

AbstractThe earthquake response behaviour of a cylindrical wine storage tank similar to many that were damaged in Livermore, California during the January 1980 earthquake was studied on the University of California shaking table. Tests of the 9.5 ft diameter by 20 ft high tank, with simulated earthquake accelerations up to 0.95 g, induced buckling patterns similar to those observed after the actual earthquake. Observed peak axial compression stresses in the test tank wall were substantially higher than those assumed in typical design standards, demonstrating the need for further study of the buckling problem in tanks free to uplift during earthquake excitation.
Variability of tall building response to earthquakes with changing epicentre direction
Authors: Yang J. N. , Sae‐Ung S. , Lin Y. K. 
Published: March 2007

AbstractUsing a 40‐storey building as an example, the structural response under the excitation of horizontal earthquake ground motion is shown to vary greatly with the direction from the building site to the epicentre. Two mathematical models are used to represent the ground motion: the stationary random process model and the evolutionary‐type non‐stationary random process model. The former model is suitable if the duration of the most intense portion of an earthquake is much longer than the fundamental natural period of the structure. The maximum standard deviations of selected structural response quantities are computed and plotted for all possible epicentre directions, and the information is believed to be useful for design purposes.
Horizontally travelling waves in a group of piles taking pile‐soil‐pile interaction into account
Authors: Wolf John P. , von Arx Guido A. 
Published: March 2007

AbstractA reactor building founded on a large number of piles situated in a layered site is analysed for an historic earthquake assumed to be propagating horizontally. Pile‐soil‐pile interaction is properly accounted for, incorporating the frequency‐dependent stiffness and radiation damping. Compared to vertical incidence, the pile forces are increased and the piles close to the boundary are loaded more heavily than those in the centre region of the basemat.
Considerations on the residual contribution in modal analysis
Authors: Salmonte Antonio J. 
Published: March 2007

AbstractMode superposition has become a standard tool in the treatment of seismic analysis. Its advantages are appealing to the analyst. After years of widespread use of the method, it could be said that it is well understood, both in theory and application. However, its routine application can lead to errors caused by the analyst neglecting truly representative modes in the system response.In this paper, a very simple technique is suggested for representing, under certain conditions, the effect of the higher modes: the residual mode method. The effectiveness of the method in the context of response spectrum analysis is discussed, and such analysis is illustrated by a numerical example.
Local member response in offshore structures under earthquake excitations
Authors: Anagnostopoulos Stavros A. , Culbertson Arthur R. 
Published: March 2007

AbstractIt is pointed out that local vibrations of certain members in earthquake excited offshore structures can induce substantial stresses that may often dominate the design of these members. Such vibrations are not accounted for in dynamic analyses of structural models with masses lumped at the joints. A practical, easy to implement solution to this problem is recommended and results from an actual structure, subjected to a three‐component real earthquake, are presented demonstrating the importance of local inertia effects.
Diffraction of plane sh waves in a half‐space
Authors: Shah A. H. , Wong K. C. , Datta S. K. 
Published: March 2007

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 engineering.
Earthquake strong motions recorded by a large near‐source array of digital seismographs
Authors: Bolt B. A. , Tsai Y. B. , Yeh K. , Hsu M. K. 
Published: March 2007

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 ML 3·8 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 were large.
Lead‐rubber hysteretic bearings suitable for protecting structures during earthquakes
Authors: Robinson W. H. 
Published: March 2007

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 the size of the lead plug.
Dynamic characteristics of coupled wall‐frame systems
Authors: Basu Amiya K. , Dar Gulam Q. 
Published: March 2007

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 example.