bluuebunny/crossref_metadata_2025 huggingface dataset:
Envelopes of maximum seismic response for a partially symmetric single storey building model
Authors: Dempsey K. M. , Irvine H. M.
Published: March 2007

An analysis is made of the coupled lateral‐torsional response of a partially symmetric single‐storey building model to horizontal translatory earthquake excitation. Interest centres on the evaluation of realistic estimates for two equivalent static actions (a shear and a torque) which account for the worst dynamic consequences of torsional unbalance. The results substantiate the findings of previous investigations which have given rise to the belief that strong modal coupling and severely coupled lateral and torsional responses are possible even in nominally symmetric buildings. The response of the model is assumed to be linearly elastic and viscously damped.

In a preliminary analysis the equations of motion are solved using the modal analysis technique and the conditions necessary for full modal coupling are ascertained.

Then by employing the design spectrum concept, together with suitably conservative procedures for combining the modal maxima, dimensionless forms of the equivalent static actions are evaluated as functions of two independent parameters. The final results are furnished by modified square root of the sum of the squares (SRSS) combination functions which take account of the spacing between the translational and torsional frequencies. Examples at the end of the paper illustrate the practical significance of the work.
Simulation of three‐dimensional strong ground motions along principal axes, San Fernando earthquake
Authors: Kubo Tetsuo , Penzien Joseph
Published: March 2007

Power spectral density which describes frequency content is considered one of the most significant properties to be taken into account when generating ground motions through the use of stochastic processes. Using a smoothed and normalized Fourier amplitude spectrum, frequency content for components of motion along a set of principal axes is estimated. Fourier amplitude spectra obtained by this moving‐window technique are presented which show the time dependency of frequency content for motions produced by the San Fernando earthquake of 9 February 1971.

A mathematical model to simulate ground motion processes is proposed for which both the intensity and frequency content are non‐stationary. Using this mathematical model with parameter characteristics along principal axes similar to those of the motions recorded during the San Fernando earthquake, three‐dimensional ground motions are synthetically generated. The properties of the simulated motions show general characteristics similar to the characteristics observed in real accelerograms. The suggested model is considered adequate for engineering purposes.
The inelastic vibration absorber subjected to earthquake ground motions
Authors: Jagadish K. S. , Prasad B. K. Raghu , Rao P. Vasudeva
Published: March 2007

Two storey bilinear hysteretic structures have been studied with a view to exploring the possibility of using the dynamic vibration absorber concept in earthquake‐resistant design. The response of the lower storey has been optimized for the Taft 1952, S69°E accelerogram with reference to parameters such as frequency ratio, yield strength ratio and mass ratio. The influence of viscous damping has also been examined.
Response using the Rayleigh‐Ritz method
Authors: Warburton G. B.
Published: March 2007

As an example of the extension of the Rayleigh‐Ritz method to response calculations, analysis is outlined for a damped rectangular plate. For harmonic excitation amplitudes of displacement and bending moment are compared with values from a modal solution from the plate equation. In general, the Rayleigh‐Ritz method predicts displacements of acceptable accuracy, but for a given number of terms accuracy is less for response calculations than for the determination of comparable eigenvalues. Bending moments may converge slowly to the true values, as the number of terms in the assumed series is increased.
Axisymmetric transients in shells of revolution
Authors: Thambiratnam D. P. , Shah A. H. , Cohen H.
Published: March 2007

The propagation of axisymmetric transients in shells of revolution subjected to impulsive boundary loads is treated in this paper. Consideration is restricted to linear, elastic, isotropic, homogeneous shells of revolution with straight line generators. The analysis is based on the concept of a wave as a carrier of discontinuities in the field variable and its derivatives. These discontinuities are determined from a set of recurrence relations which are in turn generated by the use of asymptotic series solutions to the equations of motion. A numerical superposition technique which enables the calculation of long time response is developed. Several numerical examples are presented in order to illustrate the method.
Evaluation of simulated ground motions for predicting elastic response of long period structures and inelastic response of structures
Authors: Chopra Anil K. , Lopez Oscar A.
Published: March 2007

The response of linear elastic and non‐linear hysteretic systems having a single degree of freedom to recorded and simulated ground motions is studied. The objective is to evaluate whether the commonly used simulated motions are appropriate for predicting inelastic response of structures and elastic response of long period structures.

Eight simulated motions were generated to model properties of horizontal ground motions recorded during four earthquakes. The simulated motions are sample functions of a stationary, Gaussian white noise process, multiplied by a temporal intensity function and passed through a linear single‐degree‐of‐freedom filter. Two versions, corresponding to parabolic and ‘standard’ base line corrections (BLC), of each of the simulated and recorded accelerograms were considered.

The following general conclusions are deduced. Simulated ground motions should be subjected to the standard BLC, because it results in more reliable ground velocities and displacements, which in turn would lead to more reliable predictions of response of long period structures. Furthermore, the spectral density of the underlying random process, from which the simulated motions are obtained, should be modified to be more representative of the frequency content of recorded motions, especially in the low frequency range. Such an improved model can be expected to lead to better agreement, over a broad range of periods, in the average response spectra of simulated and recorded motions, for elastic as well as inelastic systems.
On the accuracy of mode superposition analysis in structural dynamics
Authors: Hansteen Ole Edvard , Bell Kolbein
Published: March 2007

It is pointed out that the number of modes which should be included in a mode superposition dynamic response analysis depends on both the frequency content and the distribution of the loading. If the loading frequency is low the effect of the higher modes can be approximated by a static analysis. A technique is described for calculating this static contribution from the higher modes; the total response is then represented by the sum of the lower mode dynamic response and the higher mode static effects. The effectiveness of the procedure is demonstrated by a numerical example.
On the significance of phase content in earthquake ground motions
Authors: Ohsaki Y.
Published: March 2007

A number of problems relating to characteristics of harmonic phase angles contained in earthquake ground motions are discussed, which have been mostly overlooked in the past in contrast with the importance placed on harmonic amplitudes. Particularly, the significance of the concept of phase differences in certain properties of earthquake ground motions is emphasized. A few applications of this new concept to earthquake engineering problems are illustrated as well.
Generation of artificial strong motion accelerograms
Authors: Wong H. L. , Trifunac M. D.
Published: March 2007

A method for generating synthetic strong motion accelerograms for use in engineering design is presented. This method utilizes the model proposed by Trifunac in 197127 in conjunction with the recent empirical scaling functions for characterization of amplitudes and duration of strong shaking in terms of (i) earthquake magnitude, M, and epicentral distance, R, or (ii) Modified Mercalli Intensity (MMI) at the recording station. The method also enables one to consider the desired levels of confidence that the synthetic motion will not be exceeded, direction of ground motion (horizontal or vertical) and the dispersive properties of geologic environment beneath and surrounding the station. The principal features of this approach are that the resulting accelerograms have non‐stationary frequency and amplitude characteristics which are in full agreement with known principles of wave propagation through a stratified medium, and that the Fourier amplitudes and the frequency‐dependent duration are scaled in accordance with known trends as in recorded accelerograms.
Use of fault displacements in the evaluation of seismic risk
Authors: Kaul Maharaj K.
Published: March 2007

The need for a probabilistic description of earthquake magnitudes and their epicentres, specifically their joint probability density function, arises in the quantitative assessment of seismic risk. For line sources, this description has generally been assumed to be of a specific form dictated primarily by the unavailability of relevant statistical data. The need for such simplification can, however, be eliminated if the available statistical data are supplemented by the knowledge of the accumulated displacements on the fault, thereby leading to an improved estimate of the required probability density function. A procedure to obtain such an improved estimate and simultaneously the mean occurrence rate of earthquakes originating from the fault is developed in this paper. The use of these refined inputs in the seismic risk evaluation is described. Numerical examples are presented for illustration.
Dynamic fluid effects in liquid‐filled flexible cylindrical tanks
Authors: Fischer D.
Published: March 2007

The velocity potential of a compressible fluid is found by Galerkin's method. Free surface displacements and a flexible tank wall are assumed. Explicit expressions for the impulsive mass, the impulsive moment and the overturning moment are derived for wave number m = 1. In the case of m ≥ 1 the dynamic effect of the fluid is represented by a fictitious apparent mass in explicit form.
Response of sliding structures to earthquake support motion
Authors: Mostaghel N. , Tanbakuchi J.
Published: March 2007

To study the effectiveness of sliding supports in isolating structures from damaging earthquake ground motions, a mathematical model of a single degree of freedom structure supported on a sliding foundation and subjected to the N‐S component of the El Centro 1940 earthquake is considered. Spectra for absolute accelerations, relative displacements, relative‐to‐ground displacements, sliding displacements and residual sliding displacements are evaluated for three mass ratios, four coefficients of friction and a damping of 5 per cent critical. It is observed that, for structures with periods less than 1‐8 s, for the coefficients of friction considered, the suprema of relative‐to‐ground displacements, sliding displacements and residual sliding displacements are only of the order of 1–25 times the peak ground displacement. To study the response sensitivities, the spectra for absolute acceleration and sliding displacement of the 1949 Olympia earthquake (S86E component) are also presented. It is concluded that sliding supports can be quite effective in isolating structures from support excitations.
Seismic response of torsionally coupled base isolated structures
Authors: Pan Tso‐Chien , Kelly James M.
Published: March 2007

An analytical study of the seismic response of typical base isolated structures mounted on rubber bearings is presented. Isolated buildings are liable to have closely spaced lower modes of vibration with small eccentricity between centres of mass and rigidity. The isolated structure is modelled as a rigid deck with lumped masses supported on axially inextensible elastomeric rubber bearings. This simplified system has three degrees of freedom (dof), two translations and one rotation in the horizontal plane.

The Green's functions for the displacement response of the 3 dof system are derived for both undamped and damped cases with small and large eccentricities. The small eccentricity case is taken from a specific isolated building, while the large eccentricity case arises from the 5 per cent accidental eccentricity which is required by various seismic codes.

An interaction equation for normalized displacements is established for an idealized flat velocity spectrum or hyperbolic acceleration spectrum. An isolated building on rubber bearings would have its fundamental period fall into this range of a design spectrum.

Numerical results for the specific building subjected to the El Centro earthquake of 1940 are presented. Both the time history and the response spectrum modal superposition analysis were performed. In the response spectrum analysis, the Complete Quadratic Combination (CQC) showed superiority over the Square Root of the Sum of Squares (SRSS) in estimating maximum responses.

It is concluded that the effect of torsional coupling on the transient response of base isolated structures is insignificant, due to the combined effect of the time lag between the maximum translational and torsional responses and the influence of damping in the isolation system which for elastomeric bearings can be as high as 8 to 10 per cent.
Vibration of beams on non‐homogeneous elastic foundations
Authors: Pavlović Milija N. , Wylie Gordon B.
Published: March 2007

The natural response of a beam or pile supported by an elastic foundation is investigated for the case when the coefficient of subgrade reaction varies linearly along the span of the member.
Effects of reservoir bottom absorption on earthquake response of concrete gravity dams
Authors: Fenves Gregory , Chopra Anil K.
Published: March 2007

A procedure is presented to analyse the response of concrete gravity dams due to horizontal and vertical earthquake ground motion components considering dam‐water interaction and partial absorption of hydrodynamic pressure waves at the reservoir bottom into the foundation medium. The effects of reservoir bottom absorption on the hydrodynamic force on a rigid dam are examined first. The harmonic response of an idealized dam cross‐section is presented for a wide range of parameters characterizing the properties of the dam, the impounded water and the foundation medium. Based on these frequency response functions the effects of dam‐water interaction and of reservoir bottom absorption in the response of dams due to horizontal and vertical components of ground motion are investigated.
Load spectra for slender offshore structures in waves and currents
Authors: Taylor R. Eatock , Rajagopalan A.
Published: March 2007

The influence of currents on the wave induced dynamic response of offshore structures with slender members is assessed by deriving appropriate load spectra. The analysis permits the implications of the modified Morison equation to be examined, and suggests that methods of equivalent linearization commonly employed may yield unconservative results. An alternative formulation is proposed, in which the equations of motion are linear in the structural kinematics but the non‐linear dependence of drag force on fluid particle motions is retained. This leads to a load spectral density matrix expressed as a sum of terms, involving convolutions of the wave kinematics spectra. Results are obtained for a plane frame idealization of an offshore jacket structure. These demonstrate the strong influence of current, and the importance of retaining in the loading terms up to the third power of wave particle velocity.
Vibration of thermally stressed polar orthotropic annular plates
Authors: Gorman D. G.
Published: March 2007

This study sets out to analyse the effect of uniform temperature on the natural frequencies of transverse vibration of uniform polar orthotropic annular plates. The method employed is that of the annular finite element technique whereby the flexural and membrane components of the solution are separated. By close examination of the form of the resulting in‐plane stress distribution due to the thermal loading, it has been possible to obtain results for a wide selection of specimens by way of one equation and three graphs.
Effect of topography and subsurface inhomogeneity on seismic rayleigh waves
Authors: Ohtsuki Akira , Yamahara Hiroshi , Harumi Kasaburo
Published: March 2007

The effect of topography and subsurface inhomogeneity on surface motion is investigated in the case of Rayleigh waves. In the previous paper, the same effect was investigated in the case of SV waves. Several types of topography, such as cliffs both with and without a soft layer at the foot of the slope, are considered. Computations are made using a new hybrid method combining a particle model with a finite element method. In cases of harmonic Rayleigh waves, surface motions with amplitudes as large as 1.5 to 5 times the horizontal surface displacement of the incident Rayleigh waves are produced near the slope and the sloping interface. When a Rayleigh wave propagating through a hard single‐layered ground encounters a sloping interface where hard ground and soft ground make contact with each other, Rayleigh waves having two different, phase velocities are produced and they correspond to the fundamental mode, and the first mode determined by Haskell's method. In addition, the transient response when Rayleigh waves propagate through the cliff is also simulated. Assuming the vertical component of the Tokachi‐oki Earthquake (1968) measured on the surface to be a Rayleigh wave, the incident Rayleigh wave can be obtained by a Fourier synthesis of eigenfunctions of Rayleigh waves.
Dynamic response of 3‐D rigid surface foundations by time domain boundary element method
Authors: Karabalis D. L. , Beskos D. E.
Published: March 2007

The dynamic response of three‐dimensional rigid surface foundations of arbitrary shape is numerically obtained. The foundations are placed on a linear elastic, isotropic and homogeneous half‐space representing the soil medium and are subjected to either external dynamic forces or seismic waves of various kinds and directions, with a general transient time variation. The problem is formulated in the time domain by the boundary element method and the response is obtained by a time step‐by‐step integration. Two examples dealing with three‐dimensional rectangular foundations are presented in detail, together with comparisons with other methods, in order to document the accuracy of the method. The main advantages of the proposed method are that, unlike frequency domain techniques, it provides directly the transient response and forms the basis for extension to the case of non‐linear behaviour.
Effect of epicentral direction on seismic response of asymmetric buildings
Authors: Di Paola M. , Muscolino G.
Published: March 2007

The paper deals with the influence of the epicentral direction on the displacement and stress response of multistorey asymmetric buildings to earthquake horizontal ground motion.

A method is given for computing for each plane frame of the complex structure a particular direction of the bidirectional stationary random input for which the horizontal floor displacement of the given frame is maximized. It is shown that this direction can be considered conservative for the corresponding non‐stationary process.
An exact numerical time integration of scalar equations for undamped structural systems
Authors: Kujawski Jerzy , Desai Chandrakant S.
Published: March 2007

An exact numerical time integration of scalar equations for undamped structural systems is presented. Typical numerical examples are included to illustrate the use of the proposed procedure.
Cladding influence on dynamics response of tall buildings
Authors: Palsson Hafsteinn , Goodno Barry J. , Craig James I. , Will Kenneth M.
Published: March 2007

Precast concrete panels form attractive facades for steel frame buildings and are generally regarded as non‐structural by structural engineers. However, panels have been found to add lateral stiffness until their capacity or that of their connections is exceeded. Consequently, the computed dynamic response based on a model of the structural framing alone may be quite different from that experienced by the actual structure.

As a case study, the influence of precast concrete panels on lateral and torsional stiffness of a 25‐storey building was investigated. The effect of cladding on dynamic properties and linear seismic response was explored by varying panel stiffness. Cladding stiffness was added to the bare frame model until analytical frequency values matched vibration test results. Then, using the cladding stiffness values obtained, an accidental eccentricity between centres of mass and rigidity at each floor level was imposed and linear seismic response computed. Torsional response effects were increased substantially. Finally, a modified cladding panel connection was developed based on previously‐reported studies for panelized construction. The influence of the proposed connection on overall structural response was determined for different ground motion inputs.
An alternative approach to the random response of bilinear hysteretic systems
Authors: Asano Koichiro , Iwan Wilfred D.
Published: March 2007

An analytical representation of the bilinear hysteretic characteristic is presented. Using this representation, the response of a single‐degree‐of‐freedom bilinear hysteretic system subjected to non‐stationary random excitation is examined by equivalent linearization. An ordinary differential equation is derived for the covariance matrix of the response. Numerical examples are presented and the accuracy of the approach is demonstrated. Extension of the approach to a wider class of hysteretic systems is discussed.
Earthquake response of structures with partial uplift on winkler foundation
Authors: Yim Chik‐Sing , Chopra Anil K.
Published: March 2007

The effects of transient foundation uplift on the earthquake response of flexible structures are investigated. The structural idealization chosen in this study is relatively simple but it incorporates the most important features of foundation uplift. In its fixed base condition the structure itself is idealized as a single‐degree‐of‐freedom system attached to a rigid foundation mat which is flexibly supported. The flexibility and damping of the supporting soil are represented by a Winkler foundation with spring‐damper elements distributed over the entire width of the foundation. Based on the response spectra presented for several sets of system parameters, the effects of foundation‐mat uplift on the maximum response of structures are identified. The influence of earthquake intensity, structural slenderness ratio, ratio of foundation mass to structural mass, foundation flexibility and p‐δ effects on the response of uplifting structures is also investigated.
Seismic analysis of a rotor‐bearing system
Authors: Srinivasan V. , Soni A. H.
Published: March 2007

The seismic analysis of a rotor‐bearing system is presented in the time domain. The governing equations of motion for the rotor are derived including the effects of rotatory inertia, shear deformation, gyroscopic effects, axial force, axial torque, stiffness and damping provided by the lubricants in the bearings, base translation and base rotation. A simple and efficient finite rotor element based on a Galerkin formulation is proposed to model the rotor. The effects of disks and flywheels mounted on the rotor are also included in the analysis. An example problem for a rotor‐bearing system is solved using El Centro earthquake data. Four cases are investigated that will permit one to study the influence of spin, base rotation, comparison between rigid body model and beam model and the influence of axial force and axial torque. The results of the above study show that the gyroscopic effects amplify the response of the rotor‐bearing system. The base rotations of the rotor‐bearing system under seismic excitation contribute significantly to the response.
A linear mathematical model for the seismic inplane behaviour of brick masonry walls part 1: Theoretical considerations
Authors: Mengi Yalcin , Sucuoǧlu Haluk , McNiven Hugh D.
Published: March 2007

In this study two mathematical models are presented for the linear dynamic behaviour of masonry walls. The study is completed in three stages: experimental observations, selection of a mathematical model and the determination of model parameters through optimization analysis. In the present paper (Part 1) the theoretical analysis used in the development of the mathematical models is presented. Part 2 is devoted to the optimization analysis.

Evaluation of the experimental data, which is described in detail in Part 2, indicates that the first two modal frequencies of the wall specimen are close to each other. This may be attributed, on physical grounds, to strong interaction between the brick and mortar phases of the wall. Accordingly, a two‐phase mathematical model, namely a mixture model (MM), is chosen to describe the wall behaviour because it can differentiate between the two phases of the wall and take into account the interaction between them. The equations of MM are put into a discrete form to simplify the optimization analysis. As a special case, MM contains a simple one‐phase model called the effective modulus model (EMM). The equations of EMM are also established. Finally, the theoretical complex frequency response functions (CFRF) predicted by MM and EMM are obtained. CFRF relates the top acceleration of the wall to its base acceleration and is the response quantity chosen to be matched in the optimization analysis.
A linear mathematical model for the seismic inplane behaviour of brick masonry walls part 2: Determination of model parameters through optimization using experimental data
Authors: Sucuoǧlu Haluk , Mengi Yalcin , McNiven Hugh D.
Published: March 2007

The parameters appearing in the mixture and effective modulus models proposed in Part 1 are determined through optimization by matching theoretical and experimental responses. The optimization analysis is performed in frequency space. The response quantities chosen to be matched are the complex frequency response functions (experimental and theoretical) relating the Fourier transforms of top and base accelerations of the wall. Computations in optimization analysis are carried out by introducing an object (error) function and minimizing it using the Gauss‐Newton method. The results show that the mixture model is capable of predicting accurately the dynamic response of masonry walls up to a frequency which is well above the second modal frequency, whereas the effective modulus model describes the wall behaviour only up to the first modal frequency. Furthermore, it is shown that the mixture model is still valid when micro cracks, which may exist between the mortar and brick constituents, are present.
Dynamic‐stiffness matrix of soil by the boundary‐element method: Conceptual aspects
Authors: Wolf John P. , Darbre Georges R.
Published: March 2007

Starting from a weighted‐residual formulation, the various boundary‐element methods, i.e. the weighted‐residual technique, the indirect boundary‐element method and the direct boundary‐element method, are systematically developed for the calculation of the dynamic‐stiffness matrix of an embedded foundation. In all three methods, loads whose analytical response in the unbounded domain can be determined are introduced acting on the continuous soil towards the region to be excavated. In the weighted‐residual technique and in the indirect boundary‐element method, a weighting function is used; in the latter case, it is selected as the Green's function for the surface traction. In the direct boundary‐element method, the surface traction along the structure‐soil interface is interpolated. The same type of boundary matrices which have a clear physical interpretation are identified in the three formulations, each of which is illustrated with a simple static example.

The indirect boundary‐element method leads to the most accurate results. The guaranteed symmetry and the fact that the displacement arising from the applied loads can easily be calculated and compared to the prescribed displacement makes the indirect boundary‐element method especially attractive for calculating the dynamic‐stiffness matrix of the soil.

Instead of calculating the dynamic‐stiffness matrix of the embedded foundation with the boundary‐element method, it can be determined as the difference of those of the regular free field and of the excavated part. The calculation of the former does not require the Green's function for the surface traction. The dynamic stiffness of the excavated part can be calculated by the finite‐element method.
On the solution of approximated systems when using reduced component modes
Authors: Martin K. F. , Ghlaim K. H.
Published: March 2007

The work described in this paper relates to the computation of vibrational characteristics of a system which consists of components connected together elastically. The vibrational characteristics of each component are known and these are used via matrix manipulation to find the system characteristics. This particular paper confines itself to examining the matrix manipulation in detail and it is shown that the mass normalized modal matrix [Ψ] and connection matrix [C] can be contracted in size without affecting the overall solution. When the system is approximated by deleting rows and columns from the involved matrices, it is confirmed analytically that which rows are deleted from the mass normalized modal matrix [Ψ] has no relevance to the approximate solution for the system.
Response to wind of a model chimney with added damping
Authors: Dosanjh H. , Johns D. J.
Published: March 2007

Some ad hoc studies are reported which investigated the use of added damping layers at the base of a wind‐tunnel model of a chimney as a means of increasing its overall structural damping. Significant increases in the logarithmic decrement were obtained from decaying free‐vibration tests and in subsequent wind‐tunnel tests corresponding decreases in wind‐excited tip response were measured.

It was concluded that the technique is promising for wind‐tunnel parametric studies in which significant changes in the structural damping are required and recommends further work.
A comparison of approximate techniques for non‐linear seismic soil response
Authors: Corsanego Alfredo , Solari Giovanni , Stura Dino
Published: March 2007

Some equivalent linearization techniques, applicable to problems dealing with non‐linear seismic amplification of layered soils, are systematically treated and critically compared in this paper. The discussion concerns, in particular, the theoretical consistency, the operative modalities, the computational complexity and the numerical reliability of these methods.

A comparison is made between the results furnished by some techniques among those examined and the results obtained through a step‐by‐step integration of the non‐linear equations of motion, assuming as a test‐problem the one‐dimensional amplification of a horizontally stratified soil deposit characterized by the Ramberg‐Osgood constitutive model.
The generation of spectrum compatible accelerograms for the design of nuclear power plants
Authors: Preumont André
Published: March 2007

Based on the main features of the computer program THGE, the paper reviews the techniques which are available for the construction of an accelerogram whose response spectrum matches a design spectrum. First, a sample accelerogram is generated as the product of the stationary random sequence by a deterministic shape function. It is assumed that the spectral properties of the stationary process have been determined in a previous step, in order to lead to the design spectrum as expected maximum responses of a set of single degree of freedom oscillators. The principal properties of the Fast Fourier Transform which is used for this first step are reviewed. The paper then describes the procedures which are available, both in the frequency domain and in the time domain, to improve the agreement between the response spectrum and the target. It also discusses some related issues, such as the response spectrum calculations, the statistical dependence between the three earthquake components, the duration of the time history, the variability of the secondary response to various samples and the generation of an accelerogram whose response spectra envelop a set of design spectra. The point of view adopted is the one of the structural engineer.
Use of ritz vectors in wave propagation and foundation response
Authors: Bayo E. P. , Wilson E. L.
Published: March 2007

The accuracy of a numerical method is demonstrated for the dynamic analysis of large complex finite element systems in which the spatial distribution of the loading is constant. The method is based on the use of a special class of Ritz vectors which were previously proposed and can be generated with minimum numerical effort. The purpose of this paper is to extend the use of these vectors to the solution of wave propagation and foundation response problems.

The method is applied to one‐, twoand three‐dimensional problems in order to illustrate the efficiency and accuracy of the technique. Unless it is necessary to evaluate the very high‐frequency behaviour of a structural system, it is shown that a small number of Ritz vectors will produce excellent results. Therefore, they can be very effective in the solution of three‐dimensional soil‐structure systems subjected to earthquake loading.
Complex response analysis of shells of revolution including uniform base translation and rocking
Authors: Lee Bor‐Jen , Gould Phillip L.
Published: March 2007

A complex response algorithm for the dynamic analysis of axisymmetric thin shells supported on an interactive foundation is developed. The substructure deletion method is employed through the utilization of a dynamic boundary system at the contact area between the superstructure and the substructure. A new mathematical formulation in conjunction with the shell behaviour is developed to deal with rigid body motions due to the negation of the fixed base assumption. Four foundation conditions, that is, a fixed base, two pile foundation cases and a flexible base, are to examine the effect of base flexibility on the seismic response of cooling towers. Also, excellent comparative results between the frequency domain solution and a time domain solution are obtained.
Efficient analysis of dynamic response of linear systems
Authors: Veletsos Anestis S. , Ventura Carlos E.
Published: March 2007

After reviewing briefly a recently proposed procedure for evaluating the dynamic transient response of a classically damped linear system from its corresponding steady‐state response, a modified procedure is presented which also appears to be highly efficient for non‐classically damped systems of the type encountered in studies of soil‐structure interaction. The concepts involved are developed by reference to viscously damped single‐degree‐of‐freedom systems, and numerical solutions are included to illustrate the accuracy and efficiency of the proposed procedure and its superiority over the classical Discrete Fourier Transform approach.
Low‐frequency transfer of seismic energy by superficial soil deposits and soft rocks
Authors: Mohammadioun Bagher , Pecker Alain
Published: March 2007

Recordings of recent strong earthquakes obtained on alluvial sites show that the maximum horizontal accelerations tend towards a limit of about 0.45 to 0.50g, associated with large displacements. by contrast, vertical accelerations do not appear to be subject to such a limit (1.7g for the 1979 Imperial Valley earthquake). Theoretical linear elasticity models, when applied to superficial layers of low strength, seem to be inadequate for the prediction of near‐field ground motions in alluvial deposits. A good approximation for the horizontal component of certain Imperial Valley records was, however, obtained through a non‐linear approach, using local soil properties together with a reasonable hypothesis for motion at the base of the superficial layers in question that included large values of acceleration for high‐frequency shear waves.
Dynamic analysis of structures using lanczos co‐ordinates
Authors: Nour‐Omid Bahram , Clough Ray W.
Published: March 2007

A procedure for deriving the Lanczos vectors is explained and their use in structural dynamics analysis as an alternative to modal co‐ordinates is discussed. The vectors are obtained by an inverse iteration procedure in which orthogonality is imposed between the vectors resulting from successive iteration cycles. Using these Lanczos vectors the equations of motion are transformed to tridiagonal form, which provides for a very efficient time‐stepping solution. The effectiveness of the method is demonstrated by a numerical example.
Dynamic eccentricity of structures subjected to S‐H waves
Authors: Wu S. T. , Leyendecker E. V.
Published: March 2007

The behaviour of coupled lateral‐torsional systems subjected to seismic waves is investigated analytically. This paper present numerical results of a few case studies which show the contributions of each of the selected parameters to the rotational response of the structural systems. Dynamic eccentricity is used as an index to represent the level of the rotational response. Accidental eccentricities due to S‐H waves are evaluated. Design implications based on this study are also given.
Vibrations of corner point supported shallow shells of rectangular planform
Authors: Narita Yoshihiro , Leissa Arthur W.
Published: March 2007

The first known solution of the title problem is presented. The Ritz method is used, with algebraic polynomials forming the set of trial functions. The condition that all three components of displacement be zero at the four corners is straightforwardly enforced. Numerical studies show that the convergence is relatively slow, requiring more terms than for shells which are completely free. The class of problems studied includes independent, constant curvature in each of the directions parallel to the edges, yielding vibration modes which fall into one of four symmetry classes, with symmetry or antisymmetry of the displacements existing with respect to each of the two symmetry axes of the problem. Detailed results are given for the frequencies and mode shapes of the first two modes of each symmetry class for shells having square planform and circular cylindrical, spherical and hyperbolic paraboloidal curvatures. Accuracy of the results is partially established by comparison with other previously published, accurate results for the corner supported flat square plate.
Modal base forces in structures having a straight‐line mode of vibration
Authors: Darbre Georges R.
Published: March 2007

The modal base forces in structures having a straight‐line mode of vibration are investigated. Making use of the orthogonality relationship between the different modes, a relation between the modal base shears and base moments is found in all but the straight‐line mode. This relation states that the contribution of the inertia forces to the modal overturning moments referred to the centre of rotation of the straight‐line mode is identically null. The contributions of the vertical forces and lateral constraints must, however, be accounted for. For the special case of the straight‐line mode being proportional to the height of each storey, the centre of rotation coincides with the base of the structure. For the case of the straight‐line mode being a uniform displacement, the centre of rotation is at infinity and the contribution of the inertia forces to the modal base shears identically disappears in all but the straight‐line mode.
Groundborne vibrations due to trains in tunnels
Authors: Chua K. H. , Balendra T. , Lo K. W.
Published: April 2007

An analytical procedure is presented for determining groundborne vibrations in buildings due to subway trains. The procedure involves a finite element idealization of the subway‐soil‐structure interaction problem, using an analytical model for the train loading spectrum at the tunnel invert. Both direct fixation and floating slab track support systems are considered. The train model is verified using the measurements of rail velocities. The proposed procedure is applied to the case of a four‐storey podium block enclosing twin double‐box subways within the confines of its ribbed wall foundations. The severity of velocity response levels of the building, in relation to vibration standards, is also considered.
Wave dispersion and optimal mass modelling for one‐dimensional periodic structures
Authors: Fukuwa Nobuo , Matsushima Shinichi
Published: April 2007

Discrete analysis methods are frequently used for the study of the structure and soil. However, the assumption of the displacement interpolation function makes the waves dispersive, which means the numerical dispersion. The wave dispersion induced by the discretization depends on the mass modelling. Also, the existence of added lumped masses makes waves dispersive even for the continuum modelling. In order to examine these wave dispersions, a one‐dimensional periodic structure is adopted as an analysis model and the dynamic transfer matrix method is applied. A wave solution and a finite element solution are used for the evaluation of the transfer matrix. The phase and group velocities in the structure are explicitly represented. These values are compared among the continuum modelling and the discretization modelling in which several consistent mass ratios are adopted. The optimal consistent mass ratio, which makes the wave velocity of the discrete model the same as that of the continuum model, is newly developed here. The validity of this mass modelling technique is presented by examining the frequency response function and impulse response function.
Chemical composition and antimicrobial activity of the essential oil from aerial parts of Micromeria fruticulosa (Bertol.) Grande (Lamiaceae) growing wild in Southern Italy
Authors: Formisano Carmen , Mignola Enrico , Rigano Daniela , Senatore Felice , Bellone Gabriella , Bruno Maurizio , Rosselli Sergio
Published: April 2007

The essential oil of aerial parts of Micromeria fruticulosa (Lamiaceae) growing wild in Southern Italy was obtained by hydrodistillation and analysed by GC and GC–MS. Sixty‐one compounds, representing 91.3% of the oil, were identified. The major components were γ‐terpinene (14.5%), β‐caryophyllene (12.6%), p‐cymene (8.9%), α‐pinene (8.2%) and β‐bisabolene (7.2%). The essential oil showed action mainly against Gram‐positive bacteria. Copyright © 2007 John Wiley & Sons, Ltd.
Diversification patterns of Early and Mid Ordovician graptolites in South China
Authors: Yuandong Zhang , Xu Chen , Goldman Daniel
Published: March 2007

During the Early and Mid Ordovician, graptoloids underwent a dramatic diversification. Many clades (e.g. anisograptids, dichograptids and biserials) originated and subsequently diversified during this interval, playing the most important roles in the evolution history of graptolites. In this study we conduct an analysis of the generic and species diversity history of Early to Mid Ordovician graptolites from the Yangtze Region (platform) and Jiangnan Region (slope) of South China, and provide evidence that the regionally distinct biodiversification patterns are related to the different representative environments of each region.

Graptolite diversity measured across graptolite zones displays a remarkable increase in both regions during the Early to Mid Ordovician, but with distinct scales and patterns in each region. In the Upper Yangtze Region, the diversification is less rapid and can be divided into four phases. The second major diversification phase (early Arenig) is characterized by the rapid expansion of dichograptids, and the fourth diversification phase (mid‐late Darriwilian), which is preceded by a decline (third phase), is typified by the flourishing of biserial graptolites. The diversification of graptolites in the Jiangnan Region is more dramatic and shows a distinct pattern of rapid, progressive and sustained diversity rise from the early Arenig to the early Darriwilian. This rapid diversification is initially driven by the expansion of dichograptids and subsequently enhanced by the significant addition of glossograptids and diplograptids.

A comparison of diversity patterns between the Upper Yangtze Region, the Jiangnan Region, Australasia, Baltoscandia and Avalonia indicates: (1) the global Arenig expansion of dichograptids is also recorded in South China, (2) the diversity pattern of the Upper Yangtze Region is largely comparable to that of Baltoscandia and Avalonia, but is considerably different from that of Australasia, and (3) the sustained rapid increase of graptolite diversity in the Jiangnan Region is not shared by any of the other regions. Copyright © 2007 John Wiley & Sons, Ltd.
The role of patient personality in the identification of depression in older primary care patients
Authors: McCray Laura W. , Bogner Hillary R. , Sammel Mary D. , Gallo Joseph J.
Published: April 2007

Background

Our aim was to evaluate whether personality factors significantly contribute to the identification of depression in older primary care patients, even after controlling for depressive symptoms.

Methods

We examined the association between personality factors and the identification of depression among 318 older adults who participated in the Spectrum study.

Results

High neuroticism (unadjusted Odds Ratio (OR) 2.36, 95% Confidence Interval (CI) [1.42, 3.93]) and low extraversion (adjusted OR 2.24, CI [1.26, 4.00]) were associated with physician identification of depression. Persons with high conscientiousness were less likely to be identified as depressed by the doctor (adjusted OR 0.45, CI [0.22, 0.91]).

Conclusion

Personality factors influence the identification of depression among older persons in primary care over and above the relationship of depressive symptoms with physician identification. Knowledge of personality may influence the diagnosis and treatment of depression in primary care. Copyright © 2007 John Wiley & Sons, Ltd.
Phosphatidylcholine‐specific phospholipase C and ROS were involved in chicken blastodisc differentiation to vascular endothelial cells
Authors: Zhao Jing , Zhao Baoxiang , Wang Weiwei , Huang Bin , Zhang Shangli , Miao Junying
Published: March 2007

To find the key factors that were involved in the survival and vascular endothelial differentiation of chick blatodisc induced by fibroblast growth factor 2 (FGF‐2), we built a chick vasculogenesis model in vitro. Subsequently, the activities of phosphatidylcholine‐specific phospholipase C (PC‐PLC), including Ca2+‐dependent and ‐independent PC‐PLC, and the level of reactive oxygen species (ROS) were evaluated during the endothelial differentiation of chick blastodisc. The results showed that Ca2+‐indepentent PC‐PLC underwent a remarkable increase in 24 h (P < 0.01), then it decreased gradually with the cell differentiation, while the Ca2+‐depentent PC‐PLC was nearly not changed in the whole process. At the same time, ROS level dramatically decreased during the cell differentiation. To understand the role of PC‐PLC and how it performs its function in the vascular endothelial differentiation induced by FGF‐2, we suppressed PC‐PLC activity by its specific inhibitor D609 (tricyclodecan‐9‐yl potassium xanthate) at 24 h during the cell differentiation. As a result, the cell differentiation could not progress and the intracellular level of ROS was elevated. The data suggested that PC‐PLC and ROS were involved in chicken blastodisc differentiation to vascular endothelial cells. PC‐PLC was an important factor in the blastodisc cell survival and differentiation, and it might perform its function associated with ROS. J. Cell. Biochem. 102: 421–428, 2007. © 2007 Wiley‐Liss, Inc.