bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distance scaling of vertical and horizontal response spectra of the Loma Prieta earthquake
Authors: Bozorgnia Yousef , Niazi Mansour 
Published: April 2007

AbstractAttenuations of the vertical and horizontal response spectra of the 17 October 1989 Loma Prieta, California, earthquake are developed through analyses of the ground motion at 53 sites within a 100 km radius of the source. The analyses are performed on the spectral ordinates for 16 incremental periods ranging from 0.05 to 2.0 sec. The response spectra are modelled empirically for two different site conditions characterized by rock and stiff‐soil geologies. Data analysis is performed by the application of a non‐linear multivariate regression procedure allowing for distance and site factor as independent variables. Variation of the vertical‐to‐horizontal (V/H) spectral ratios with wave frequency and distance shows the same behaviour as observed previously in the widely separated geographic regions of northeastern Taiwan and east‐central Iran. The predicted ratios at sites underlain by stiff soil are generally higher than the commonly used value of 2/3 at high frequencies ( > 5 Hz) in the near‐source region (R < 30 km), but reduce to 1/2 or less at longer periods and farther distances. This behaviour is also observed at rock sites; however, it is somewhat less pronounced.With a faster attenuation of spectral ordinates at higher frequencies, the shape of the response spectrum is found to change with distance. As expected, the spectral attenuation with distance is generally higher for the vertical spectrum than for the horizontal spectrum. The difference is particularly significant at the higher‐frequency end of spectrum.Site amplification factors for stiff soil with respect to rock geology varies between 1.17 and 1.72 for horizontal spectrum and 1.01 and 1.81 for vertical spectrum. Spectral amplifications at four sites underlain by soft soil and artificial fill, are also evaluated. This is done by a comparison of the observed spectra with those predicted for rock geology at corresponding distances. As expected, the resulting amplification factors at soft‐soil sites show significant increase relative to those at sites underlain by rock.
Seismic displacements on shear surfaces in cohesive soils
Authors: Tika‐Vassilikos Theodora E. , Sarma Sarada K. , Ambraseys Nicholas N. 
Published: April 2007

AbstractThe paper is concerned with the earthquake‐induced displacements on pre‐existing shear surfaces in cohesive soils. Results from ring shear tests have shown that during fast shearing the strength of such surfaces depends on displacement and rate of shearing. The test results have been used in a numerical analysis to assess the displacement of a rigid block sliding on a plane surface. The results from the analysis show that the earthquake‐induced displacements on pre‐existing shear surfaces are influenced significantly by the soil behaviour under earthquake loading conditions. The results are consistent with the field performance of pre‐existing slides in cohesive soils during earthquakes.
Boundary integral equation method for the diffraction of elastic waves using simplified green's functions
Authors: Chang Wei‐Lung 
Published: April 2007

AbstractAn alternate formulation of the ‘substructure deletion method’ suggested by Dasgupta in 19791 has been successfully implemented. The idea is to utilize simple Green's functions developed for a surface problem to replace the more complicated Green's functions required for embedded problems while still being able to generate an accurate solution. Since the exterior medium is usually represented by a continuum model, the interior medium in the present approach will also be represented by a continuum model rather than a finite element model as suggested originally, thereby eliminating the incompatibility between the solutions of the interior and exterior media. Detailed studies of the method's accuracy and limitations were performed using two‐dimensional examples in wave scattering of canyons and alluvial valleys, problems which are more suitable for this method than the embedded foundation problem. The results obtained indicate that the alternate formulation gives accurate results only when the vertical dimension of the scattering object is not too large; if the aspect ratio (vertical over lateral) exceeds a certain limit, the results will not approach the known results given by boundary integral equation solutions or indirect boundary integral equations no matter what the refinement of the model may be. The greatest advantage of the present method is that the task of calculating Green's functions is reduced significantly; computational time using this new formulation is approximately five times less than for conventional boundary integral equation methods.
Sloshing response of layered liquids in rigid tanks
Authors: Veletsos A. S. , Shivakumar P. 
Published: April 2007

AbstractThe sloshing action of layered liquids in rigid cylindrical and long rectangular tanks is investigated, considering both their free vibrational characteristics and their response to a horizontal component of base shaking. Special attention is given to the maximum surface displacement induced by the base motion. The analysis is formulated for systems with N superimposed layers of different thicknesses and densities, and is illustrated by a numerical example. In addition, comprehensive numerical data are presented for two‐layered and some three‐layered systems which elucidate the underlying response mechanisms and the effects and relative importance of the numerous parameters involved. It is shown that for each horizontal natural mode of vibration, there are N distinct vertical modes, the frequencies of which are lower than the natural frequency of a homogeneous liquid of the same total depth. It is further shown that the maximum surface sloshing displacement of the base‐excited layered system is typically larger than that of the corresponding homogeneous system, and that the results for the long rectangular and cylindrical tanks are quite similar.
A readily available energy source for active vibration control in buildings
Authors: Utku Senol , Utku Bisulay , Wada Ben K. 
Published: April 2007

AbstractBy equipping structures with appropriate actuators, sensors and microprocessors, it is possible to suppress actively the undesirable vibrations of the structures. Due to small energy requirements, the vibration suppression in large space trusses orbiting the Earth by controlling the elongations and contractions of length‐adjustable bars of the truss has been shown to be feasible both theoretically and experimentally. This method of vibration suppression is part of the ‘adaptive structures technology’. It can be used for suppressing the vibrations of a building subjected to earthquake or wind excitations, provided that the much higher energy and power requirements are met. In this work the use of gravitational energy of the mass of the building is proposed for active vibration control.
The use of damage functionals in earthquake engineering: A comparison between different methods
Authors: Cosenza Edoardo , Manfredi Gaetano , Ramasco Roberto 
Published: April 2007

AbstractThe behaviour of the EPP‐SDOF model under seismic actions is analysed herein by different ‘damage functionals’ to define collapse under cyclic loading. In particular, the damage functionals based on the concept of maximum ductility and dissipated plastic energy are first compared. Afterwards the methods of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue are reviewed and extensively analysed. Comparisons in the case of simple cyclic histories and in terms of acceleration collapse spectra are carried out with reference to significant earthquake records. In particular, it is shown in which cases the damage functionals of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue, completely defined by the value of a single parameter, degenerate in the limit methods of ductility or dissipated energy and in which cases they provide similar results.
Prediction of the spatial distribution of the modified mercalli intensity using neural networks
Authors: Tung Albert T. Y. , Wong Felix S. , Dong Weimin 
Published: April 2007

AbstractThis paper presents the development of an adaptive, non‐parametric forecast model for the direct prediction of the spatial distribution of the Modified Mercalli Intensity (MMI) corresponding to an earthquake scenario. The model is based on recent advances in neural networks computation, and is constructed through supervised learning using historical earthquake and regional geological data as training sets. A MMI forecast model for moderate earthquakes with magnitudes between 6 and 7 was developed based on data from the Loma Prieta, Coalinga and Morgan Hill earthquakes. For these data sets, the neural networks forecast model is shown to have excellent data synthesis capability; multiple sets of data can be encapsulated by a relatively simple network architecture. Limited comparison of forecasts made by the neural networks model and conventional models demonstrates that improved accuracy can be achieved. Implementation and operational advantages of the neural networks approach such as general input features, minimum preconceived knowledge of the data sets, the ability to learn and to adapt incrementally and the autonomous and automatic synthesis of the structure underlying the data sets, have been illustrated.
Insight on 2D‐ versus 3D‐modelling of surface foundations via strength‐of‐materials solutions for soil dynamics
Authors: Wolf John P. , Meek Jethro W. 
Published: April 2007

AbstractTo simplify the analysis, three‐dimensional soil–structure interaction problems are often modelled by considering a two‐dimensional slice without changing the material properties of the soil. This procedure, although convenient, is of questionable validity because two‐dimensional modelling inherently overestimates the radiation damping for translational and rocking motions. To make matters worse, two‐dimensional modelling always entails an underestimation of the dynamic‐spring coefficient for the translational motions. The damping ratio of the two‐dimensional case, which is proportional to the ratio of the damping coefficient to the spring coefficient, will thus be even larger. Thus, reliance upon a two‐dimensional analysis based on an equivalent slice of a strip foundation may result in a dangerously non‐conservative design.Valuable insights into the essence of radiation damping and the difference between two‐dimensional and three‐dimensional models may be obtained via approximate strength‐of‐materials solutions based on cone–wedge models and travel‐time considerations. By examining the decay of the waves along the axes of the cone–wedge models, the essence of radiation damping can be grasped. The heuristic concept of more spreading of waves in three dimensions than in two is misleading. Indeed, just the opposite is true: The less the amplitude spreads and diminishes with distance, the greater is the radiation damping.Because the damping ratio is grossly overestimated, two‐dimensional modelling of a three‐dimensional case cannot be recommended for actual engineering applications. It is more feasible to take the opposite approach and idealize slender soil–structure interaction problems with a radially symmetric model.As an alternative, when defining the equivalent slice of the two‐dimensional strip foundation, the impedance of the soil can be changed to achieve a much better agreement of the high‐frequency limits of the damping coefficients. In the low‐frequency range this modified two‐dimensional model also overestimates radiation damping, although to a lesser extent.As a by‐product, the dimensions of the equivalent slice of a two‐dimensional strip foundation are discussed; and equations for the aspect ratios determining the opening angles of the corresponding wedges are derived. Also addressed is the quite separate but related topic of the transition from square to slender rectangular foundations.
The imaginary counterpart of recorded motions
Authors: Makris Nicos 
Published: April 2007

AbstractIn this paper it is shown that any recorded motion has an imaginary counterpart. Starting from the harmonic input motion where the sine function is the imaginary counterpart of the cosine function, it is shown that all time histories exist in pairs. The imaginary counterpart of records is not needed when the response of a system is described by a real‐parameter constitutive model. However, it is shown that when complex‐parameter models are used, the imaginary counterpart of records has equal importance as the real‐valued record and in this case the input motion should be strictly complex valued. The procedure to construct the imaginary counterpart of any piecewise continuous record is developed. A constructed complex‐valued earthquake time history is used as input motion to a system described by a Kelvin model with complex damping constant. The validity of the procedure is demonstrated by comparing the response of the complex‐damping Kelvin model against the results obtained from a mathematically equivalent real‐valued formulation.
On non‐linear dynamic analysis in the frequency domain: Algorithms and applications
Authors: Aprile A. , Benedetti A. , Trombetti T. 
Published: April 2007

AbstractIt is well known that the solution of the forced vibration of a N‐DOF dynamical problem is very cumbersome when conditions which allow the equations to uncouple do not exist. In the literature several techniques were proposed to overcome the problem, but they were mainly focused on a particular problem in turn. So, we deemed it useful to search for a unifying procedure able to deal with different sources of non‐linear behaviour introducing only minor changes in the operation flow.In this respect, attention is paid to the Alternating Frequency/Time domain method (AFT) which draws its robustness from the speed and switching capabilities of the Fast Fourier Transform; moreover, taking advantage of the pseudo‐force concept, we can arrive at a solution method featuring greater generality and able to solve different non‐linear dynamical problems by means of specialization of the same conceptual framework (G‐AFT or Generalized AFT).In the first section of the paper the theoretical background is discussed in detail and the proposed algorithms are presented. In the second one, several examples of technical relevance are documented and solved, highlighting the efficiency, convergence and accuracy of the presented algorithm.For cases such as an 11‐storey building or a block simulated power plant we introduce the soil‐structure interaction effect by means of non‐proportional damping; the responses computed either by direct frequency analysis or by iteration are compared with existing solutions or with time domain solutions determined through the Newmark β method.An original example prepared by the authors and fully referenced is finally worked out in order to show the capability of the method when Coulomb damping is taken into account; this effect covers a significant practical relevance in the base isolation field.
Identification of modal quantities from two earthquake responses
Authors: Benedetti D. , Gentile C. 
Published: April 2007

AbstractThe work deals with the identification of modal parameters of a structure from earthquake records when the input ground motion is unknown. This may occur, for example, owing to instrumental malfunctions.The procedure is based on the assumption that at least two responses are available and consists of two main steps. In the first one, modal frequencies are estimated by searching relative minima of a function that involves the ratio of the Fourier amplitudes of the two records, while the second phase is devoted to the identification of other modal quantities (i.e. effective participation factors and modal dampings).Once the identification process has been completed, an estimate of the unknown base input may be performed by means of the IFFT algorithm. The proposed approach has been checked against both finite element simulations of simple structures and field measurements on real buildings.
Robust control techniques for buildings under earthquake excitation
Authors: Schmitendorf W. E. , Jabbari Faryar , Yang J. N. 
Published: April 2007

AbstractRobust control techniques are applied to civil engineering structures subjected to earthquake excitation. Full‐state feedback and observer‐based control laws are used to reduce the response of the building due to earthquake ground motion. Effects of actuator dynamics and a method to incorporate these dynamics into the overall design are also presented. The effectiveness of the control method is demonstrated by simulation results.
Seismic response of a cylindrical shell embedded in a layered viscoelastic half‐space. II: Validation and numerical results
Authors: de Barros F. C. P. , Luco J. E. 
Published: April 2007

AbstractA procedure to calculate the three‐dimensional harmonic response of a infinitely long cylindrical shell of circular cross‐section embedded in a layered viscoelastic half‐space and subjected to harmonic plane waves impinging at an oblique angle with respect to the axis of the shell is validated by extensive comparisons with previous two‐ and three‐dimensional results for the particular case of a shell embedded in a uniform half‐space. New numerical results describing the motion and stresses within a shell embedded in a multilayered half‐space and subjected to obliquely incident P‐, SV‐ and SH‐waves with different horizontal angles of incidence are presented and discussed.
Magnitude–intensity and intensity–attenuation relationships for atlas region and Algerian earthquakes
Authors: Benouar D. 
Published: April 2007

AbstractThis paper presents the results of an investigation of the magnitude–intensity and intensity–attenuation relationships for earthquakes in the Atlas block and Algeria using macroseismic data. This work is based on a selected sample of isoseismal maps from 32 events which were recently revised. Surface‐wave magnitudes, Ms, are recalculated using the Prague formula and range from 4·2 to 7·45. Because the Atlas mountains block is in a collision zone, earthquakes occur in general within a layer 15 km deep. Expressions of general form for the magnitude–intensity and intensity–attenuation correlations are adopted and are, respectively,

and

where R2 = d2 + h2, d the source distance in km, h the focal depth in km, Ms the revised surface‐wave magnitude, Msc the predicted surface‐wave magnitude, Ii the intensity at isoseismal i, I the predicted intensity, σ the standard deviation and P is zero for 50‐percentile values and one for 84‐percentile, and the coefficients A's and B's are determined by regression analysis. The results of this study show that the intensity–attenuation models are adequate to predict quite well the die‐out of intensity with distance in the Atlas zone and coastal Algeria; it is also found that magnitude can be predicted accurately by calibrating isoseismal radii against revised instrumental surface‐wave magnitude. Such magnitude–intensity relationships may be used to evaluate the magnitude of historical earthquakes in the region under survey, with no instrumental data, for which isoseismal radii and intensities are available.
Accidental torsion in buildings due to base rotational excitation
Authors: de la Llera Juan C. , Chopra Anil K. 
Published: April 2007

AbstractThis investigation is concerned with accidental torsion in buildings resulting from rotational excitation (about a vertical axis) of the building foundations as a result of spatially non‐uniform ground motions. Because of this accidental torsion, the displacements and deformations in the structural elements of the building are likely to increase. This increase in response is evaluated using actual base rotational excitations derived from ground motions recorded at the base of 30 buildings during recent California earthquakes. Accidental torsion has the effect of increasing the building displacements, in the mean, by less than 5 per cent for systems that are torsionally stiff or have lateral vibration periods longer than half a second. On the other hand, short period (less than half a second) and torsionally flexible systems may experience significant increases in response due to accidental torsion. Since the dependence between this increase in response and the system parameters is complex, two simplified methods are developed for conveniently estimating this effect of accidental torsion. They are the ‘accidental eccentricity’ and the ‘response spectrum’ method. The computed accidental eccentricities are much smaller than the typical code values, 0.05bb or 0.1b, except for buildings with very long plan dimensions (b ≥ 50 m). Alternatively, by using the response spectrum method the increase in response can be estimated by computing the peak response to each base motion independently and combining the peak values using the SRSS rule.
Dynamic stiffness of foundation on layered soil half‐space using cone frustums
Authors: Wolf John P. , Meek Jethro W. 
Published: April 2007

AbstractApproximate dynamic‐stiffness coefficients of a disk on the surface of a single layer on a half‐space may be calculated using cone models. This concept is generalized to the case of a horizontally stratified site consisting of many layers on a homogeneous half‐space. After constructing the so‐called ‘backbone cone’ determining the radii of the disks at all interfaces, the dynamic‐stiffness matrices of the layers (modelled as cone frustums) and the dynamic‐stiffness coefficient of the underlying half‐space (modelled as a cone) are assembled to that of the site. The dynamic‐stiffness matrix of a layer is a complex‐valued function of frequency because radiation of energy in the horizontal direction is considered. In this model of the layered half‐space the properties of the cone reproduce themselves (cloning). The advantages of using cone models are also present for the layered half‐space; in particular, no transformation to the wave‐number domain is performed.
An equivalent linear finite element approach for the estimation of pile foundation stiffnesses
Authors: Maragakis E. A. , Douglas B. M. , Abdel‐Ghaffar S. M. 
Published: April 2007

AbstractA method is presented for the calculation of the displacement‐dependent lateral, vertical and rotational stiffnesses of the central pier of the Meloland Road Overcrossing. This method is based on a finite element model of the foundation and an ‘equivalent linear’ iterative procedure for the calculation of the stiffness versus displacement curves. The results of this procedure are then compared to the results of system identification studies based on the full‐scale test measurements of the structure and to the results of studies performed by other researchers. It was found that this method produced reliable strain‐dependent stiffness values.