bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrete models for vertical vibrations of surface and embedded foundations
Authors: De Barros Francisco C. P. , Luco J. Enrique 
Published: April 2007

AbstractA five‐parameter discrete model that approximates the dynamic force4isplacement relationship for rigid foundations undergoing vertical vibrations on a uniform elastic half‐space is presented. The model involves a combination of two springs, two viscous dampers and a mass. Values of the parameters for circular, square and rectangular foundations placed on the surface or embedded in an elastic half‐space are listed. The parameters are obtained by minimizing the discrepancy between the force4isplacement relation for the model and that obtained by solution of the mixed boundary‐value problem of the rigid foundation on an elastic half‐space. The definition of an appropriate input motion to represent wave excitation is also discussed. The input motion to the discrete model differs from the input motion that should be used in a continuum model.
Response analysis of flexible MDF systems for multiple‐support seismic excitations
Authors: Yamamura Nobumichi , Tanaka Hiroshi 
Published: April 2007

AbstractTwo practical approaches, response spectrum and time‐history methods, are developed to evaluate the response of flexible multi‐degree‐of‐freedom (MDF) systems, notably long‐span bridges, to multiple‐support seismic excitations. For practical convenience, ground motions within a group of adjacent supports on continuous soil or rock are assumed to be uniform and synchronized, while those of different groups are treated as non‐uniform and uncorrelated. The response spectrum analysis is extended to include the cross‐correlation of modal responses, which prove important when closely spaced modal frequencies exist. An example of the significance of multiple‐support excitations is illustrated by application to a suspension bridge. Qualitatively comparable effects can be expected for other bridges of similar type or dimensions.
Solution of viscously damped linear systems using a set of load‐dependent vectors
Authors: Chen Harn C. , Taylor Robert L. 
Published: April 2007

AbstractThis paper considers a solution method for viscously damped linear structural systems which are subjected to transient loading. The equations of motion of such systems are written in a first‐order form. A solution subspace is generated using the damped dynamic matrix and the static deflection from the first‐order form of the equations of motion. Two convenient bases, Lanczos vectors and Ritz vectors, are constructed from this subspace. An approximate solution is then obtained by superposition of the Lanczos vectors or the Ritz vectors. In contrast to the traditional mode superposition method using complex eigenvectors, the Lanczos vectors or the Ritz vectors are less expensive to generate than the complex eigenvectors, yet yield comparable accuracy. In addition, there is no need for a static correction since the static deflection is already contained in our solution subspace. Numerical examples are presented to show the potential of using the Ritz vectors to compute responses of damped dynamic systems.
Seismic damage assessment based on different hysteretic rules
Authors: Loh Chin‐Hsiung , Ho Ri‐Chuan 
Published: April 2007

AbstractThe inelastic response of a single‐degree‐of‐freedom (SDOF) system to different sets of earthquake records was analysed to study the significance of ground motion characteristics on structural damage. Six non‐linear models were used. The ductility ratio and hysteretic energy index were chosen as two important damage indices to measure the structural damage. The dispersion phenomenon exhibited by yield spectra due to input ground motion was reduced by incorporating the ground motion a/v ratio into the two damage indices. Finally, empirical formulae for estimating two measures of structural damage were developed for each hysteretic model.
Random response of a single‐degree‐of‐freedom vibro‐impact system with clearance
Authors: Jing Hung‐Sying , Young Mindhu 
Published: April 2007

AbstractThe closed form solutions of the stationary random response of a single‐degree‐of‐freedom vibro‐impact system with clearance are formulated in this paper. The Hertz contact law from elasticity is used to model the contact phenomena between the mass and constraint during vibration. The excitation is assumed to be a stationary white Gaussian process with zero mean. Through solving the time‐independent Fokker‐Planck equation, the stationary responses are obtained analytically. The effects of contact stiffness and clearance on the response are discussed probabilistically. It is found that, when the clearance is about twice the square root of the mean square response of the corresponding linear system, the contact phenomena are almost negligible.
How to model amplification of strong earthquake motions by local soil and geologic site conditions
Authors: Trifunac Mihailo D. 
Published: April 2007

AbstractA simple equation is proposed to describe the physical nature of the frequency dependent amplification of strong earthquake shaking by local soil and geologic site conditions. For high frequencies, the amplification effects compete with anelastic attenuation. For long periods, along the period axis, the amplification can be described by a low‐pass filter with roll‐off near the period for which the quarter wavelength of wave motion in soil, or in sediments, coincides with their thickness. In the intermediate period range the amplification depends only on the impedance jump between the ‘soft’ surface materials and ‘hard’ basement, and is independent of the thickness of soil or of sedimentary layers.
Inelastic seismic response of one‐storey, asymmetric‐plan systems: Effects of stiffness and strength distribution
Authors: Goel Rakesh K. , Chopra Anil K. 
Published: April 2007

AbstractThe effects of plan‐wise distribution of stiffness and strength‐as determined by the number, location, orientation and yield deformations of resisting elements‐on the inelastic response of one‐storey systems are evaluated. In particular, various systems are investigated for wide ranges of parameters involved, with the objective of establishing how the response is influenced by: (i) the presence of resisting elements perpendicular to the direction of ground motion; (ii) the number of resisting elements along the direction of ground motion; (iii) the overstrength typical of code‐designed buildings; (iv) the relative values of strength and stiffness eccentricities; and (v) whether the asymmetry of the system is due to eccentricity in stiffness or in mass. The results presented for a simple excitation make it possible to explain the inconsistencies in conclusions from various earlier investigations, and to evaluate their applicability to actual buildings.
Seismic‐response‐controlled structure with active mass driver system. Part 1: Design
Authors: Kobori Takuji , Koshika Norihide , Yamada Kazuhiko , Ikeda Yoshiki 
Published: April 2007

AbstractAn Active Mass Driver (AMD) system is proposed to suppress actively the response of a building to irregular external excitations such as earthquakes and typhoons. This system has been introduced to an actual ten‐storey office building for the first time in the world. The system controls the motions of a structure by means of an external energy supply. It consists of an auxiliary mass installed in a building and an actuator that operates the mass and produces a control force which counters disturbances to the building. The design method of the AMD system, including the location of the installation and the capacity and stability of the system, is proposed. Simplification of the control algorithm is also described.
Identification of equivalent structural schemes for coupled systems
Authors: Benedetti D. , Benzoni G. M. 
Published: April 2007

AbstractSome arrays of buildings in historical nuclei of Central Italy are currently monitored by steady‐state accelerometers. The aim is to identify the structural scheme of a single building representing the effect on it of the other systems of the array. A method for interpreting the recorded responses is presented. It is based on the a priori assumption of a scheme for the building of interest, thought of as being isolated, and on the identification of two sets of masses and of stillnesses to add in order to account for the array effect. The method is limited to linear behaviour and to planar systems.
Strong‐motion accelerograph array in Santiago, Chile, and preliminary evaluation of site effects
Authors: Midorikawa Saburoh , Riddell Rafael , Cruz Ernesto 
Published: April 2007

AbstractA strong‐motion accelerograph array in Santiago, Chile has been installed. One of the sites is located on rock and the other six sites are on soil ground with different surface geology, so that local site effects on ground motions can be studied. As a preliminary evaluation of the site effects, the spectral ratios of weak‐motion records at soil sites with respect to the rock site are calculated. The spectral ratios show that the amplification of ground motions with respect to the rock site is approximately 1.25 on dense gravel deposits, 2.5 on stiff pumice ground and 3.5 on soft silt ground.
A unified earthquake‐resistant design method for steel frames using arma models
Authors: Takewaki Izuru , Conte Joel P. , Mahin Stephen A. , Pister Karl S. 
Published: April 2007

AbstractThe objective of this paper is to develop a unified earthquake‐resistant design method for moment‐resisting steel frames, including the design earthquake via a dynamic ARMA model.Important features of this design method are: (i) to make it possible to incorporate inherent uncertain features of design earthquakes into the design process itself through the dynamic ARMA model, (ii) to provide a simplified design formula for a preliminary design of moment‐resisting steel frames based upon the concept of stiffness‐oriented design and (iii) to facilitate the formulation of a new probabilistic multi‐objective optimal design problem aimed at finding the design with the minimum level of designer's dissatisfaction. In this optimal design problem, constraints and objectives are handled in a unified manner after a feasible design is obtained.A design example is presented to demonstrate the validity of this unified design method and to examine the convergence of response statistics. Finally, the generality and practicality of this design method are assessed.
Controlling seismic response of eccentric structures by friction dampers
Authors: Pekau O. A. , Guimond R. 
Published: April 2007

AbstractPrevious studies have demonstrated the good performance of friction dampers in symmetric frame structures subjected to earthquake excitation. This paper examines their effectiveness in asymmetric structures where lateral‐torsional coupling characterizes the behaviour. A parametric study is first performed employing an idealized single‐storey structure; this is followed by the example of a three‐dimensional 5‐storey prototype structure equipped with friction dampers. The parametric results show that it is necessary to tune the friction damped braces with respect to both the stiffness of the braces and the slip load of the devices. For properly tuned structures, maximum response for all magnitudes of eccentricity between the centres of stiffness and mass is reduced to levels equal to or less than that of the corresponding symmetric structure. Compared to this prediction, the prototype structure with friction damped bracing exhibits the desired improvement in performance; namely, the devices slip at all storey levels while the frames remain elastic.
Insights on cutoff frequency for foundation on soil layer
Authors: Meek Jethro W. , Wolf John P. 
Published: April 2007

AbstractIn foundation dynamics a most important effect, often overlooked, is that for a soil layer on rock a cutoff frequency exists, below which there is no radiation damping. Valuable insights into the nature of the cutoff frequency may be obtained without solving differential equations. Physically motivated wave‐propagation techniques enable modification of familiar unbounded cone models to represent layered soil. Echoes corresponding to the natural period of the layer appear to account for the cutoff frequency. The cone models have simple solutions in both the time and frequency domains.An investigation of the simplest system with a cutoff frequency, the shear bar on an elastic foundation, shows that, for radiation to take place, the radius of penetration of waves must extend to infinity. In order to reach infinity, the waves' displacement amplitude must die off in a special way, otherwise conservation of energy would be violated. These considerations reveal a general radiation criterion, namely, that the waves' amplitude must diminish in inverse proportion to the square root of the far‐field boundary surface. Using the radiation criterion, it is possible to derive transmitting boundaries for shear waves which replace the far field.
Modelling of a cable‐stayed bridge for dynamic analysis
Authors: Wilson John C. , Gravelle Wayne 
Published: April 2007

AbstractThe subject of dynamic response of cable‐stayed bridges has received increasing attention in recent years as this type of bridge becomes ever more popular. In most publications on the dynamic behaviour of cable‐stayed bridges, only cursory treatment is given to many of the details of the actual development of a suitable finite element model. This paper provides a detailed description of the development of one class of linear elastic finite element model for the dynamic analysis of a cable‐stayed bridge. The bridge modelled in this study is the Quincy Bayview Bridge in Illinois. The translation of structural data into a form useful for formulation of a three‐dimensional finite element model is presented in some detail, including evaluation of translational and rotational mass and stiffnesses for the deck, modelling of the towers and cables, modelling of the bearings and considerations for accurate geometric representation between the model and the full‐scale structure. In a companion paper, the modal behaviour predicted by the finite element model is compared to measured ambient vibration properties of the full‐scale structure.
Implicit time integration for pseudodynamic tests: Convergence and energy dissipation
Authors: Shing Pui‐Shum B. , Vannan Mani T. 
Published: April 2007

AbstractThe convergence and energy‐dissipation characteristics of an unconditionally stable implicit time integration scheme that has been adopted for pseudodynamic testing are examined in this paper. A convergence criterion is derived for general multiple‐degree‐of‐freedom softening systems. Furthermore, it is shown that undesired loading and unloading cycles can be avoided in numerical iterations by scaling down the incremental corrections. Finally, it is proved that the total energy dissipation introduced by the residual convergence errors and proposed numerical correction is always positive for any softening structures.
A generalization of the timoshenko beam model for coupled vibration analysis of thin‐walled beams
Authors: Capuani D. , Savoia M. , Laudiero F. 
Published: April 2007

AbstractA generalization of the Timoshenko beam model is presented which accounts for the influence of the shear strains, due to non‐uniform bending and torsion, on the flexural‐torsional vibrations of thin‐walled cores with open or closed cross‐section. The axial displacement field incorporates the torsion secondary warping as well as the warping terms depending on the shear resultants. It is shown that exact solutions for the interior domain problem can be obtained under proper load conditions. Moreover, a discrete model for the free‐vibration analysis is derived by adopting a linear interpolation of the unknown functions and a reduced integration in order to avoid locking phenomena. Various applications are developed, including the case of the coupled vibrations of a shear‐core‐steel‐frame building.
A bulk power system reliability assessment methodology
Authors: Yang Fang , Meliopoulos A. P. Sakis , Cokkinides George J. , Stefopoulos George 
Published: April 2007

AbstractThis paper describes a methodology for the reliability evaluation of bulk power systems. The method encompasses the systematic enumeration of contingencies and the evaluation of their effects on the system over a range of system load levels. Contingencies and electric load levels are described with Markov models. Reliability indices are computed using these models. Both an adequacy approach and a simplified security approach are considered in the effects analysis. The overall framework of the proposed methodology is capable of considering the full security approach but it is not addressed in this paper. In the adequacy approach, an improved system simulation method is used based on the single‐phase quadratized power flow (QPF). Remedial actions (RAs) are also applied for the purpose of alleviating system abnormal operating conditions. The adequacy approach determines whether the system is adequate for supplying the electric load without operating constraint violations. In the simplified security approach, the immediate response of the system is of interest. The simulation approach consists of an inertial re‐dispatch and operating conditions immediately after a contingency before any controls take effect. The objective is to determine whether cascading failures occur. The proposed methodology has been applied to two reliability test systems. Copyright © 2007 John Wiley & Sons, Ltd.
Reduced raft‐association of NF155 in active MS‐lesions is accompanied by the disruption of the paranodal junction
Authors: Maier Olaf , Baron Wia , Hoekstra Dick 
Published: April 2007

AbstractNeurofascin155 (NF155) is required for the establishment of the paranodal axo‐glial junction, the predominant interaction site between myelin and axon. It has been shown that the distribution of NF155 is altered in demyelinating diseases such as multiple sclerosis (MS). However, little is known about the biochemical mechanisms underlying these changes. We therefore compared NF155 in postmortem tissue of active and chronic inactive MS lesions with white matter from healthy controls. Although NF155 showed a very similar expression in all control white matter samples, a strong individual variation was observed in MS‐lesions with NF155‐levels reduced in most samples. At the same time an NF155‐fragment was increased in MS‐lesions, suggesting that NF155 is subject to protein degradation in lesion sites. Interestingly, the association of NF155 to membrane microdomains (rafts) was reduced in all lesions, irrespective of the amount of NF155, indicating that membrane association of NF155 was generally affected. Therefore, myelin fractionation experiments were performed to analyze the fate of paranodal proteins during demyelination. Although NF155 was enriched in heavy myelin from both control white matter and active MS‐lesions, association of Caspr1/paranodin with heavy myelin was abolished in MS‐lesions, demonstrating that paranodal junctions are disrupted. In conclusion, the data support the hypothesis that efficient raft‐association of NF155 is essential for the assembly of the paranodal junction and demonstrate that reduced association of NF155 to lipid rafts is accompanied by the disassembly of the paranodal junction and thus contributes to the demyelination process in MS. © 2007 Wiley‐Liss, Inc.
Exploring the clinical and social determinants of prescribing anticholinergic medication for Chinese patients with schizophrenia
Authors: Yu‐Tao Xiang , Yong‐Zhen Weng , Chi‐Ming Leung , Wai‐Kwong Tang , Ungavri Gabor Sandor 
Published: April 2007

AbstractAimsTo‐date few studies have investigated prescription patterns of anticholinergic medication (ACM) in Chinese patients with schizophrenia in general and outpatients in particular. This study examined the frequency and socio‐demographic and clinical correlates of ACM in Hong Kong (HK) and Beijing (BJ), China.MethodsFive hundred and five clinically stable outpatients with schizophrenia were randomly selected and interviewed in HK and BJ using standardized assessment instruments. Basic socio‐demographic and clinical data and psychotropic drug prescriptions were collected at the time of the diagnostic interview.ResultsACM was found in 47.7% of (n = 241) the whole sample and in 54.1 and 41.2% of the HK and BJ samples, respectively. ACM was associated with more frequent use of antipsychotic (AP) polypharmacy, typical AP drugs, and a combination of depot and oral AP, less use of clozapine and atypical and oral AP, a lack of health insurance, higher doses of APs, severity of extrapyramidal side effects (EPS), a higher number of APs prescribed, and study sites. In multiple logistic regression analysis, higher doses of APs, less frequent use of an atypical AP, and study sites all remained significantly associated with ACM.ConclusionAlthough the ethnic and clinical characteristics of the two samples were nearly identical, there was a wide variation in the frequency of ACM prescriptions between HK and BJ suggesting that socio‐cultural and economical factors as well as traditions of psychiatric practice all played a role in determining the use of ACM. Prescribing ACM in neither site was in line with current recommendation. Copyright © 2007 John Wiley & Sons, Ltd.
Effects of smoking marijuana on focal attention and brain blood flow
Authors: O'Leary Daniel S. , Block Robert I. , Koeppel Julie A. , Schultz Susan K. , Magnotta Vincent A. , Ponto Laura Boles , Watkins G. Leonard , Hichwa Richard D. 
Published: April 2007

AbstractUsing an attention task to control cognitive state, we previously found that smoking marijuana changes regional cerebral blood flow (rCBF). The present study measured rCBF during tasks requiring attention to left and right ears in different conditions. Twelve occasional marijuana users (mean age 23.5 years) were imaged with PET using [15O]water after smoking marijuana or placebo cigarettes as they performed a reaction time (RT) baseline task, and a dichotic listening task with attend‐right‐ and attend‐left‐ear instructions. Smoking marijuana, but not placebo, resulted in increased normalized rCBF in orbital frontal cortex, anterior cingulate, temporal pole, insula, and cerebellum. RCBF was reduced in visual and auditory cortices. These changes occurred in all three tasks and replicated our earlier studies. They appear to reflect the direct effects of marijuana on the brain. Smoking marijuana lowered rCBF in auditory cortices compared to placebo but did not alter the normal pattern of attention‐related rCBF asymmetry (i.e., greater rCBF in the temporal lobe contralateral to the direction of attention) that was also observed after placebo. These data indicate that marijuana has dramatic direct effects on rCBF, but causes relatively little change in the normal pattern of task‐related rCBF on this auditory focused attention task. Copyright © 2007 John Wiley & Sons, Ltd.