bluuebunny/crossref_metadata_2025_split huggingface dataset:
Material damping for lumped‐parameter models of foundations
Authors: Meek Jethro W. , Wolf John P. 
Published: April 2007

AbstractIn 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

AbstractIt 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

AbstractAn 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractThis 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

AbstractThis 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

AbstractAnalytical 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

AbstractStudied 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

AbstractThis 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

AbstractA 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

AbstractThe 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractBackground: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

AbstractWasting 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

AbstractThe 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.