bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimal weight absorber designs for vibrating structures exposed to random excitations
Authors: Lee Jimmy 
Published: April 2007

AbstractOptimal mass ratios that minimize the response of a laminated beam with an attached absorber are tabulated for various values of beam damping. The beam is treated as an equivalent one degree of freedom (1DOF) main system vibrating in the fundamental mode. The beam is subjected to Gaussian white noise force and Gaussian white noise base frame acceleration. Optimal absorber frequency ratios and absorber damping ratios have been tabulated by others; the results for the classical 1DOF main system with attached absorber suggest that the optimized non‐dimensional response decreases monotonically as the mass ratio increases. However, to generalize this monotonic relation may lead to inappropriate conclusions. If we define a constraint such that an increase in absorber mass leads to a proportional decrease in available beam construction material, i.e. effectively the combined mass of the beam and absorber is minimized, then variations in the mass ratio will affect the beam's parameters such as mass, stiffness and damping. Since some of these parameters are used for non‐dimensionalising the response, inspection of non‐dimensional responses may in some cases lead to inappropriate conclusions. This paper shows the optimal mass ratios for minimizing the response of a structure exposed to earthquake or fluid flow type random excitations.
Effect of random material variability on seismic design parameters of steel frames
Authors: Elnashai A. S. , Chryssanthopoulos M. 
Published: April 2007

AbstractWhereas an increase in material yield stress beyond the code specified characteristic value enhances plastic capacity, it may cause a reduction in overall ductility and energy absorption capability of steel frames. Since quality control of various shapes of sections used on site is difficult to impose, the effect of this random variability on design response parameters should be accounted for in earthquake‐resistant regulations. Moreover, the required weak‐beam/strong‐column design principle in particular, and failure mode control in general, could be undermined if the yield stresses in beam and column assume two opposite extremes in a random sample. This paper addresses the problem of defining the expected range of response parameters in a steel frame with randomly varying yield stress. A simple portal frame is designed using code specified characteristic values and verified by non‐linear transient dynamic analysis. The influence of yield stress variability, including the degree of correlation between beam and column material properties, on several response parameters is assessed through a Monte Carlo simulation study. Results are presented from both univariate and bivariate statistical analyses that quantify the relationship between input (material) and output (response) parameters. Assessment of the interdependence of output parameters given a particular model for yield stress variability is also undertaken. It is shown that certain response parameters exhibit more favourable statistical properties than others. Thus, the implications for seismic code design are discussed in the light of these results.
Seismic‐response‐controlled structure with active mass driver system. Part 2: Verification
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.1 This system has been introduced to an actual ten‐storey office building constructed in Tokyo in August, 1989. The proposed analytical methods utilize circuits of the system and mechanical characteristics to understand the real control effect of the system. Simulation analyses are also performed to verify the analytical model and the control effect during observed earthquakes.
Analytical prediction of the collapse earthquake for R/C buildings: Suggested methodology
Authors: Kappos Andreas J. 
Published: April 2007

AbstractCriteria to be used for the analytical prediction of collapse of R/C buildings subjected to earthquake excitation are suggested. It is attempted to include in the criteria as many of the parameters involved as possible, while keeping the complexity, as well as the cost of analysis reasonably low. Two combined collapse criteria are finally suggested, corresponding to member failure and storey failure. Using these criteria, quantitative estimations can be obtained of the actual values of behaviour factors (q‐factors) used in modern seismic codes. The ground motion dependence of these factors, as well as the sensitivity of their calculated values to the assumption made about the stiffness of R/C members, is illustrated with reference to two typical structures.
Seismic response of a long span cable
Authors: Rao G. Visweswara , Iyengar R. N. 
Published: April 2007

AbstractThe dynamic response of a single span cable due to a travelling seismic excitation is studied in this paper. The influence of propagation time between the supports is investigated in detail. The importance of considering both vertical and longitudinal equations of motion in the analysis is highlighted. The results indicate the considerable influence of the time‐lagged support motions on the cable dynamic tension. A modal combination rule based on the response spectrum method is developed to arrive at the peak estimates of the cable response. Some significant aspects of cable behaviour, especially under horizontal support motion, are discussed.
Results and analysis of soil‐structure interaction experiments performed in the centrifuge
Authors: Weissman Karen , Prevost Jean H. 
Published: April 2007

AbstractIn this paper a centrifuge model that is capable of realistically representing soil‐structure systems subjected to earthquake‐like excitation is used to create a data pool which demonstrates the influence of (i) the frequencies of the structure, (ii) the foundation embedment and (iii) the foundation shape on radiation damping and soil‐structure interaction effects for a structure on a semi‐infinite soil layer over bedrock. The centrifuge model used in this study was developed and validated by the authors in an earlier publication,1 and employs an internal method of earthquake simulation, and the clay‐like material, Duxseal, to absorb wave reflections at the boundary of the soil sample. The results of the experimental study are used to compute damping and stiffness values of a two‐degree‐of‐freedom piecewise‐linear numerical model of the soil‐structure systems. The experimental parameter values are then compared to the values computed using classical text book formulae. The analysis demonstrates the value of the experimental data in validating and developing soil‐structure interaction theory, and confirms the accuracy of classical text book formulae in the linear range.
An incremental mode‐superposition for non‐linear dynamic analysis
Authors: Mohraz Bijan , Elghadamsi Fawzi E. , Chang Chi‐Jen 
Published: April 2007

AbstractThis paper uses an incremental mode‐superposition procedure to compute the inelastic dynamic response of multi‐degree‐of‐freedom systems. A damping matrix proportional to the instantaneous properties is used throughout the analysis. The non‐linear response of several shear type plane and space frames with elastic‐plastic and bilinear column properties subjected to ground excitation was computed by both the incremental mode‐superposition and the direct integration of the coupled equations of motion. When all modes are considered, the responses computed by the incremental mode‐superposition are identical to those from the direct integration. Fewer modes can also be used to compute the response with reasonable accuracy by performing the modal truncation for each time increment.The study shows that incorporating instantaneous damping in non‐linear dynamic analysis is relatively simple and requires less computational time than the direct integration.
Implicit time integration for pseudodynamic tests
Authors: Shing Pui‐Shum B. , Vannan Mani T. , Cater Edward 
Published: April 2007

AbstractThe use of unconditionally stable implicit time integration techniques for pseudodynamic tests has been recently proposed and advanced by several researchers. Inspired by such developments, a pseudodynamic test scheme based on an unconditionally stable implicit time integration algorithm and dual displacement control is presented in this paper. The accuracy of the proposed scheme is proved with error‐propagation analysis. It is shown by numerical examples and verification tests that the error‐correction method incorporated can eliminate the spurious higher‐mode response, which can often be excited by experimental errors. The practicality of the proposed scheme lies in the fact that the implementation is as easy as that of explicit schemes and that the convergence criteria required are compatible with the accuracy limits of ordinary test apparatus.
Magnitude reassessment of New Zealand earthquakes
Authors: Dowrick David J. 
Published: April 2007

AbstractThe surface‐wave magnitudes of a selection of New Zealand earthquakes have been determined on a consistent basis using the ‘Prague formula’ and station corrections. The earthquakes range in magnitude from about 5 to 7.8, covering the instrumental period 1901–1988. Magnitudes for many of the earlier events had not been properly determined previously; and some significant discrepancies from the traditional magnitudes were found.The use of European station data (160° < D < 175°) is important to New Zealand because of its geographical isolation. These distant data were found to give consistently slightly higher Ms than closer stations, but could be used without bias through the station correction procedure. The relationship between Ms and ML was found for 31 ‘shallow’ New Zealand events and much of the scatter was explained as a function of depth. Significant differences in Ms/ML expressions from Europe and California were also found.The limited New Zealand data for Mw and M0 related well to Californian and global relationships with Ms.
Shaking table study of concrete gravity dam monoliths
Authors: Donlon William P. , Hall John F. 
Published: April 2007

AbstractA series of shaking table tests was performed on three small‐scale models of a monolith of a concrete gravity dam in order to simulate earthquake shaking. The purpose of the tests was to examine the nature of crack formation in a gravity dam and the stability of the dam in the presence of cracks. No failures occurred even though the levels of shaking employed were unrealistically high. The good performance owed to the development of crack profiles which had favourable orientations to resist sliding failures in each case. However, the development of an unfavourable crack profile, which cannot be ruled out, and the possibility of water intrusion into open cracks, something not included in the experiments, could lead to failure under significantly lower levels of excitation than those employed.
Effects of sedimentary material on the response of concrete gravity dams
Authors: Bougacha Samir , Tassoulas John L. 
Published: April 2007

AbstractThe transient response of a concrete gravity dam to a selected earthquake record is determined in order to evaluate the significance of the sedimentary material accumulating on the bottom of the reservoir. The sediment is modelled as a two‐phase medium (fluid‐filled, poroelastic solid), and the analysis is carried out accounting for all interactions between system components (dam, water, sediment, foundation).
A post‐correction integration algorithm for non‐linear dynamic analysis of structures
Authors: And Keming Sun , Pires José A. , Tao Jian Ren 
Published: April 2007

AbstractA simple and practical post‐correction direct integration approach to compute the dynamic response of structures with non‐linear stiffness properties is introduced. This approach is based on the assumption that the effect of a non‐linear restoring force is equivalent to a series of impulse functions acting on the so called fundamental linear system. Applying this basic idea with unconditionally stable step‐by‐step integration methods, the non‐linear dynamic analysis of structures can be executed by a linear one‐step direct integration procedure by modifying the velocity and acceleration at the end of the time step (post‐correction) instead of modifying the structural properties at the beginning of each time step. A general description of the proposed post‐correction approach for the direct integration of the equations of motion is presented. The algorithm to combine the proposed approach with the unconditionally stable Wilson θ method is discussed in great detail. Numerical results are included to verify the accuracy of the method and to illustrate the computing procedure.
Dynamic characteristics of non‐classically damped structures
Authors: Xu Kangming , Igusa Takeru 
Published: April 2007

AbstractThe equations of motion of a structure in undamped modal coordinates may have non‐zero off‐diagonal terms in the damping matrix. Although these terms are commonly neglected, studies have shown that they may have a significant influence on the response to dynamic loads. In this paper, two independent criteria are developed to determine when these damping terms will affect the structure's modal properties and response. It is found that even small off‐diagonal damping values can be significant if the structure has closely spaced natural frequencies. To quantify and understand the influence of these damping terms, closed‐form analytical expressions are derived for the modal properties and harmonic and stochastic response of structures with closely spaced natural frequencies. One conclusion is that off‐diagonal damping terms will decrease a modal damping ratio for each pair of closely spaced modes. This is significant, since a response analysis performed by neglecting these off‐diagonal terms will underestimate the true response.
Stochastic response of combined primary‐secondary structures under seismic input
Authors: Falsone G. , Muscolino G. , Ricciardi G. 
Published: April 2007

AbstractA technique for non‐stationary stochastic analysis of linear combined primary and secondary subsystems subjected to a zero‐mean Gaussian base excitation is presented. The proposed technique, based on the use of the Taylor's expansion in evaluating the operators which appear in the step‐by‐step procedure, does not require the evaluation of the complex eigenproperties of the combined system. Operating in this way, even though the numerical procedure is a conditionally stable one, appears to be more efficient than existing methods to evaluate the dynamic response of such composite systems. It is also shown that the proposed procedure is available whether the seismic input is idealized as a filtered white noise or it is defined by means of its autocorrelation function.
The non‐linear response of unreinforced masonry buildings to earthquake excitations
Authors: Kamil Tanrikulu A. , Mengi Yalcin , McNiven Hugh D. 
Published: April 2007

AbstractThe three‐dimensional non‐linear earthquake behaviour of unreinforced masonry buildings is studied by using a constitutive model established experimentally for burned‐clay brick masonry wall panels. The parameter functions appearing in the constitutive model are modified so that they accommodate a wall panel made of a general masonry material. In the study it is assumed that the floors of the masonry building are reinforced concrete slabs which are infinitely rigid in their own planes and that the wall panels possess only in‐plane rigidities. Some examples involving earthquake analyses of two different masonry structures are presented. It is found that the predictions of the model used in the study are in harmony with the experimental data available in the literature.
A two‐stage epidemiologic study on prevalence of eating disorders in female university students in Mexico
Authors: Mancilla‐Diaz Juan Manuel , Franco‐Paredes Karina , Vazquez‐Arevalo Rosalia , Lopez‐Aguilar Xochitl , Alvarez‐Rayon Georgina L. , Tellez‐Giron Ma. Trinidad O. 
Published: April 2007

AbstractObjectiveThis study investigated the prevalence of eating disorders (ED) in women.MethodTwo samples of university students (1995, n = 522; 2002, n = 880) completed the Eating Attitudes Test and the Bulimia Test (BULIT; Stage 1). During Stage 2, the women that exceeded the cut‐off point of one or both questionnaires and a random sample of women that did not exceed the cut‐off point were interviewed.ResultsThe results showed a prevalence rate of 0.49% for ED in 1995 (0.14% for bulimia nervosa [BN] and 0.35% for EDs not otherwise specified [EDNOS]) and a prevalence rate of ED of 1.15% in 2002 (0.24% for BN and 0.91% for EDNOS). Anorexia nervosa was not found in either of the evaluated periods. Nevertheless, the results must be taken with reservation since there was a high rate of loss to follow‐up (second stage).DiscussionThe data of this study support the findings of other studies, including studies with Spanish‐speaking samples, that EDNOS is the most common ED followed by BN and AN. Copyright © 2007 John Wiley & Sons, Ltd and Eating Disorders Association.
A Direct Borohydride/Hydrogen Peroxide Fuel Cell with Reduced Alkali Crossover
Authors: Raman R. K. , Shukla A. K. 
Published: April 2007

AbstractA direct borohydride/hydrogen peroxide fuel cell, employing a misch‐metal alloy anode and carbon‐supported lead sulfate (PbSO4/C) cathode with a Nafion®‐961 membrane electrolyte, is reported. The use of a Nafion®‐961 membrane electrolyte in the fuel cell lessens the crossover of aqueous sodium hydroxide from the anode to cathode. Initial results indicate that the fuel cell exhibits a maximum power density of 10 mW cm–2 at an operating voltage of 0.77 V with an oxidant utilization of about 80% at 25 °C. The fuel cell also avoids the use of noble‐metal catalysts. The unique combination of sodium borohydride and hydrogen peroxide, both of which are in aqueous from, paves the way for a convenient unitized refueling design that is inherently compact compared to fuel cells that use gaseous reactants. Such a fuel cell is expected to find application in situations where anaerobic conditions prevail, e.g., in submersible and space applications.
Redox Cycling of Ni‐Based Solid Oxide Fuel Cell Anodes: A Review
Authors: Sarantaridis D. , Atkinson A. 
Published: April 2007

AbstractThe published literature relating to damage to SOFCs caused by redox cycling of Ni‐based anodes is reviewed. The review covers the kinetics of Ni oxidation and NiO reduction (as single phases and as constituents of composites with yttria‐stabilised zirconia, YSZ), the dimensional changes associated with redox cycling and the effect of this on the mechanical integrity and electrical performance of cells and stacks. A critical parameter is the expansion strain that is caused by oxidation. Several studies report that the first complete oxidation of a Ni/YSZ composite causes a linear expansion of the order of 1%, but the actual values vary substantially between different investigations. The oxidation strain is the result of microstructural irreversibility during the redox process and leads to strain accumulation over several redox cycles. This can cause mechanical disruption to an anode, anode support or other cell components attached to the anode.A simplified mechanical model of the stress and damage that are likely to be caused by anode expansion is proposed and applied to anode‐supported, electrolyte‐supported and inert substrate‐supported cell configurations. This allows the maximum oxidation strain to avoid damage in each configuration to be estimated.
Care‐giver advice as a preventive measure for drinking during pregnancy: zeros, categorical outcome responses, and endogeneity
Authors: Terza Joseph V. , Kenkel Donald S. , Lin Tsui‐Fang , Sakata Shinichi 
Published: April 2007

AbstractWe conduct an empirical investigation of the impact of prenatal care‐giver advice on alcohol consumption by pregnant women. In the design of the model and estimator, we pay particular attention to three aspects of the data. First, a large proportion of pregnant women do not drink at all. To accommodate this aspect of the sample we base the essential formulation of the model on the modified version of the two‐part approach of Duan et al. (Journal of Business and Economic Statistics 1983; 1: 115–126.) suggested by Mullahy (Journal of Health Economics 1998; 17: 247–281.). Second, in the survey that we analyze (the 1988 National Maternal and Infant Health Survey – NMIHS), respondents were only required to report their consumption up to a specified range of values (e.g. 1–2 drinks per week, 2–5 drinks per week, and so on). For this reason, the model is cast in the grouped regression framework of Stewart (Review of Economic Studies 1983; 50: 141–149.). Third, the binary physician advice variable is likely to be endogenous and the econometric specification explicitly accounts for this possibility. To summarize the results, we find that failing to account for endogeneity leads to the counterintuitive conclusion that advice has a positive and statistically significant influence on drinking during pregnancy. When the model is extended to allow for potential endogeneity, we find that advice has a negative and statistically significant impact. Copyright © 2007 John Wiley & Sons, Ltd.
High and low dosage oxcarbazepine versus naltrexone for the prevention of relapse in alcohol‐dependent patients
Authors: Martinotti G. , Di Nicola M. , Romanelli R. , Andreoli S. , Pozzi G. , Moroni N. , Janiri L. 
Published: April 2007

AbstractIntroductionOxcarbazepine (OXC) reduces high‐voltage‐activated calcium currents, thus reducing glutamatergic transmission at corticostriatal synapses. This effect on NMDA glutamatergic transmission may play a role against the increased glutamatergic transmission determined by alcohol withdrawal. To investigate the efficacy and safety of OXC in relapse prevention we compared OXC at different dosages with Naltrexone (NAL) in a 90 days randomised open‐label trial. Craving and psychiatric symptoms improvements were the secondary endpoints.MethodsEighty‐four detoxified alcohol dependent subjects currently meeting clinical criteria for alcohol dependence were randomised into three groups: 27 patients received 50 mg of naltrexone, 29 received 1500–1800 mg of oxcarbazepine (OXC high), 28 patients 600–900 mg of oxcarbazepine (OXC low). Craving (VAS; OCDS) and withdrawal (AWRS) rating scales were applied; psychiatric symptoms were evaluated through the SCL‐90‐R.ResultsA significantly larger number of subjects remained alcohol free in the OXC high group (58.6%) with respect to both the OXC low (42.8%) and the NAL groups (40.7%). Comparing the OCDS total scores at the end of the treatment, the improvement was significantly greater for the NAL group with respect to the OXC low group. The reduction of the Hostility‐Aggression subscore of the SCL‐90‐R was significantly greater in the OXC high group than that of the other groups. Dual diagnosis patients had a better outcome when treated with OXC high.DiscussionOXC at a dosage of 1500–1800 mg/day might be beneficial in terms of alcohol relapse prevention. The low dosage formulation did not show the same trend, but it still remain in the same range as NAL. The mechanism involved in the efficacy of oxcarbazepine in relapse prevention could be less related to craving and more connected to the treatment of the comorbid psychiatric symptomatology and the alcohol protracted withdrawal syndrome. Copyright © 2007 John Wiley & Sons, Ltd.