bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of shaking table‐structure interaction effects during seismic simulation tests
Authors: Blondet Marcial , Esparza Carlos 
Published: March 2007

AbstractAn analytical model is developed to evaluate performance characteristics of unidirectional seismic simulators (shaking tables). The validity of the model is verified with experimental measurements of the frequency response of the shaking table at the Catholic University of Peru.Interaction effects between shaking table and structure are first studied by analysing the response of a two DOF (degree of freedom) oscillator with mechanical properties representative of the actuator‐table‐structure system. A single DOF viscoelastic oscillator representing the structural test specimen is then included in the analytical model of the seismic simulator, and the behaviour of the combined system is evaluated, in the frequency domain, in terms of response stability and accuracy of reproduction of the command signal. Numerical simulations of system response under different load conditions are subsequently performed in order to study the influence of shaking table and test structure characteristics on the interaction phenomenon.The results obtained explain some of the performance degradation observed in seismic simulation tests involving very heavy structures and provide guidelines for the design of more reliable shaking table systems.
Decoupled dynamic analysis of combined systems by iterative determination of interface accelerations
Authors: Spanos P. D. , Cao T. T. , Jacobson C. A. , Nelson D. A. R. , Hamilton D. A. 
Published: March 2007

AbstractA dynamic analysis technique is presented that can be used to determine the response of a discrete model of a large linear structural system composed of multiple substructures. The technique circumvents the costly computation of the modal characteristics of the combined system. This is accomplished by relying on a predictor‐corrector scheme to converge iteratively to the interface accelerations of the combined system, while the equations of motions of the individual structures are integrated separately. In this regard, the temporal slopes of the interface accelerations (jerks) are computed at each time point of integration to predict the interface accelerations at the next time point. The proposed technique is exemplified by conducting a space shuttle landing loads analysis; the obtained numerical data demonstrate its reliability and efficiency.
Vibration control of structures under earthquake loading by three‐stage friction‐grip elements
Authors: Roik K. , Dorka U. , Dechent P. 
Published: March 2007

AbstractThe behaviour of a building subjected to a strong‐motion earthquake depends highly on its energy dissipation capacity. By introducing three‐stage friction‐grip elements, the energy dissipation within each storey can be ‘designed’ according to definable stages (e.g. serviceability, medium‐ and strong‐motion earthquake). Tests on simple steel‐concrete‐ and steel‐steel‐friction‐grip connections have proved their very satisfactory behaviour under high dynamic loading, showing no considerable damage when well designed. Examples of horizontal stiffening elements are given to illustrate the construction of three‐stage elements with either steel‐steel‐ or steel‐concrete‐friction‐grip joints.By computing the response of a seven storey building designed as a steel frame (‘ductile system’ philosophy), concrete core (‘stiff system’‐philosophy) and three‐stage truss and being subjected to the 1940 El Centre earthquake, the superior performance of three‐stage elements and its economic advantage over the other two systems becomes apparent. Although this is just one illustrative example, it is nevertheless an important one, because it resembles the type of building that would respond best to the application of three‐stage building brakes. Finally, the result of an online test on a three‐stage element is given. This realistic earthquake simulation proved the behaviour to be adequately close to the basic philosophy and yielded important design implications for three‐stage elements.
Optimum design of single‐frequency dynamic dampers
Authors: Ebrahimi Nader D. 
Published: March 2007

AbstractThe problem of damping the vibration amplitude of machines and structures has considerable practical importance. This paper discusses the design of optimum vibration absorbers for linear damped systems operating at a certain excitation frequency. The problem is first formulated as a mathematical programming scheme. The systematic design discussed in this paper has significant advantages for those vibratory systems run primarily at a specific frequency.
Elastic‐plastic response spectra for different hysteretic rules
Authors: Minami Tadao , Osawa Yutaka 
Published: March 2007

AbstractThe general features of elastic‐plastic response spectra for several accelerograms that are widely used for the design buildings in Japan were studied in terms of the effects of the different hysteretic models used in the analyses. Lare fluctuations existed in the spectra for both input ground motion and the different models. The models were classified according to their strain energy‐absorbing capacities in three groups, within each of which the relevant nature of elastic‐plastic responses of the structures were similar. Finally, empirical formulae with which to estimate two measures structural damage, the ductility factors and cumulative plastic displacement normalized by the yielding displacement, wer developed for each group of hysteretic models.
Criterion of stability and implementation issues of hybrid frequency‐time‐domain procedure for non‐linear dynamic analysis
Authors: Darbre Georges R. , Wolf John P. 
Published: March 2007

AbstractA criterion of stability pertaining to the hybrid frequency‐time‐domain procedure is derived. It stems from the initial‐value theorem on one side and from the condition of convergence which applies to the harmonic counterpart of the procedure on the other side. The criterion depends on the dynamic stiffnesses of both the original non‐linear system and the pseudo‐linear system evaluated at the Nyquist frequency. Since at this frequency both stiffnesses are usually controlle by the mass, the criterion of stability is satisfied for most structural systems. The procedure must, however, be applie sequentially to individual time segments. The validity of this criterion is confirmed by a numerical investigation performe for a SDOF system.The solution of non‐linear dynamic problems requires consideration of implementation issues which are also discusse in the paper. The analysis of a non‐linear soil‐structure‐interaction system in which the soil's stiffness coefficients an directly defined in the frequency domain also demonstrates the accuracy of the hybrid frequency‐time‐domain procedure.
Spatial variation and stochastic modelling of seismic differential ground movement
Authors: Loh Chin‐Hsiung , Yeh Yeong‐Tein 
Published: March 2007

AbstractSpecially designed arrays of strong motion seismographs located near earthquake sources are required for engineering studies of near‐source earthquake properties as well as spatial variation of seismic waves. The SMART‐1 array in Tath provides good records for this type of study. Based on the SMART‐1 array data, the analysis of the principal direction wave propagation and the space‐time correlation of some events recorded by SMART‐1 have been studied. A stoce model for predicting the differential ground movement was also developed. This stochastic model includes the effect of source characteristics, attenuation of wave passage and spatial correlation characteristics. The performance of this more discussed and compared with the ground movement recorded by the SMART‐1 array. From the present study, it is that spatial correlations do exist as seismic waves propagate across the array site. Generally, the loss of coherence is direction of propagation can be explained by energy at the same frequency exhibiting a slightly different velocity with the measurement intervals. It is also concluded that the phase velocity of seismic waves and the corner frequency of the grep displacement spectrum are controlling factors in the prediction of the root mean square of differential grep displacement.
Implementation of effective seismic input for soil‐structure interaction systems
Authors: Cremonini Marco G. , Christiano Paul , Bielak Jacobo 
Published: March 2007

AbstractA previously introduced method for transmitting effective seismic excitation to a discretized soil‐structure system implemented. The method permits free‐field excitation of a linear soil system to be specified within the regie of computation, arbitrarily close to a zone that includes the (possibly non‐linear) structure and local subgrade and bae, thus eliminating the need to transmit the seismic excitation through artificial boundaries. This approach is demonse through a numerical example comprising a linear, two‐dimensional system. Some comments also are made on the rere efficiencies of various local absorbing boundaries.
Fluid‐structure interaction effects for offshore structures
Authors: Veletsos A. S. , Prasad A. M. , Hahn G. 
Published: March 2007

AbstractComprehensive analyses are made of the differences in the responses of simple models of offshore structures computed by the standard and extended versions of Morison's equation for the hydrodynamic forces, and of the effects and relative importance of the numerous parameters involved. The responses also are evaluated by the equivalent linearization technique and Penzien's decoupling technique, and the interrelationship and accuracy of these approaches are elucidated. The results are displayed graphically in the form of response spectra for absolute maximum displacement employing dimensionless parameters that are easy to interpret and use. In addition, the decoupling technique is generalized to include consideration of a current of constant velocity, and a simple modification is proposed which improves the accuracy of this approach. A particularly simple approximation is included for the hydrodynamic modal damping values of multi‐degree‐of‐freedom, stick‐like systems.
Modal superposition method for seismic design of non‐linear multistorey structures
Authors: Villaverde Roberto 
Published: March 2007

AbstractAn approximate procedure is introduced to analyse non‐linear multistorey structures within the framework of the conventional response spectrum method. Its derivation is based on the use of non‐linear response spectra and an approximate decomposition of the equation of motion for multi‐degree‐of‐freedom non‐linear systems. The decomposition is attained by considering the non‐linear terms in this equation of motion as additional external forces and, thus, by interpreting it as the equation of motion of linear systems with the initial properties of the non‐linear ones when subjected to a modified set of inertia forces. For simplicity, the procedure is herein limited to elastoplastic systems of the shear‐beam type. Its accuracy is evaluated by comparing the approximate and step‐by‐step integration solutions of systems with three and ten degrees of freedom when subjected to three different earthquake ground motions.
Response of a randomly inhomogeneous layer overlying a homogeneous half‐space to surface harmonic excitation
Authors: Hryniewicz Z. , Hermans A. J. 
Published: March 2007

AbstractThe paper is concerned with the study of the effect of the randomness of material parameters on mean wave propagation in a semi‐infinite viscoelastic medium. The medium considered in this paper is a configuration of a randomly non‐homogeneous layer overlying a homogeneous half‐space and is loaded harmonically on the top surface. The method used is that of Karal and Keller and is based on the idea of fundamental matrix and Bourret approximation. The integro‐differential equation obtained in this paper is solved by the Laplace transform method. By using boundary and continuity conditions the mean wave solution is obtained. Numerical results show that the correlation functions, which introduce long‐range interactions, can be the source of the wave amplification.
A solution procedure for the earthquake analysis of arch dam‐reservoir systems with compressible water
Authors: O'Connor J. P. F. , Boot J. C. 
Published: March 2007

AbstractTwo processes using the Newmark implicit integration scheme are presented for the analysis of the earthquake response of a three‐dimensional model for arch dam‐reservoir systems including the effect of compressibility of the water. The solid structure and fluid regions are modelled separately, and the forcing functions at the interface are due to the hydrodynamic pressures from the reservoir acting on the upstream face of the dam wall, and the accelerations from the dam wall acting in turn on the reservoir.For the purposes of an initial investigation, elastic properties are assumed for the material of the dam, whilst in the reservoir radiation damping at the upstream boundary has been included, but bottom absorption has not. The excitation is provided by means of a combisweep which is fashioned so that its continuously varying frequencies pass through the fundamental frequencies of both the arch dam‐reservoir system and the reservoir alone. Consequently the response is highly resonant, thus providing a severe test for the numerical procedures. From the numerical results obtained for an example problem it is concluded that both schemes provide an acceptable solution to the problem posed, and the possibility of enhancement to cater for more complex situations is discussed.
Draft eurocode 8—sample seismic force calculations for discussion purposes
Authors: Hayhurst C. J. , Maguire J. R. 
Published: March 2007

AbstractDraft Eurocode 8 (Common Unified Rules for Structures in Seismic Regions1) is open for study and comment until the latter part of 1989. This paper presents sample seismic force calculations for an idealized building, to illustrate the differing forces which result from the alternative calculation methods allowed. It is tentatively suggested that part of the Draft be revised as a result of the above.
Calculation of foundation uplift effects using a numerical laplace transform
Authors: Hillmer P. , Schmid G. 
Published: March 2007

AbstractA Laplace domain technique to calculate non‐linear foundation uplift effects is presented. Analysis in the Laplace domain permits the modelling of the building structure more precisely by using continuous mass models. Different damping models for every single finite element of the sturcture can easily be utilized via the correspondence principle. Moreover, it is possible to use the substructure method, which permits the modelling of the soil and the building structure separately by different methods. Using, e.g. the boundary element method for the soil, the damping mechanism caused by waves travelling away from the foundation (geometric damping effects) is implicitly included. The model can be condensed to the relevant degrees of freedom of the structure. Two illustrative numerical examples demonstrate the applicability of the method presented.
Wave scattering by a canyon of arbitrary shape in a layered half‐space
Authors: Vogt Rudolf F. , Wolf John P. , Bachmann Hugo 
Published: March 2007

AbstractTo calculate the generalized scattered motion in the region of a canyon of arbitrary shape in a horizontally layered half‐space, the indirect‐boundary‐element method in the frequency domain is applied. Fictitious distributed source loads acting on the line which will form the surface of the canyon are used. The corresponding Green's functions, which are determined by a transformation to the wave‐number domain, satisfy the conditions at the interfaces of the adjacent layers including those at the free surface. The discretization with boundary elements can thus be restricted to the line which will form the surface of the canyon. By formulating a weighted residual statement, the sum of the surface tractions composed of those of the free field and of the fictitious loads averaged over each boundary element are set equal to zero.Based on vast parametric studies addressing inclined body waves and surface waves for the out‐of‐plane and in‐plane cases, the amplification patterns within and adjacent to the canyon are studied and conclusions are stated.
Spline approximations for direct integration of structural dynamics
Authors: Liao Ching‐Lung , Wang Hung‐Chih 
Published: March 2007

AbstractThe application of spline functions in the analysis of structural dynamics is presented in this paper. The nodal points in time discretization for determining the spline curve can be separated into two classes: the p nodal points before the current time (including current time) and the q nodal points after the current time. On the p nodal points, the structural responses were calculated at previous time steps. The q nodal points represent the unknown structural response at future time steps which should meet the requirement of dynamic equilibrium. By a trial and error procedure, at least 16 families of spline curves with different locations of p and q nodal points can be found to meet the requirements of unconditional stability. The accuracy of each family is dependent on the order of the spline and the locations of the nodal points. The 16 families of spline curves supply a wide range of accuracy that can be selected easily. It can be shown that the well‐known Wilson‐method and the Houbolt method are special cases of the present spline approximations.
A simple dynamic substructure method
Authors: Leung A. Y. T. 
Published: March 2007

AbstractThe dynamic substructure method in harmonic vibration is reformulated. A method to accelerate the convergence of D−1 with respect to the number of fixed interface modes is introduced. Comparison is made with the methods of Guyan and Irons, Ritz vector, substructure synthesis and dynamic substructure. A close relation among the methods is examined. The present method can predict more global modes than the number of degrees of freedom retained. It is the most economical in operation counts among the methods for systems having many identical substructures.
Seismic response of structures supported on R‐FBI system
Authors: Mostaghel N. , Khodaverdian M. 
Published: March 2007

AbstractAseismic base isolation is increasingly being utilized to protect structures and their contents against earthquakes. The R‐FBI (Resilient‐Friction Base Isolator) bearings provide a new isolation system. The equations of motions of elastic plane structures supported on R‐FBI bearings and a procedure for their solutions are presented. The responses of a five‐storey 1/3‐scaled frame model to both horizontal components and horizontal and vertical components of six different ground motion records for fixed base and isolated base are evaluated. To estimate the prototype response, the ground motion records are time scaled by The effects of initial base displacement and non‐symmetric friction caused by small differential settlements are also considered. It is concluded that R‐FBI reduces the acceleration response considerably without inducing large base displacements or leaving large residual displacements.
Seismic stability of concrete gravity dams
Authors: Léger P. , Katsouli M. 
Published: April 2007

AbstractLinear finite element analyses are commonly used to simulate the behaviour of gravity dam—foundation systems. However, the foundation is generally unable to develop any significant tensile stresses. Therefore any tension occurring in the vicinity of the dam—foundation interface is largely fictitious. Moreover, the traditional overturning and sliding stability criteria have little meaning in the context of the oscillatory response of dams during earthquakes.In this study, time domain analyses using non‐linear contact elements located at the dam—foundation interface have been used to determine the dynamic sliding and uplifting response of gravity dam monoliths considering various elastic foundation properties. The magnitudes of the relative interface displacements, of the percentage of base not in contact (PBNC) and of the compressive stresses at the heel or toe of the dam have been used to monitor the seismic stability.The numerical results have shown that the non‐linear behaviour of the dam—foundation interface reduces the seismic response of the system, indicating the possibility of more rational and economical designs. The PBNC was identified as the critical seismic stability response parameter for all analyses except for very flexible foundation conditions where the maximum values of relative interface displacements need to be considered.
Bracketed and normalized durations of earthquake ground acceleration
Authors: Kawashima Kazuhiko , Aizawa Koh 
Published: April 2007

AbstractMultiple regression analyses of the duration of earthquake ground acceleration are presented. Two types of duration are considered, i.e. bracketed duration and normalized duration. The bracketed duration ta is defined as the elapsed time between the first and last acceleration excursions greater than a [cm/s2], and the normalized duration Tα is defined as the elapsed time between the first and last acceleration excursions greater than α times (0 < α < 1) the peak acceleration. Employed are 394 components of horizontal strong motion acceleration records obtained at 67 free field sites in Japan. With the use of multiple regression analysis, the dependence of the bracketed and normalized durations on earthquake magnitude and epicentral distance is studied.
Dynamic response of axisymmetric embedded foundations
Authors: Emperador J. M. , Dominguez J. 
Published: April 2007

AbstractThe boundary element method is used to obtain dynamic stiffness functions of rigid cylindrical foundations embedded in a uniform or layered viscoelastic half‐space. Dynamic stiffness functions of hemispherical foundations embedded in a uniform half‐space are also computed. The direct integral equation formulation is used in combination with the complete space point load fundamental solution that is integrated numerically along the azimuthal coordinate. The approach is easy to implement because of the simplicity of the fundamental solution. The numerical results obtained by this method for cylindrical and hemispherical foundations are very close to corresponding published results obtained by different procedures. A parametric study shows the important effects of the Poisson's ratio on the dynamic stiffness functions of cylindrical foundations embedded in a uniform viscoelastic half‐space. The effect of the bedrock compliance on the stiffness functions is also shown in the case of cylindrical foundations embedded in a soil layer that rests on a bedrock.
Additional seismic inelastic deformation caused by structural asymmetry
Authors: Tso W. K. , Ying Hongshan 
Published: April 2007

AbstractUsing a single mass monosymmetric model, this paper examines the additional seismic inelastic deformations and displacement caused by structural asymmetry of the model. Stiffness eccentricity and resistance eccentricity are used as measures of asymmetry in the elastic and inelastic range respectively. Seven ways of specifying strength distribution among resisting elements are considered, including code provisions from Canada, Mexico, New Zealand and the United States. These specifications are related t o the model resistance eccentricity.It is shown that when torsional shears are included in the strength design of the elements, the structure in general will have small resistance eccentricity, even if it has large stiffness eccentricity in the elastic range. For structures which are designed with allowance for torsional shears, the ductility demands on the elements are similar to those when the structure is symmetrical. However, the edge displacements can be up to three times that if the system is symmetrical. This finding has significant implications in evaluating adequate separation between buildings to avoid the pounding problem during earthquakes.