bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotational components of surface strong ground motion
Authors: Oliveira Carlos S. , Bolt Bruce A. 
Published: April 2007

AbstractRotational components of seismic waves have been estimated using the strong motion array in Taiwan, SMART‐1. The inner rings of accelerographs, covering an approximately circular area of 3 km2, permit a decomposition of travelling waves with wavelengths in the range 0.5 to 5.0 km and frequencies from 0.1 to 5 Hz.Rotational components of the strain field, obtained from station pairs and averaged over the array using stacking techniques, were computed for five different earthquakes with Ms magnitude 5.7 to 7.8, and epicentral distances 6 to 84 km. The results indicate peak rotation values about a vertical axis on the order of 4 × 10−5 rad at an approximately 2.5 s period. The measured values for pure rotation and rocking are in agreement with the spatial coherency structure observed in these earthquakes. For comparison, significant effects to engineered structures generally appear when curl u > 10−4 rad. The estimates are important for design of scaled engineered models for soil‐structure interaction experiments.
Water pressures on rigid gravity dams with finite reservoir during earthquakes
Authors: Aviles Javier , Sanchez‐Sesma Francisco J. 
Published: April 2007

AbstractAn approximate analytical solution is presented for earthquake‐induced hydrodynamic pressures on rigid gravity dams with a finite reservoir and incompressible fluid. Using the Trefftz‐Mikhlin method, the solution is constructed with function expansions of solutions of the problem's governing equation which satisfy boundary conditions at the bottom and free surface. Unknown coefficients of the linear combinations are obtained from a continuous least‐squares treatment of the remaining boundary conditions at the upstream dam face and reservoir wall. Numerical results are presented for different geometries of the dam‐water and wall‐water interfaces. Out‐of‐phase motion at the end of the reservoir is considered. When the upstream dam face and reservoir wall are vertical, the known solution for in‐phase dam and wall movement is recovered.
A generalized least‐squares family of algorithms for transient dynamic analysis
Authors: Kujawski Jerzy , Gallagher Richard H. 
Published: April 2007

AbstractBy use of the generalized least‐squares procedure, in conjunction with a finite element approximation in time, a simple three‐time‐level family of time integration schemes is derived. This results in fourth‐order accurate unconditionally stable algorithms and stable eighth‐order accurate non‐dissipative algorithms. Numerical examples show the accuracy of the proposed schemes in comparison with the Fox‐Goodwin formula and Newmark's average acceleration method.
Seismic response of the superstructure and attached equipment in a base‐isolated building
Authors: Tsai Hsiang‐Chuan , Kelly James M. 
Published: April 2007

AbstractBase isolation can be used both to protect the structure and simultaneously to reduce the response of internal equipment. The seismic response of a base‐isolated structure has been studied through the shaking table test or numerical calculation before. The object of this paper is to analyse a base‐isolated structure by a different analytical approach—perturbation analysis.Recognizing that the horizontal stiffness of an isolation system is much smaller than that of the superstructure, the mathematical expressions of the modal properties of base‐isolated structures are derived by the perturbation method in terms of the modal properties of the superstructure and used to study the dynamic response of superstructure and attached equipment in the base‐isolated building.This study shows that the first base‐isolated mode not only controls the superstructural response but also dominates the response of high‐frequency attachment. The contribution of higher modes to the response of base‐isolated structures, which is proportional to the horizontal stiffness of isolation system, is very small.
Formulae for errors for initial displacement and velocity problems using the Newmark method
Authors: Warburton G. B. 
Published: April 2007

AbstractA standard test of the Newmark method in structural dynamics is its application to the determination of the response of a damped or undamped single‐degree‐of‐freedom system to a prescribed initial displacement or velocity. In this paper formulae for the error, Δj, in the response, after applying the Newmark method for j time‐steps each of duration Δt, are proposed and their acceptable accuracy is demonstrated.
Effects of concrete cracking on the earthquake response of gravity dams
Authors: Vargas‐Loli Luis M. , Fenves Gregory L. 
Published: April 2007

AbstractTensile stresses exceeding the tensile strength of concrete can develop in concrete dams subjected to earthquake ground motion. This study examines the earthquake response of gravity dams including tensile cracking of the concrete. The interaction between the dam and compressible water is included in the analysis using a numerical procedure for computing the non‐linear dynamic response of fluid‐structure systems. The crack band theory is used to model tensile cracking with modifications to allow for the large finite elements necessary for dam analysis. The earthquake response of a typical gravity dam monolith shows that concrete cracking is an important non‐linear phenomenon. Cracking is concentrated near the base of the dam and near the discontinuities in the face slope. The extensive cracking, which develops due to ground motion typical of maximum credible earthquakes, may affect the stability of dams during and after strong earthquakes.
Soil‐pile‐structure interaction effects on the seismic response of a cooling tower
Authors: Ahn Kijun , Gould Phillip L. 
Published: April 2007

AbstractA study of the effects of soil‐pile‐structure interaction on the response of rotational shell structures supported by a group of vertical piles is presented. The interaction effects are included in the dynamic analysis through the development of a frequency dependent boundary system at the interface between the shell and the underlying foundation. The substructure method is used to simplify the connection problem between the shell and the pile foundation. A free vibration analysis of a cooling tower is carried out to investigate the dynamic properties of rotational shells with four different foundation stiffnesses. The effects of soil‐pile‐structure interaction on the response in the shell are demonstrated by a complex response analysis of a cooling tower.
Attenuation of seismic intensity in Albania and Yugoslavia
Authors: Trifunac M. D. , Todorovska M. I. 
Published: April 2007

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 Shebalin et al.19 The 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 Yugoslavia.
Modal identification of self‐adjoint distributed‐parameter systems
Authors: Norris Mark A. , Silverberg Larry 
Published: April 2007

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 domain method.
An improved implicit‐explicit time integration method for structural dynamics
Authors: Miranda Isidoro , Ferencz Robert M. , Hughes Thomas J. R. 
Published: April 2007

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 dynamics calculations.
Response analysis of hysteretic multi‐storey frames under earthquake excitation
Authors: Nielsen S. R. K. , Mørk K. J. , Thoft‐Christensen P. 
Published: April 2007

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 order n ≧ 1, where n = 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 linearization.
Analytic solutions for soil‐structure interaction in layered media
Authors: Liou Gin‐Show 
Published: April 2007

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 presented.
The dynamics of interstructural connection to prevent pounding
Authors: Westermo Bruce D. 
Published: April 2007

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.
Seismic responses of deck‐type arch bridges
Authors: Dusseau Ralph A. , Wen Robert K. 
Published: April 2007

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, 0.22g and 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 substantial.
Symmetrical fft technique and its applications to earthquake engineering
Authors: Katukura Hiroshi , Ohno Susumu , Izumi Masanori 
Published: April 2007

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 framework.
Soil‐structure interaction experiment using impulse response
Authors: Mita A. , Yoshida K. , Kumagai S. , Shioya K. 
Published: April 2007

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 tools.
A study of seismic response characteristics of structures with friction damping
Authors: Malushte S. R. , Singh M. P. 
Published: April 2007

AbstractThe effectiveness of introducing Coulomb damping in structures to reduce seismic response is evaluated. Response characteristics of simple one‐degree‐of‐freedom structures with sliding interfaces between the top slab and supporting frame and between the base and foundation are studied and compared. It is shown that, analytically, the top slab sliding system is a special case of the base sliding system. The slab sliding system is seen to offer certain advantages over the base sliding system inasmuch as it provides a more effective reduction in the lateral forces in the supporting frame as well as a better isolation of supported secondary systems, as depicted by a significantly reduced level of floor spectrum response. The analytical ease of predicting the response of the slab sliding system is also demonstrated. The required unobstructed sliding displacements seem to be reasonable except, may be, for flexible systems. The similarities and differences between the hysteretic and slab sliding systems are also highlighted by comparison of their response results.
On the rotational components of seismic motion
Authors: Castellani A. , Boffi G. 
Published: April 2007

AbstractThe surface motion during an earthquake is different from point to point depending on the propagation properties of the seismic waves. Rocking and torsion are thus present in the free field, in proportion to the spatial derivatives of the surface motion with respect to a given direction. These derivatives are inversely proportional to the apparent wave velocity in that direction, so the smaller the wave apparent velocity, the more important its contribution to the rotations. In this respect, a marked contribution to surface rotations from surface waves is expected.A mathematical model is presented, based on a detailed representation of soil impedance, an approximate identification of surface waves and a deconvolution of body waves in P and SV contributions. Through this model the surface motion obtained from the records of strong‐motion accelerometers can be expressed as a superposition of plane waves of known wavelengths.Rocking response spectra are computed and results are compared with previously published spectra. A sensitivity analysis is performed on some parameters of the model.
Influence of lateral‐load‐resisting system on the earthquake response of structures—a system identification study
Authors: Papageorgiou Apostolos S. , Lin Bing‐Chang 
Published: April 2007

AbstractAnalysis and comparison of the dynamic responses of three well instrumented (with accelerographs) high‐rise buildings shaken during the 1984 Morgan Hill earthquake are presented. The buildings examined in the present work are (i) the Town Park Towers Apartment building, a 10‐storey, concrete shear wall building; (ii) the Great Western Savings and Loan building, a 10‐storey building with concrete frames and shear walls; and (iii) the Santa Clara County Office building, a 13‐storey, moment‐resistant steel frame building. The structures are located within 2 km of each other and, as may be confirmed by visual inspection of the recorded seismograms, experienced similar ground motions. One‐dimensional and three‐dimensional linear structural models are fitted to the observations using the modal minimization method' for structural identification, in order to determine optimal estimates of the parameters of the dominant modes of the buildings. The time‐varying character of these parameters over the duration of the response is also investigated. Comparison of the recorded earthquake response of the structures reveals that the type of lateral‐load‐resisting system has an important effect on the dynamic behaviour of the structures because it controls the spacing of the characteristic modes on the frequency axis. The Santa Clara County Office building has closely spaced natural frequencies and exhibits strong torsional response and modal coupling. Its dynamic behaviour is contrasted with that of the Great Western Savings and Loan building which has well separated natural frequencies and exhibits small torsional response and no modal coupling. Strong modal coupling causes a beating‐type phenomenon and makes earthquake response of structures different from that envisioned by codes.
Full‐scale dynamic testing of the Alamillo cable‐stayed bridge in Sevilla (Spain)
Authors: Casas Juan R. 
Published: April 2007

AbstractAccelerations and displacements due to dynamic excitation by simulated traffic consisting of two trucks, were measured on the deck and tower of the Alamillo cable‐stayed bridge. Also the dynamic testing program included the measurement with accelerometers of the free‐damped vibration of the 26 cables achieved by means of quick‐releasing force. From these measurements it was possible to obtain the dynamic parameters of the bridge (natural frequencies and damping ratios) and the real forces in the cables. In the paper, only the tests, results and conclusions related to dynamic parameters of the bridge are presented. The objective of the dynamic tests herein described was to validate the mathematical modelling and the wind‐tunnel models used in the dynamic analysis of the bridge in front of traffic and wind‐forces. As the agreement between dynamic parameters of the real bridge and theoretical and scaled models was very satisfactory, the correct dynamic behaviour of the bridge in response to traffic and wind (vortex shedding, flutter, etc.) can be deduced jointly with the correct alignment and expected internal forces in the permanent state in tower and deck.
Effective strength eccentricity concept for inelastic analysis of asymmetric structures
Authors: Mittal A. K. , Jain Ashok K. 
Published: April 2007

AbstractA large number of parameters affect the inelastic response of an eccentric system. The centre of resistance no longer remains constant due to continuous loading and unloading of various elements of the system in and out of the inelastic region. The objective of this study is to develop the concept of strength eccentricity for asymmetrical structures excited well into the inelastic region in the event of a severe earthquake. A single mass monosymmetric three‐element system is selected. The torsional flexibility parameter is varied so as to obtain nine eccentric configurations covering the entire spectrum of such systems. These models were subjected to S00E component of the El Centro earthquake of 1940 which is considered to be a very severe earthquake. The concept of effective strength eccentricity is introduced which is defined as strength eccentricity at the point of intersection of ductility ratio curves of REE and FEE. It is proposed to provide additional strength in the elements of a torsionally unbalanced system independent of the design eccentricity. Empirical equations are proposed to account for design eccentricity and additional strength as well as distribution of the design strength. The proposed formulation is compared with the torsional provisions of UBC 1991, NBCC 1990 and NZC 1992. It is concluded that additional ductility demand on the REE and FEE designed based on the proposed formulation is almost nil as compared to that given by the three codes. The NZC and UBC require maximum ductility on the REE. The increase in overall strength of the system is least for the proposed formulation as compared to that given by the three codes. NBCC consistently requires the maximum total strength ratio.