bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of earthquake ground motions using autoregressive moving average (ARMA) models
Authors: Polhemus N. W. , Cakmak A. S. 
Published: March 2007

AbstractParsimonious representations of recorded earthquake acceleration time series are obtained by fitting stationary autoregressive moving average models after a variance‐stabilizing transformation. Simulated acceleration series are then constructed by generating realizations from the fitted stationary models and applying the reverse transformation. As demonstrated on three components of a typical series, the response spectra for the observed and simulated series show good agreement for periods of less than eight seconds. Further, the model parameters for the three components are very similar, suggesting a consistency which could be useful for identifying site‐specific characteristics.
Analysis and prevention of suspension bridge flutter in construction
Authors: Brancaleoni F. , Brotton D. M. 
Published: March 2007

AbstractIt is known that the maximum danger of flutter‐type aerodynamic instability for suspension bridges occurs during the early erection phases of the deck.The effectiveness of two different provisional measures for increasing the instability critical windspeed in such conditions is evaluated for a long span suspension bridge with flat box stiffening girder.
The dynamics of a rigid foundation on the surface of an elastic half‐space
Authors: Hamidzadeh‐Eraghi H. R. , Grootenhuis P. 
Published: March 2007

AbstractThe response of a rigid rectangular foundation block resting on an elastic half‐space has been determined by considering first the displacement functions for any position on the surface of an unloaded half‐space due to a harmonic point force. The influence of the foundation has been taken into account by assuming a relaxed condition at the interface, i.e. a uniform displacement under the foundation and that the sum of the point forces must equal the total applied force. The three motions of vertical, horizontal and rocking have been considered and numerical values for the in‐phase and the quadrature components of the displacement functions are presented for a Poisson's ratio of 0.25. The effect of the mass and inertia of the foundation can be allowed for by an impedance matching technique. Response curves and non‐dimensional resonant frequency curves are given for a square and a rectangular foundation for different mass and inertia ratios and for several values of Poisson's ratio. These curves are for design purposes and are an addition to similar published curves for circular and infinitely long rectangular foundations. Some of the calculated results have been verified by a laboratory experiment.
Non‐parametric identification of a class of nonlinear multidegree dynamic systems
Authors: Masri S. F. , Bekey G. A. , Sassi H. , Caughey T. K. 
Published: March 2007

AbstractA non‐parametric identification technique is presented for chain‐like multidegree‐of‐freedom non‐linear dynamic systems. The method uses information about the state variables of non‐linear systems to express the system characteristics in terms of two‐dimensional orthogonal functions. The technique is applied to a model of a steel frame that has been extensively investigated both analytically and experimentally. The method can be used with deterministic or random excitation to identify dynamic systems with arbitrary non‐linearities, including those with hysteretic characteristics. It is also shown that the method is easy to implement and needs much less computer time and storage requirements compared to the Wiener‐kernel approach. The method is shown to have low sensitivity to the effects of additive noise in the experimental data.
Three‐dimensional hybrid modelling of soil‐structure interaction
Authors: Gupta Sunil , Penzien Joseph , Lin T. W. , Yeh C. S. 
Published: March 2007

AbstractA three‐dimensional hybrid model for the analysis of soil‐structure interaction under dynamic conditions is developed which takes advantage of the desirable features of the finite element and substructure methods and which minimizes their undesirable features. The modelling is achieved by partitioning the total soil‐structure system into a near‐field and a far‐field with a hemispherical interface. The near‐field, which consists of the structure to be analysed and a finite region of soil around it, is modelled by finite elements. The semi‐infinite far‐field is modelled by distributed impedance functions at the interface which are determined by system identification methods. Numerical results indicate that the proposed model makes possible realistic and economical assessment of three‐dimensional soil‐structure interaction for both surface and embedded structures.
An improved hammer‐impact technique for strong shear wave generation
Authors: Maiguma Teruki 
Published: March 2007

AbstractAs part of fundamental research on seismic energy sources, a series of experiments was made to improve the field procedures for producing SH waves by using the so‐called plank‐striking method and also to develop more adequate techniques to generate high‐energy shear waves. Based on the results obtained, a flexible impact device which is similar to a slingshot was made to apply a relatively strong impulse at the surface of the ground. This shear wave generator was demonstrated to have desired features in its low cost operation, easy repeatability, high reproducibility and relatively large output strength. Such a shear source, therefore, provides a useful means of evaluating dynamic characteristics of the foundation soils accurately and economically which can play an important role in current earthquake engineering.
The effectiveness of trenches in reducing seismic motion
Authors: May Thomas W. , Bolt Bruce A. 
Published: March 2007

AbstractThe effect of placing barriers in the travel path of P, SV and SH seismic waves has been studied using time‐domain solutions of plane‐strain finite element programs for two‐dimensional crustal models. The wavefields considered propagate parallel to the free surface of an elastic medium consisting of a single layer over a halfspace. Barriers take the form of open‐air trenches. Effects of damping are assessed by considering representative viscoelastic conditions. Computations are presented as the ratio of spectral energy observed at a point with the barrier system in place in the model to the spectral energy observed at the same point without the barrier system in the model. These spectral ratios are dependent upon the direction of wave propagation.The calculations brought to light the marked role of surficial layering and attenuation properties of the surface rocks or soils on the effectiveness of seismic trench barriers. Barrier models without these features cannot in general reliably predict seismic wavefields at the surface. In the range of cases studied, trench depth d rather than width is the most sensitive parameter. When the ratio d/λ, the ratio of trench depth to the wavelength of shear waves, is greater than about 0·6, power spectral ratios of 0·06 and less are found for SH waves and the vertical component of SV motion for frequencies of 4–6 Hz. By contrast, for frequencies less than 3–4 Hz, power spectral ratios from unity to about two and greater are observed, indicating amplification for the horizontal component of wave motion. Spectral ratios calculated at some locations in front of the barrier system show over two‐fold amplification. Spectral ratios also change significantly with the relative location of the free surface observation point.
Incremental time—space finite strip method for non‐linear structural vibrations
Authors: Cheung Y. K. , Lau S. L. 
Published: March 2007

AbstractBased on an incremental Hamilton's principle a versatile and systematic computer method for analysing non‐linear structural vibrations is developed in this paper. The essence of the proposed method can be regarded as an incremental harmonic balance method associated with a finite strip procedure in the time‐space domain. Only linearized equations in terms of frequency increment, amplitude increments, etc. have to be formulated and solved in each incremental step. This method is applicable to highly non‐linear problems and may be generalized to related non‐linear periodic structural motions such as dynamic stability, flutter and some motions of a rotating body, etc. To show the effectiveness and versatility of this method, a typical time‐space finite strip for beam problems is worked out and examples for a wide variety of vibration problems including free and forced vibrations, super‐ and sub‐harmonic resonances, and complicated phenomena such as internal resonance are computed. Comparisons with previous results are also made.
Non‐linear seismic response of arch dams
Authors: Niwa Akira , Clough Ray W. 
Published: March 2007

AbstractAn experimental study of non‐linear mechanisms that may occur during intense seismic response of arch dams is described in this paper. The presentation deals with three types of non‐linearity that were observed during shaking table model studies: monolith joint opening, cantilever cracking, and reservoir cavitation at the dam face.The monolith joint opening phenomenon was represented by a segmental arch ring model that simulated a horizontal slice of a prototype dam. The cantilever cracking and reservoir cavitation mechanisms were studied using a model gravity dam section. The principal conclusion of the investigation was that shaking table experiments provide a practical means of studying the non‐linear earthquake response of concrete arch dams, including their actual failure mechanisms.
Two‐dimensional dynamic analysis of concrete gravity and embankment dams including hydrodynamic effects
Authors: Hall John F. , Chopra Anil K. 
Published: March 2007

AbstractAn analysis procedure in the frequency domain is developed for determining the earthquake response of two‐dimensional concrete gravity and embankment dams including hydrodynamic effects; responses of the elastic dams and compressible water are assumed linear. The dam and fluid domain are treated as substructures and modelled with finite elements. The only geometric restriction is that an infinite fluid domain must maintain a constant depth beyond some point in the upstream direction. For such an infinite uniform region, a finite element discretization over the depth is combined with a continuum representation in the upstream direction. The fluid domain model approximately accounts for interaction between the fluid and underlying foundation medium through a damping boundary condition applied along the reservoir bottom, while the dam foundation is assumed rigid. Several examples are presented to demonstrate the accuracy of the fluid domain model and to illustrate dam responses obtained from the analysis procedure.
The response of veterans hospital building 41 in the San Fernando earthquake
Authors: Rutenberg Avigdor , Jennings Paul C. , Housner George W. 
Published: March 2007

AbstractDuring the 9 February, 1971 San Fernando earthquake, Building 41 of the Veterans Administration Hospital was in an area of very strong snaking; being directly over a portion of the causative fault; it is estimated that the building experienced a maximum base shear of 60 to 130 per cent of the weight of the structure. It survived with very minor structural damage, although designed with a lateral force coefficient of only 10 per cent. The study attempts to reconcile these facts by analysis of the transverse response of the building. A code‐oriented, lateral force analysis is only partially successful in this reconciliation in that it indicates first yield at lateral loads of 15–20 per cent of the weight of the structure, with a capacity of 35–45 per cent if redistribution of loads among the walls is permitted. The capacity against static overturning is 45–50 per cent. A dynamic analysis of a fixed‐base three‐dimensional linear model of the structure gives essentially the same results. A third study of a two‐dimensional, dynamic model incorporating partial uplift and soil yielding indicates that the successful response of the building is attributable to the large strength built into the structure and the beneficial effects of non‐linear soil‐structure interaction.
Optimum absorber parameters for various combinations of response and excitation parameters
Authors: Warburton G. B. 
Published: March 2007

AbstractIn recent papers the author has shown that when determining optimum parameters for an absorber which minimizes the vibration response of a complex system, the latter may be treated as an equivalent single degree‐of‐freedom system if its natural frequencies are well separated. Emphasis was on minimizing the displacement response when the excitation was a harmonic force. In the present paper simple expressions for optimum absorber parameters are derived for undamped one degree‐of‐freedom main systems for harmonic and white noise random excitations with force and frame acceleration as input and minimization of various response parameters. These expressions can be used to obtain optimum parameters for absorbers attached to complex systems provided that optimization is with respect to an absolute, rather than a relative, quantity. The requirement that the natural frequencies should be well separated is investigated numerically for the different cases. The effect of damping in the main system on optimum absorber parameters is investigated also.
Vibration tests on emosson arch dam, Switzerland
Authors: Deinum P. J. , Dungar R. , Ellis B. R. , Jeary A. P. , Reed G. A. L. , Severn R. T. 
Published: March 2007

AbstractMeasurements have been made of vibrations induced in the 180 m high Emosson arch dam in Switzerland3 by a system of mechanical eccentric‐mass vibrators and by the natural wind. Details are given of the dam itself, the tests and the experimental results obtained. Finite element calculations made before the tests, which include reservoir and foundation effects, are compared with the measurements.
Seismic design of flexible cylindrical liquid storage tanks
Authors: Balendra T. , Ang K. K. , Paramasivam P. , Lee S. L. 
Published: March 2007

AbstractSeismic response of cylindrical storage tanks anchored to rigid base slabs is considered. Finite elements are used for the liquid and tank wall, idealized as a thin shell. For steel tanks of practical dimensions, design charts are presented for natural frequencies, maximum shear and overturning moment on the foundation, and maximum stress resultants in the tank wall. Furthermore, an analytical expression for the superelevation of the free surface is presented.
Arma models for earthquake ground motions
Authors: Chang Mark K. , Kwiatkowski Jan W. , Nau Robert F. , Oliver Robert M. , Pister Karl S. 
Published: March 2007

AbstractThis paper outlines the use of discrete, autoregressive/moving‐average (ARMA) models for identification and estimation of parameters in models derived from analysis of uniformly digitized earthquake ground motion acceleration data. Such models are of equal generality as compared to continuous‐time models and have a number of significant advantages for purposes of digital analysis and simulation. The structure of ARMA models is briefly described, their relation to continuous models noted, and results of their application to a number of recorded accelerograms summarized.
Frequency domain analysis of time integration operators
Authors: Preumont A. 
Published: March 2007

AbstractThe present paper analyses the error associated with the time integration operators in structural dynamics. It considers the time integration operators as digital recursive filters. The transfer functions of the discretized equations are derived and compared with the transfer function of the differential equation. This leads to a new approach for the accuracy analysis of the time integration operators, which is not restricted to the homogeneous part of the discretized equation. It can therefore be applied to the Duhamel Integral for which, as far as the author is aware, no error analysis has been reported so far. Results are presented for the Newmark's family integration operators. Various assumptions on the variation of the excitation between the sampling points in the Duhamel Integral are also analysed.
Phase properties of a class of random processes
Authors: Nigam N. C. 
Published: March 2007

AbstractThe probability structure of the phase derivative of a class of random processes is derived in the time‐ and frequency‐domains. It is shown that in the time‐domain the phase derivative reflects the spectral properties of a stationary random process; whereas in the frequency‐domain the phase derivative reflects the non‐stationary character of a modulated white‐noise random process. The analysis provides a theoretical basis for the qualitative conclusions drawn in some recent investigations regarding the properties of the phase derivatives of earthquake ground accelerations.
Natural frequencies of arch dam reservoir system—by a mapping finite element method
Authors: Nath B. 
Published: March 2007

AbstractA simple mapping finite element method is used to calculate the coupled natural frequencies and mode shapes of realistic arch dam reservoir systems in which the dam is circular cylindrical with non‐uniform cross‐section. This method, in which both the dam and the reservoir domains are mapped into geometrically simpler shapes using cylindrical‐polar transformations, is found to give accurate results, achieved simply and economically.Results of analysis show that hydrodynamic interaction has a substantial effect on the coupled natural frequencies and mode shapes; also that the effect of water compressibility in the type of dams considered can be ignored without significant loss of accuracy. A simple method is also presented for predicting the water compressibility effect before undertaking detailed response analysis.
Modal damping for torsionally coupled buildings on elastic foundation
Authors: Balendra Thambirajah , Tat Chan Weng , Lee Seng‐Lip 
Published: March 2007

AbstractA method to determine the approximate normal modes and the modal damping for torsionally coupled buildings on an elastic foundation is presented. The modal damping is determined by an iterative procedure which matches the approximate normal mode solution with the rigorous solution. The response quantity to be matched is selected in a consistent and logical manner. The normal modes and the damping ratios thus found are then used to determine the seismic response of the interaction system by the response spectrum technique.
Dynamic analysis by direct superposition of Ritz vectors
Authors: Wilson Edward L. , Yuan Ming‐Wu , Dickens John M. 
Published: March 2007

AbstractThe solution of the eigenvalue problem for large structures is often the most costly phase of a dynamic response analysis. In this paper, the need for the exact solution of this large eigenvalue problem is eliminated. A new algorithm, based on error minimization, is presented for the generation of a sequence of Ritz vectors. These orthogonal vectors are used to reduce the size of the system. Only Ritz vectors with a large participation factor are used in the subsequent mode superposition analysis. In all examples studied, the superposition of Ritz vectors yields more accurate results, with fewer vectors, than if the exact eigenvectors are used. The proposed method not only reduces computer time requirements significantly but provides an error estimation for the dynamic analysis. The approach automatically includes the advantages of the proven numerical techniques of static condensation, Guyan reduction and static correction due to higher mode truncation.
Free‐field response from inclined SV‐ and P‐waves and Rayleigh‐waves
Authors: Wolf John P. , Obernhuber Pius 
Published: March 2007

AbstractTo identify the key features of the free‐field response for inplane motion, a vast parametric study is performed, varying the location of the control point, the nature of the wave pattern and the site properties. Harmonic excitation for a site consisting of a layer on bedrock is investigated.The nature of the wave pattern producing the site response is classified with respect to the apparent velocity of the motion propagating horizontally across the site. When the control point is selected at the outcrop of the bedrock, the amplification of the motion to the free surface of the site depends on the angle of incidence of the incoming wave in the bedrock. The amplification of the vertical motion for incident P‐waves hardly depends (with a tendency of being somewhat larger compared to vertical incidence) on the angle of incidence in the bedrock. The amplification of the horizontal motion for incident SV‐waves is affected strongly by the angle of incidence, being larger or smaller than for vertical incidence. Interpreting the two components of the motion at the free surface as arising from a combination of incident P‐ and SV‐waves leads to amplifications within the site (for the horizontal and vertical directions) which do not depend, from a practical point of view, on the angle of incidence and on the prescribed motion up to the fundamental frequency in the horizontal and vertical directions, respectively. The variation of the motion for the first Rayleigh‐mode with depth in the two directions bears comparison, in general, with that of vertically incident waves up to the corresponding fundamental frequency. The higher Rayleigh‐modes lead to a completely different variation with depth. In contrast to Rayleigh‐waves the attenuation of the motion in the horizontal direction for inclined body waves depends on the damping of only the bedrock. Rayleigh‐waves thus attenuate more strongly than body waves, especially in the higher‐frequency range. Generally, higher Rayleigh‐modes attenuate less than the first.
Rocking of slender rigid bodies allowed to uplift
Authors: Psycharis Ioannis N. , Jennings Paul C. 
Published: March 2007

AbstractStrong shaking of structures during large earthquakes may result in some cases in partial separation of the base of the structure from the foundation. A simplified problem of this type, the dynamic response of a rocking rigid block allowed to uplift, is examined here. Two foundation models are considered: the Winkler foundation and the much simpler ‘two‐spring’ foundation. It is shown that an equivalence between these two models can be established, so that one can work with the much simpler two‐spring foundation. Simple solutions of the equations of motion are developed and simplified methods of analysis are proposed. In general, uplift leads to a softer vibrating system which behaves non‐linearly, although the response is composed of a sequence of linear responses. As a result the apparent rocking period increases with the amount of lift‐off. The corresponding apparent ratio of critical damping decreases, in general, with the amplitude of the response. Compared to the case without lift‐off, the response of the system may increase or decrease because of the uplift, depending on the excitation and the parameters of the system.