bluuebunny/crossref_metadata_2025 huggingface dataset:
A hybrid modelling of soil–structure interaction problems for deeply embedded structures in A multilayered medium
Authors: Romanel Celso , Kundu Tribikram
Published: April 2007

Dynamic response of deeply embedded structures, such as underground tunnels and deep foundations, in a multilayered elastic half‐space are analysed when the structure is excited by a plane P or SV wave propagating at some angle. The scattered field is represented by the sum of three Green's functions, corresponding to two oscillating forces and one oscillating moment at the centroid position of the buried structure. The amplitudes of these two forces and one moment are a priori unknown and are obtained by satisfying displacement and stress continuity conditions across the near‐field/far‐field boundary. The distinguishing feature of this technique from direct or indirect boundary integral techniques is that in these techniques a distribution of sources of unknown amplitude are considered at the near‐field/far‐field boundary, and a large number of sources are needed for different combinations of source‐receiver arrangements. But in this technique the sources of unknown amplitude are placed at the location of the structure, not at the near‐field/far‐field boundary and, using the Saint Venant's principle, the scattered field is modelled. Thus, the number of sources required is reduced to only three. Two example problems are solved. The first one is for a deeply embedded footing in a three‐layer soil mass and the second one is for a rectangular tunnel in a two‐layer soil mass.
Linear system response by DFT: Analysis of A recent modified method
Authors: Hall John F. , Beck James L.
Published: April 2007

An analysis of a recent modified frequency‐domain procedure for computing the response of linear systems using the fast Fourier transform (FFT) algorithm is described. This modified procedure eliminates the appended free‐vibration interval that is used in the standard approach. The duration of the period of computation still needs to be longer than that of the response interval of interest, but only slightly. Reducing the period of computation lowers the number of frequencies at which the transfer function needs to be defined. The major drawback of the method is a high sensitivity to errors in the computed values of the transfer function, which reduces the role of interpolation in the transfer function definition. The modified method is related to the discrete Laplace transform.
Dynamic behaviour and seismic response of El Infiernillo dam
Authors: Elgamal Ahmed‐W. M. , Gunturi Ramana V.
Published: April 2007

El Infiernillo, a 145 m high rockfill dam in Mexico built in a narrow V‐shaped canyon, was subjected to eight major earthquakes since its construction. In this study, the dynamic dam response is analysed using (i) the recorded November 15, 1975 bedrock‐crest acceleration histories and (ii) the results of a 1970 full‐scale test conducted by UNAM, in which eight upstream–downstream and longitudinal resonant frequencies and configurations were observed and documented. These observed and seismically induced dynamic responses are compared herein to predictions of two different numerical models of El Infiernillo dam; a newly developed simplified three‐dimensional (3D) model, and a 3D finite element model. The dynamic dam response characteristics are assessed, and performance of the employed numerical models is evaluated. It is found that (i) higher modes of vibration had participated significantly in the recorded seismic response and (ii) upstream–downstream response is well represented by the two numerical models employed. Using the simplified model, the September 19, 1985 earthquake non‐linear response is computed and shown to compare satisfactorily with its recorded counterpart in the upstream‐downstream and vertical directions. The largest computed dynamic accelerations, stresses and strains are found to occur within the upper third of the dam body.
A modal combination rule for spatially varying seismic motions
Authors: Berrah Mounir K. , Kausel Eduardo
Published: April 2007

The spatial variability of seismic ground motion is an important aspect for the earthquake resistant design of extended facilities. A modified response spectrum model, which addresses the problem of multiply supported structures subjected to imperfectly correlated seismic excitations, has already been developed (see References 1 and 2). The present paper proposes a modal combination rule for the case of non‐uniform seismic input, which would be used together with the modified response spectrum model in order to compute physical responses. This rule, which accounts for modal cross‐correlations, is an extension to an existing rule for the case of uniform seismic motions. It modifies the existing modal cross‐correlation coefficients through a correction factor which depends on structural properties and on the characteristics of the wave propagation phenomenon. Finally, some practical considerations on the theoretical development are addressed. They aim at suggesting reasonable simplifications which render the modal combination rule more appealing for engineering purposes. The proposed practical combination rule is validated through a numerical experiment which also characterizes the effect of non‐uniform seismic input on modal cross‐correlation.
Results from field testing A curved box girder bridge using simulated earthquake loads
Authors: Richardson James A. , Douglas Bruce M.
Published: April 2007

This paper presents the results of a unique field test on a curved highway overpass. In the test, large horizontal loads were applied to the superstructure of the bridge and quickly released, causing the bridge to vibrate. The resulting large‐amplitude vibrations were intended to be similar to the vibrations caused by earthquakes (horizontal accelerations of up to 25 per cent of gravity were measured on the bridge deck). Well‐defined lateral, longitudinal, vertical and torsional vibration modes were identified from the test data.

The vibration modes were used to verify an analytical model of the bridge's dynamic response. For this paper, the model was verified using only the fundamental vibration mode, which was primarily a horizontal vibration mode. Using a system identification procedure, the dynamic response model was adjusted until its frequency and mode shape matched the measured frequency and mode shape. Parameters in the verified model were compared with the same parameters calculated from information in the structural drawings. Because the fundamental mode represents a horizontal mode, the bridge parameters identified in this paper were those parameters which strongly influence the horizontal response of the bridge.
Green's function of support‐excited structures with tuned‐mass dampers derived by A perturbation method
Authors: Tsai Hsiang‐Chuan
Published: April 2007

A tuned‐mass damper is a small damped spring‐mass system which vibrates in resonance with the main structure to which it is attached so as to be able to dissipate vibration energy and reduce the structural response. In this paper, explicit forms of Green's function for the transient response of main structures equipped with the tuned‐mass damper and subjected to support excitation are derived by perturbation techniques and provide an insight into the characteristics of the damper. It is found that there exists a critical damping level for the tuned‐mass damper. If the damper damping is higher than this critical damping level, increasing the damper damping will enhance the structural response. When the damper damping is below this critical value, something called ‘beat phenomenon’ occurs where the structure will have a smaller response in the first beat cycle, but have a higher rebound in the following beat cycles.
Earthquake response of tension‐leg‐platforms in steady currents
Authors: Venkataramana Katta
Published: April 2007

Dynamic response of tethers of tension‐leg‐platforms to current and horizontal earthquake excitations is investigated. The static deflected shape of tether under a steady current is firstly identified. Next dynamic analysis for earthquake input is carried out for this deflected tether. The fluid loading due to surrounding water is included in the analysis as an added mass term and a hydrodynamic damping term. The tether is discretized by lumping masses at selected nodes. The platform is represented by a mass at the top end of the tether. The effect of pretension in the tether is taken into account in the form of a geometric stiffness term. At each node three degrees of freedom corresponding to surge, heave and pitch motion are considered. As the vibration modes and hence the responses are likely to be affected by the foundation characteristics, the study is extended to include the dynamic soil–structure interaction. The dynamic equations of motion for the tether–pile–soil system are derived using the substructure method. The natural frequencies and the vibration mode shapes of the total system are determined by eigenvalue analysis. The input ground acceleration is represented by Tajimi–Kanai's power spectrum for stationary conditions. The response analysis is carried out using the frequency‐domain random‐vibration approach. The coupled axial and lateral responses are evaluated for horizontal ground excitations. Numerical results indicate that the horizontal displacements of the tether increase with the input ground acceleration, but are nearly equal for all the cases of current velocities considered in the study; the vertical displacements however increase rapidly with the increase in current velocity. For the model considered in the present study, the responses are reduced when soil–structure interaction is included in the analysis.
Effect of transverse load‐resisting elements on inelastic earthquake response of eccentric‐plan buildings
Authors: Correnza J. C. , Hutchinson G. L. , Chandler A. M.
Published: April 2007

The accurate evaluation of code torsional provisions for plan‐eccentric structures exhibiting inelastic response relies on the adoption of appropriate systems defining both the torsionally balanced (reference) and torsionally unbalanced cases. Whilst a considerable number of analytical studies of this problem have been presented in the literature, inconsistencies have arisen in their conclusions. It is evident from a review of previous studies that one factor contributing significantly to these discrepancies arises in the definition of the structural layout. An issue of particular importance is whether the transverse load‐resisting elements oriented perpendicular to the assumed (lateral) direction of earthquake loading should, for purposes of realism, be included in model definitions. Given the diverse approaches in the existing literature, clarification of this issue is required in order to advance the understanding of inelastic torsional response behaviour and to assist the interpretation and comparison of previous studies. This paper aims to provide such clarification, based on analyses of a series of models defined rigorously according to code design provisions. Such models have been subjected to both uni‐ and bi‐directional ground motion input. It is concluded that for the flexible‐edge element, accurate estimates of additional ductility demand arising from torsional effects may be obtained from uni‐directional models (in which both the transverse elements and the corresponding earthquake component are neglected) only for medium‐period to long‐period systems. Such estimates may be over‐conservative for short‐period systems, which constitute a large proportion of systems for which code static torsional provisions are utilized. It is further concluded that models incorporating the transverse elements but analysed under uni‐directional lateral loading may underestimate by up to 100% the torsional effects in such systems, but are reasonably accurate for medium‐ and long‐period structures.
Soil–pile interaction during the passage of rayleigh waves: An analytical solution
Authors: Makris Nicos
Published: April 2007

A simple analytical solution is presented to calculate the single‐pile response when excited by the passage of Rayleigh seismic waves. Closed‐form expressions for the horizontal and vertical displacement distributions are presented for piles with finite or infinite length. The analytical results for both free‐head and fixed‐head piles are obtained through a dynamic Winkler model, with realistic frequency‐dependent ‘springs’ and ‘dashpots’. The results of the presented method are in excellent agreement with results of a rigorous solution. It is shown that in vertical motion, the differences between pile and soil displacements are far more significant than in horizontal motion, and therefore, further work is needed to investigate the importance of pile‐soil‐pile interaction (group effects), because of the vertical component of Rayleigh seismic waves.
Dynamic stiffness matrices for two circular foundations
Authors: Liou Gin‐Show
Published: April 2007

A systematic procedure is presented for generating dynamic stiffness matrices for two independent circular foundations on an elastic half‐space medium. With the technique reported in References 1–3, the analytic solution of three‐dimensional (3D) wave equations satisfying the prescribed traction due to the vibration of one circular foundation can be found. Since there are two analytic solutions for two prescribed tractions due to the vibrations of two circular foundations, the principle of superposition must be used to obtain the total solution. The interaction stresses (prescribed tractions) are assumed to be piecewise linear in the r‐directions of both cylindrical co‐ordinates for the two circular foundations. Then, the variational principle and the reciprocal theorem are employed to generate the dynamic stiffness matrices for the two foundations. In the process of employing the variational principle, a co‐ordinate transformation matrix between two cylindrical co‐ordinate systems is introduced. Some numerical results of dynamic stiffness matrices for the interaction of two identical rigid circular foundations are presented in order to show the effectiveness and efficiency of the present method, and some elaborations for its future extensions are also discussed.
Dynamic in‐plane racking tests of curtain wall glass elements
Authors: Pantelides C. P. , Behr R. A.
Published: April 2007

Attention has been paid recently to the potentially serious life safety and economic loss issues related to the seismic performance of ‘architectural,’ or ‘non‐structural’ building elements such as glass lites in curtain wall systems. In response, a pilot study was undertaken at the University of Missouri‐Rolla to investigate the dynamic racking performance of a 15·6 × 12·0 ft (4·56 × 3·68 m) section of curtain wall containing three 5 × 6 ft (1·52 × 1·84 m) glass panels. The curtain wall system was a ‘wide mullion’ design that had generous 1 in (25 mm) clearances between glass edges and the aluminium glazing pocket. Dynamic racking tests were performed totally in plane; no out‐of‐plane or torsional motions were included. Various types of glass specimens were tested, including annealed, heat‐strengthened and fully tempered glass in monolithic and laminated configurations. Dry glazed and two‐side structural silicone curtain walls were tested. Test results for dry glazed specimens showed that annealed and heat‐strengthened laminated glass experienced no fallout whatsoever. By contrast, annealed monolithic glass experienced frequent fallout in both small and large shards. Fully tempered monolithic glass experienced dicing, which resulted in occasional fallout of entire glass lites. Loss of rigidity in fully tempered laminated glass (when both glass plies were broken) occasionally caused entire lites to fall out. Polyester film (not anchored to the mullions) was applied to annealed monolithic glass; it prevented small shards from falling out, but sometimes contributed to entire lite fallout after the onset of severe glass cracking. Annealed laminated glass units with two‐side structural silicone glazing exhibited only very minor glass damage and no glass fallout.
Dynamic‐stiffness matrix of unbounded soil by finite‐element multi‐cell cloning
Authors: Wolf John P. , Song Chongmin
Published: April 2007

To calculate the dynamic‐stiffness matrix of the unbounded soil, a multi‐cell cloning algorithm based solely on the finite‐element formulation is developed. A non‐linear system of equations has to be solved iteratively once for the whole range of frequency. For a specific frequency, two‐ and three‐cell cloning lead to highly accurate results, which is demonstrated by examples of increasing complexity.
Dynamic displacements and stresses in the vicinity of a cylindrical cavity embedded in a half‐space
Authors: Luco J. E. , de Barros F. C. P.
Published: April 2007

The two‐dimensional response of a viscoelastic half‐space containing a buried, unlined, infinitely long cylindrical cavity of circular cross‐section subjected to harmonic plane SH, P, SV and Rayleigh waves is obtained by an indirect boundary integral method based on the two‐dimensional Green's functions for a viscoelastic half‐space. An extensive critical review of the existing numerical results obtained by other techniques is presented together with some new numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity for P, SV, SH and Rayleigh waves.
Material damping for lumped‐parameter models of foundations
Authors: Meek Jethro W. , Wolf John P.
Published: April 2007

In foundation dynamics two mechanisms of energy dissipation exist, wave radiation and material damping. Elastic continuum models of the soil capture only the radiation effect. To incorporate material damping, use is made of the fact that the dynamic‐stiffness relationships of all elastic foundations may be simulated by discrete assemblages of springs, dashpots and masses. (Such lumped‐parameter models are exact for simple cone models of the soil and approximate for more involved cases.) By application of the correspondence principle directly to the discrete elements of the lumped‐parameter model, it is possible to introduce Voigt viscoelasticity. Each original spring is augmented by a dashpot, and each original dashpot is augmented by a mass, attached in a special way. Going a step further, more realistic non‐linear‐hysteretic damping is represented by replacing the augmenting dashpots and masses by frictional elements. The analysis, which is effected solely in the time domain, is illustrated by an example from earthquake engineering.
Fourier amplitude spectra of strong motion acceleration: Extension to high and low frequencies
Authors: Trifunac M. D.
Published: April 2007

It is shown how the empirical equations for scaling the Fourier amplitude spectra in the frequency band from ∼0.1 to 25 Hz can be extended to describe the strong motion amplitudes in a much broader frequency range. At long periods, the proposed equations are in excellent agreement with (1) the seismological and field estimates of permanent ground displacement (near field) and (2) the independent estimates of seismic moment (far field). At high frequencies, f ≥ 25 Hz, the spectral amplitudes can be described by exp (− πkf), where k ranges from 0·02 (near source) to about 0·06 at an epicentral distance of about 200 km. It is also shown how amplification by local soil and geological site conditions can be defined to apply in the same broad frequency range.
Uniform‐hazard response spectra—An alternative approach
Authors: Loh Chin‐Hsiung , Jean Wen‐Yu , Penzien Joseph
Published: April 2007

An alternative method is presented for generating uniform‐hazard response spectra making use of a seismic hazard curve expressing annual probability of exceedance as a function of Peak Ground Acceleration (PGA), a set of normalized (PGA = 1g) mean response spectra, and a coefficient‐of‐variation function for the random normalized spectral values in terms of period T. The practice of using mean + 1σ normalized response spectra, scaled to specified PGA levels, is discussed and associated mean return periods are evaluated.
Source, path and site effects on dominant frequency and spatial variation of strong ground motion recorded by smart1 and smart2 arrays in Taiwan
Authors: Beresnev Igor A. , Wen Kuo‐Liang , Yeh Yeong Tein
Published: April 2007

The reduction in spatial variance of strong ground motion with increasing earthquake magnitude has been reported recently. However, we show that the observed dependence of spatial variance on magnitude is its implicit dependence on the frequency content (dominant frequency) of the wave field. Time‐domain cross‐correlations of pairs of accelerograms are used to quantify the spatial variations in this paper. Magnitude is one of the factors contributing to the dominant frequency. We attempt to study separately the effects of magnitude, hypocentral distance, peak ground acceleration and focal depth on the dominant frequency in order to find the most significant one. The data base consists of 1965 records of horizontal acceleration from 148 local earthquakes in Taiwan. The analysis shows the overwhelming effect of the source magnitude on the formation of the dominant frequency with an empirical relationship:

No significant effect of hypocentral distance, local acceleration amplitude or depth is detected for all their values available (up to 170 km, 250 cm/s2, and 100 km, respectively). The prevailing effect of magnitude on the dominant frequency is a real cause of the consistently observed reduction of spatial variance of ground motion with increasing magnitude of earthquakes.
Transient response of a group of rigid strip surface foundations
Authors: Guan F. , Novak M.
Published: April 2007

A numerical procedure is proposed to investigate the transient response of a group of rigid strip foundations resting on an elastic, homogeneous half‐space subjected to either external forces or seismic motions. A fundamental solution is presented for uniform strip loadings with Heaviside function time‐dependence applied on the half‐space. In the procedure, each of the foundations is discretized into subelements. The tractions between the half‐space and the subelements are assumed constant at every time step. The through‐soil coupling effects between the foundations are studied numerically.
The role of the stochastic equivalent linearization method in the analysis of the non‐linear seismic response of building structures
Authors: Cunha Álvaro A. M. F.
Published: April 2007

The stochastic equivalent linearization method has been significantly improved during the last two decades, leading to rather efficient and accurate estimates of the first‐ and second‐order statistical moments of the random response process, even when the non‐stationarity of the excitation and the hysteretic degrading non‐linearities of the structural system are taken into account.

The purpose of this paper, apart from presenting a short survey of the most relevant methods developed in this area, indicating their main restrictions, is to call attention to the remarkable possibilities of the equivalent linearization technique as the most powerful approximate method to deal with the seismic response analysis of MDOF non‐linear building structures, deserving to be considered by the engineering codes in the near future as an appropriate formulation for that purpose.

To illustrate the real interest of this method, several applications concerning a simple shear‐building structural model are presented, considering columns with non‐linear restoring forces, either bilinear elastic or hysteretic, and the results obtained by some computer programs developed on the basis of the equivalent linearization technique are compared with the estimates achieved by digital simulation in order to check the level of accuracy. Moreover, these results are also used to evaluate limit violation (failure) probabilities, based on the vulnerability function concept.
Rotational cone models for a soil layer on flexible rock half‐space
Authors: Wolf John P. , Meek Jethro W.
Published: April 2007

The unfolded cone model used for calculating the dynamic response of a disk on the surface of a soil layer resting on flexible rock for translational motion is extended to rotational motion. The method is analogous to that for a layer on rigid rock, the only modification being that the reflection coefficient – α replaces the coefficient of total reflection – 1. The modified value of – α, which, in general, is frequency‐dependent, is determined by considering one‐dimensional wave propagation along the cone for the first impingement at the layer–rock interface. The low‐ and high‐frequency limits of – α for the rotational motion are the same as for translational motion. As these limits do not depend on frequency, the dynamic analysis using cones can be performed in the familiar time domain. The transfer function constructed by addressing the reflections–refractions at the soil–rock interface and the reflections at the free surface in the unfolded cone model is highly accurate, resulting in the same accuracy of the dynamic response of a disk on a layer resting on flexible rock as that on a homogeneous half‐space modelled with a cone.
A robust delay‐compensation technique based on memory
Authors: Inaudi José A. , Kelly James M.
Published: April 2007

This paper addresses the effects of time delay on actively isolated structures subjected to support excitation. A force proportional to the absolute velocity of the base of the isolated structure applied at the base of the structure (co‐located active damping) is the control scheme considered. The actuating mechanisms have some non‐zero time response. Consequently, if no compensation is provided, the performance of the system is worse than that of the ideal delay‐free controller. The dynamics of the controller‐actuator system is modelled by a delay operator on the feedback signal. Time delays producing instability of the controlled structure are investigated, and the effect of time delay on the mean square acceleration of the structure subjected to stationary random excitation is assessed. A delay‐compensation technique that requires memory of past control actions is proposed and compared with a commonly used compensation technique. By using simple numerical examples, it is shown that the proposed delay‐compensation strategy improves the performance of the system significantly. The technique is extended to other models of the actuator dynamics and modified to provide robustness to small parameter uncertainties.
Application of polarization analysis in correcting the orientation error of a downhole seismometer
Authors: Chiu Hung‐Chie , Huang Huey‐Chu , Leu Chun‐Long , Ni Shean‐Der
Published: April 2007

This paper shows that the polarization analysis of later arrivals could be used to estimate the orientation error and the tilt of the downhole accelerometers in the Dahan downhole strong‐motion array. This four‐level array is located to the north of Hualien city in eastern Taiwan. Polarization analysis of a windowed signal which includes significant phases (e.g. primary S wave) can give a stable major polarization axis. This axis can then be used as the reference direction for correcting the orientation error and the tilt of the downhole seismometers. If the surface instrument is chosen as the reference, the angle between the major polarization axes of the surface and any downhole recordings will be the orientation error needed to be corrected for the downhole accelerograph. This angle is a combination of the tilt and the orientation errors which correspond to the dip and strike of maximum polarization, respectively.

At the Dahan downhole strong‐motion array, the orientation errors of the seismometers at the depth of 50, 100 and 200 m were 1°, 90° and 84°. These orientation errors were consistent with the horizontal particle‐motion analysis. The errors of horizontal plane (tilt) were almost zero. After correction, the coherency of the waveforms between the surface and the downhole recordings was significantly improved.
Dynamic characteristics of shear buildings on laminated rubber bearings
Authors: Pan Tso‐Chien , Cui Wei
Published: April 2007

Analytical solutions are derived for the dynamic characteristics of base‐isolated shear buildings supported on laminated rubber bearings. The solution process takes into account the combined effects of the superstructure flexibility and the base raft inertia on the dynamic characteristics. A series of parametric studies is carried out and the effects of varying the stiffness and mass of the base‐isolation system on the frequencies and mode shapes are identified. Approximate solutions for the fundamental base‐isolated frequency and mode shape are obtained, which are suitable for use in the preliminary design of non‐rigid base‐isolated buildings.
Understanding the inelastic seismic behaviour of asymmetric‐plan buildings
Authors: De Llera Juan C. La , Chopra Anil K.
Published: April 2007

Studied in this paper is the inelastic seismic behaviour of asymmetric‐plan buildings using the histories of base shear and torque. The first step in understanding this behaviour is to construct the base shear and torque surface (BST) for the building, which represents all combinations of shear and torque that applied statically lead to collapse of the structure. Several factors controlling the shape of this surface, such as strength eccentricity and bidirectional ground motion, are identified. Also, their effects on the building responses are studied considering several structural configurations. The results obtained show that the BST surface, in conjunction with the base‐shear and torque histories, provides a useful conceptual framework for understanding the behaviour of asymmetric systems. Furthermore, using these surfaces, relevant aspects of the behaviour and design of such buildings become apparent even before dynamic analysis of the structure.
Pseudo‐dynamic testing using conventional testing devices
Authors: Nakashima Masayoshi , Akazawa Takashi , Igarashi Hideichi
Published: April 2007

This paper presents the development of a new type of pseudo‐dynamic test system, in which a conventional static jack is utilized for loading. Two of the new hardware devices developed for the system are detailed: a hydraulic pump system that can adjust the rate of oil flow using an inverter motor, and a controller that controls the jack's motion with a displacement feedback signal transmitted from a digital displacement transducer. The unique advantages of the system are summarized as: larger force capacity achieved by the static jack, maximum use of hardware devices available in many existing structural testing laboratories, and flexibility for program development accomplished by separating tasks into multiple PCs. The reliability of the system is calibrated first by a pseudo‐dynamic test for an SDOF system and then by a pseudo‐dynamic test for a ten‐storey building model having hysteretic dampers. For the latter test, substructuring techniques have been incorporated. The accuracy of the results obtained is discussed based upon the capacity of the system to control displacement and comparison with numerical results.
Non‐destructive damage evaluation of a structure from limited modal parameters
Authors: Topole Klaus Gregor , Stubbs Norris
Published: April 2007

A method to predict structural damage in its location and severity from modal characteristics of the damaged structure is proposed. No a priori knowledge of the modal characteristics of a corresponding baseline structure is required in the proposed formulation. Instead, information on the geometry of the structure which is reflected in its mass and stiffness distribution is needed. From matrix structural analysis, a system of equations is generated which relates the relative change of stiffness of structural members to a load vector generated from modal parameters of the damaged structure. Different solution techniques are suggested to determine the damage from the generated equations. The feasibility of the proposed formulation is demonstrated via a numerical example of a 10‐storey building. Further, an error investigation on the error in the damage predictions due to uncertainties in the input data is carried out.
Earthquake analysis of arch dams including dam‐water‐foundation rock interaction
Authors: Tan Hanchen , Chopra Anil K.
Published: April 2007

The available substructure method and computer program for the earthquake response analysis of arch dams, including the effects of dam‐water interaction, reservoir boundary absorption, and foundation rock flexibility, is extended to include the effects of dam‐foundation rock interaction with inertia and damping of the foundation rock considered. Efficient techniques are developed for evaluating the foundation impedance terms, computationally the most demanding part of the procedure.
Inelastic design spectra accounting for soil conditions
Authors: Riddell Rafael
Published: April 2007

This paper is concerned with the effect of soil conditions on the response of single‐degree‐of‐freedom inelastic systems subjected to earthquake motions. The ground motions considered are 72 horizontal components of motion, most of them recorded during the 3 March, 1985 Chile earthquake (Ms = 7·8) and two main aftershocks; among these records are some of the strongest and longer duration earthquake motions ever recorded. The recording station sites were classified in one of three soil types, which can be generically referred to as rock, firm ground, and medium stiffness soil. Response results for each group were analysed statistically to obtain factors for deriving inelastic design spectra of the Newmark‐Hall type, as well as alternative simplified spectral shapes suitable for code formulation. Particular attention was given to the response modification factors (R) that are commonly used in seismic codes to reduce the ordinates of the elastic spectrum to account for the energy dissipation capacity of the structure. The response modification factors, known to be function of both the natural period of vibration and the ductility factor, are found to be dependent on soil conditions, particularly in the case of medium stiffness soils. It is also shown that the indirect procedure of applying R to the elastic design spectrum is less accurate than directly using functions that represent the inelastic design spectrum.
Rapid essential oil screening of Rosmarinus officinalis L. by hydrodistillation–headspace solvent microextraction
Authors: Salehi Peyman , Fakhari Ali Reza , Ebrahimi Samad Nejad , Heydari Rouhollah
Published: April 2007

The hydrodistillation–headspace solvent microextraction (HD–HSME) method was used for preconcentration and identification of the chemical composition of the essential oil of Rosmarinus officinalis L. The effect of extraction solvent, sample mass, microdrop volume and extraction time on HD–HSME efficiency were investigated and optimized. Four solvents were tested; n‐heptadecane was finally chosen as the extraction solvent and n‐hexadecane was employed as the internal standard. Two methods (hot and cold) were studied for HD–HSME and compared with hydrodistillation as the reference method. The cold method was found to be superior to the hot method. Thirty‐two compounds were identified, of which α‐pinene (48.7%), camphene (13.7%), 1,8‐cineole (13.7%), myrcene (4.5%) and camphor (2.7%) were found to be the major constituents. The results were in good correlation with those obtained by the hydrodistillation method. Copyright © 2007 John Wiley & Sons, Ltd.
Chemical composition and antibacterial activity of the essential oil of Michelia foveolata Merryll ex Dandy from Vietnam
Authors: Lesueur Dominique , Serra Dominique de Rocca , Bighelli Ange , Hoi Tran Minh , Ban Ninh Khac , Thai Tran Huy , Casanova Joseph
Published: April 2007

The chemical composition of the volatile oil extracted from aerial parts (twigs, leaves and flowers) of Michelia foveolata growing wild in Vietnam was investigated by combination of column chromatography, GC (retention indices), GC–MS and 13C‐NMR spectroscopy. Fifty‐eight components were identified, with sabinene (32.4%) and terpinen‐4‐ol (13.7%) as the main constituents. The essential oil was tested against 11 bacteria using the agar disc diffusion method, and exhibited a significant antibacterial activity against Salmonella enterica, Staphylococcus epidermidis, Staphylococcus aureus and Bacillus cereus (MICs = 2–4 µl/ml). Copyright © 2007 John Wiley & Sons, Ltd.
Is central neck dissection necessary for the treatment of lateral cervical nodal recurrence of papillary thyroid carcinoma?
Authors: Roh Jong‐Lyel , Park Jae‐Yong , Rha Ki Sang , Park Chan Il
Published: April 2007

Background:

Although the pattern of cervical lymph node metastases from papillary thyroid carcinoma (PTC) has been described, little is known about the pattern of lateral cervical nodal recurrence. The aim of this study was to establish the optimal strategy for neck dissection in patients who underwent reoperation for lateral cervical recurrence of PTC.

Methods:

We reviewed the records of 22 patients who underwent neck dissection for lateral nodal recurrence of thyroid cancer between 2002 and 2004. Eight patients had thyroid remnants or recurrent tumors in the bed and 6 had undergone lateral neck dissection prior to referral. Patients underwent comprehensive dissection of the posterolateral and ipsilateral (n = 10) or bilateral (n = 12) central neck. The pattern of nodal recurrence and postoperative morbidity were analyzed.

Results:

All patients had lateral compartment involvement, 91% at mid‐lower, 45% at upper, and 18% at posterior sites. Central nodes were involved in 86% of patients: 82% at ipsilateral paratracheal, 32% at pretracheal, 27% at superior mediastinal, and 2 patients at contralateral sites. Skip lateral recurrence with no positive central nodes was rarely observed (14%). Postoperative vocal cord palsy (n = 1) and hypoparathyroidism (n = 5) developed only in patients undergoing bilateral central compartment dissection.

Conclusions:

The inclusion of comprehensive ipsilateral central and lateral neck dissection in the reoperation for patients with lateral neck recurrence of PTC is an optimal surgical strategy. © 2007 Wiley Periodicals, Inc. Head Neck, 2007
Studies on the cell treatment conditions to elicit lipolytic responses from 3T3‐L1 adipocytes to TCDD, 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin
Authors: Li Wen , Vogel Christoph F.A. , Matsumura Fumio
Published: April 2007

Wasting syndrome is one of the hallmark symptoms of poisoning by TCDD (=dioxin), which is associated with the massive loss of adipose tissue and serum hyperlipidemia in vivo. Yet, the most widely used in vitro cell model 3T3‐L1 adipocyte has not been useful for studying such an action of TCDD because of the difficulty of inducing their mature adipocytes to respond to TCDD to go through lipolysis. Here, we made efforts to find the right cell culture and treatment conditions to induce mature 3T3‐L1 adipocytes to go through lipolysis, which is defined as events leading to reduction of lipids in adipocytes. The optimum condition was found to require 7‐day differentiated adipocytes being subjected to DMEM medium containing TCDD (but without insulin) for 5 day incubation with two medium changes (the same composition) on incubation days 2 and 4. After 24 h, the early effect of TCDD on adipocytes was predominantly on inflammation, particularly induction of COX‐2 and KC (IL‐8), which is accompanied by upregulation of C/EBPβ and δ. The sign of TCDD‐induced lipolysis starts slowly and by incubation day 3, a few markers showed modestly significant changes. By day 5 of incubation, however, many markers show highly significant signs of lipolytic changes. Although this process could take place without exogenous macrophages or their cytokines, addition of exogenous TNFα considerably synergized this action of TCDD. In conclusion, under a right condition, 3T3‐L1 adipocytes were found to respond to TCDD to go through lipolysis. The early trigger of such a response appears to be activation of COX‐2, which is amplified by TNFα. J. Cell. Biochem. 102: 389–402, 2007. © 2007 Wiley‐Liss, Inc.
A role for Tbx2 in the regulation of the α2(1) collagen gene in human fibroblasts
Authors: Teng Huajian , Davis Emily , Abrahams Amaal , Mowla Shaheen , Parker M. Iqbal , Prince Sharon
Published: April 2007

The T‐box gene family encodes highly conserved transcription factors that play important roles in embryonic development and have been implicated in carcinogenesis. One member of the family, Tbx2, is generally regarded as a transcriptional repressor but appears to be capable of functioning as an activator depending on the cellular context. This study shows that Tbx2 is expressed in normal human fibroblasts but is drastically reduced in several transformed fibroblast cell lines. This pattern of Tbx2 expression correlated with that observed for the human α2(1) collagen gene (COL1A2). Interestingly, stable expression of transfected Tbx2 in transformed fibroblast cell lines further reduces expression of the human endogenous COL1A2 gene. This ability of Tbx2 to repress the human COL1A2 gene was confirmed in luciferase reporter assays and shown to be independent of the consensus T‐box binding element. J. Cell. Biochem. 102: 618–625, 2007. © 2007 Wiley‐Liss, Inc.
In vitro corrosion behaviour of Ti‐5Al‐2Nb‐1Ta alloy in Hanks solution
Authors: Tamilselvi S. , Rajendran N.
Published: April 2007

Electrochemical polarization and impedance spectroscopic (EIS) techniques were used to investigate the corrosion behavior of Ti‐5Al‐2Nb‐1Ta alloy in Hanks solution at different immersion periods (0 h, 120 h, 240 h and 360 h). The impedance spectra are fitted using a non‐linear least square (NLLS) fitting procedure. The EIS spectra exhibited a two time constant system, suggesting the formation of two layers on the metal surface. The surface morphology of the alloy has been characterized by SEM and EDAX measurements.
Research on corrosivity of narrow distillate oil of crude oil with naphthenic acid and sulfur
Authors: Wang J.H. , Zhao W.Z.
Published: April 2007

The present study is focused on corrosion of crude oil containing naphthenic acid (NA) and sulfur to provide effective anticorrosion measures for the process units of oil refineries. Corrosion laws of distillate oils from crude oil with NA and sulfur can be studied through the impact of temperature, flow velocity, sulfur content, and acid value on corrosion changes of sulfur and NA before and after the experiments.
Refinement of cardiac NMR imaging in awake hamsters: proof of feasibility and characterization of cardiomyopathy
Authors: Parzy Elodie , Fromes Yves , Thiaudiere Eric , Carlier Pierre G.
Published: April 2007

The goal of this study was to demonstrate the feasibility of cardiac NMR imaging in conscious hamsters and its usefulness in evaluating cardiac abnormalities in a small‐animal model of cardiomyopathy. Awake hamsters, controls and cardiomyopathic ones (CHF 147), were immobilized in a dedicated holder. Half‐Fourier single‐shot FSE imaging, with outer‐volume suppression and ‘black‐blood’ contrast provided images free from motion artifact with good visualization of cardiac anatomy at any point in the cardiac cycle. Series of double‐oblique views were acquired with or without electrocardiograph gating. Image acquisition time was 55 ms, with an in‐plane resolution of 470 × 625 µm2. Left ventricular volumes, ejection fraction, and myocardium NMR signal heterogeneity were compared in CHF 147 and control hearts. Left ventricles of CHF 147 hamsters were dilated, as indicated by the increase in end‐diastolic cavity volume (299 ± 79 mm3) compared with the controls (141 ± 39 mm3; P = 0.0002). Left ventricular ejection fraction was largely reduced (45 ± 9% vs 86 ± 4%; P < 0.0001). The NMR signal distribution at an effective echo time of 41 ms was more heterogeneous in the myocardial wall of CHF 147 hamsters than in controls (1.87 ± 0.37 a.u. vs 0.98 ± 0.12 a.u., respectively; P = 0.0002). This study is a refinement of animal experimentation, as it demonstrates for the first time that characteristic features of cardiac pathology can be evaluated with ultra‐fast NMR imaging in conscious small rodents. Copyright © 2007 John Wiley & Sons, Ltd.
Finite elements with embedded strong discontinuities for the modeling of failure in solids
Authors: Linder C. , Armero F.
Published: April 2007

This paper presents new finite elements that incorporate strong discontinuities with linear interpolations of the displacement jumps for the modeling of failure in solids. The cases of interest are characterized by a localized cohesive law along a propagating discontinuity (e.g. a crack), with this propagation occurring in a general finite element mesh without remeshing. Plane problems are considered in the infinitesimal deformation range. The new elements are constructed by enhancing the strains of existing finite elements (including general displacement based, mixed, assumed and enhanced strain elements) with a series of strain modes that depend on the proper enhanced parameters local to the element. These strain modes are designed by identifying the strain fields to be captured exactly, including the rigid body motions of the two parts of a splitting element for a fully softened discontinuity, and the relative stretching of these parts for a linear tangential sliding of the discontinuity. This procedure accounts for the discrete kinematics of the underlying finite element and assures the lack of stress locking in general quadrilateral elements for linearly separating discontinuities, that is, spurious transfers of stresses through the discontinuity are avoided. The equations for the enhanced parameters are constructed by imposing the local equilibrium between the stresses in the bulk of the element and the tractions driving the aforementioned cohesive law, with the proper equilibrium operators to account for the linear kinematics of the discontinuity. Given the locality of all these considerations, the enhanced parameters can be eliminated by their static condensation at the element level, resulting in an efficient implementation of the resulting methods and involving minor modifications of an existing finite element code. A series of numerical tests and more general representative numerical simulations are presented to illustrate the performance of the new elements. Copyright © 2007 John Wiley & Sons, Ltd.
A p‐hierarchical adaptive procedure for the scaled boundary finite element method
Authors: Vu Thu Hang , Deeks Andrew J.
Published: April 2007

This paper describes a p‐hierarchical adaptive procedure based on minimizing the classical energy norm for the scaled boundary finite element method. The reference solution, which is the solution of the fine mesh formed by uniformly refining the current mesh element‐wise one order higher, is used to represent the unknown exact solution. The optimum mesh is assumed to be obtained when each element contributes equally to the global error. The refinement criteria and the energy norm‐based error estimator are described and formulated for the scaled boundary finite element method. The effectivity index is derived and used to examine quality of the proposed error estimator. An algorithm for implementing the proposed p‐hierarchical adaptive procedure is developed. Numerical studies are performed on various bounded domain and unbounded domain problems. The results reflect a number of key points. Higher‐order elements are shown to be highly efficient. The effectivity index indicates that the proposed error estimator based on the classical energy norm works effectively and that the reference solution employed is a high‐quality approximation of the exact solution. The proposed p‐hierarchical adaptive strategy works efficiently. Copyright © 2007 John Wiley & Sons, Ltd.