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Response Spectra (response + spectrum)

Distribution by Scientific Domains

Engineering	92%
2 Other Domains	8%

Kinds of Response Spectra

elastic response spectrum

Selected Abstracts

Author's Reply to Discussion by George Mylonakis and Costis Syngros of ,Response spectrum of incompatible acceleration, velocity and displacement histories' Earthquake Engng Struct.

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2002

No abstract is available for this article. [source]

Dimensional analysis of the earthquake-induced pounding between adjacent structures

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2009
Elias Dimitrakopoulos
Abstract In this paper the dynamic response of two and three pounding oscillators subjected to pulse-type excitations is revisited with dimensional analysis. Using Buckingham's ,-theorem the number of variables that govern the response of the system is reduced by three. When the response is presented in the dimensionless ,-terms remarkable order emerges. It is shown that regardless of the acceleration level and duration of the pulse all response spectra become self-similar and follow a single master curve. This is true despite the realization of finite duration contacts with increasing durations as the excitation level increases. All physically realizable contacts (impacts, continuous contacts, and detachments) are captured via a linear complementarity approach. The study confirms the existence of three spectral regions. The response of the most flexible among the two oscillators amplifies in the low range of the frequency spectrum (flexible structures); whereas, the response of the most stiff among the two oscillators amplifies at the upper range of the frequency spectrum (stiff structures). Most importantly, the study shows that pounding structures such as colliding buildings or interacting bridge segments may be most vulnerable for excitations with frequencies very different from their natural eigenfrequencies. Finally, by applying the concept of intermediate asymptotics, the study unveils that the dimensionless response of two pounding oscillators follows a scaling law with respect to the mass ratio, or in mathematical terms, that the response exhibits an incomplete self-similarity or self-similarity of the second kind with respect to the mass ratio. Copyright © 2008 John Wiley & Sons, Ltd. [source]

On the reliability of long-period response spectral ordinates from digital accelerograms

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2008
Roberto Paolucci
Abstract Using records from co-located broadband and digital strong motion (SM) instruments, it is first shown that the displacement waveforms obtained by double integration of the accelerogram need not be free of unrealistic baseline drift to yield reliable spectral ordinates up to at least 10,s. Secondly, to provide objective criteria for selecting reliable digital SM records for ground motion predictions at long periods, a set of synthetic accelerograms contaminated by random long-period noise has been used, and the difference between the original accelerograms and the spurious ones in terms of response spectra has been quantified, by introducing a noise index that can be easily calculated based on the velocity waveform of the record. The results of this study suggest that high-pass filtering the digital acceleration record from a cutoff period selected to suppress baseline drifts on the displacement waveform appears to be in most cases too conservative and unduly depletes reliable information on long-period spectral ordinates. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Spectral analysis and design approach for high force-to-volume extrusion damper-based structural energy dissipation

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2008
Geoffrey W. Rodgers
Abstract High force-to-volume extrusion damping devices can offer significant energy dissipation directly in structural connections and significantly reduce seismic response. Realistic force levels up to 400,kN have been obtained experimentally validating this overall concept. This paper develops spectral-based design equations for their application. Response spectra analysis for multiple, probabilistically scaled earthquake suites are used to delineate the response reductions due to added extrusion damping. Representative statistics and damping reduction factors are utilized to characterize the modified response in a form suitable for current performance-based design methods. Multiple equation regression analysis is used to characterize reduction factors in the constant acceleration, constant velocity, and constant displacement regions of the response spectra. With peak device forces of 10% of structural weight, peak damping reduction factors in the constant displacement region of the spectra are approximately 6.5,×, 4.0,×, and 2.8,× for the low, medium, and high suites, respectively. At T,=,1,s, these values are approximately 3.6,×, 1.8,×, and 1.4,×, respectively. The maximum systematic bias introduced by using empirical equations to approximate damping reduction factors in design analyses is within the range of +10 to ,20%. The seismic demand spectrum approach is shown to be conservative across a majority of the spectrum, except for large added damping between T,=,0.8 and 3.5,s, where it slightly underestimates the demand up to a maximum of approximately 10%. Overall, the analysis shows that these devices have significant potential to reduce seismic response and damage at validated prototype device force levels. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Does amplitude scaling of ground motion records result in biased nonlinear structural drift responses?

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2007
Nicolas Luco
Abstract Limitations of the existing earthquake ground motion database lead to scaling of records to obtain seismograms consistent with a ground motion target for structural design and evaluation. In the engineering seismology community, acceptable limits for ,legitimate' scaling vary from one (no scaling allowed) to 10 or more. The concerns expressed by detractors of scaling are mostly based on the knowledge of, for example, differences in ground motion characteristics for different earthquake magnitude,distance (Mw,Rclose) scenarios, and much less on their effects on structures. At the other end of the spectrum, proponents have demonstrated that scaling is not only legitimate but also useful for assessing structural response statistics for Mw,Rclose scenarios. Their studies, however, have not investigated more recent purposes of scaling and have not always drawn conclusions for a wide spectrum of structural vibration periods and strengths. This article investigates whether scaling of records randomly selected from an Mw,Rclose bin (or range) to a target fundamental-mode spectral acceleration (Sa) level introduces bias in the expected nonlinear structural drift response of both single-degree-of-freedom oscillators and one multi-degree-of-freedom building. The bias is quantified relative to unscaled records from the target Mw,Rclose bin that are ,naturally' at the target Sa level. We consider scaling of records from the target Mw,Rclose bin and from other Mw,Rclose bins. The results demonstrate that scaling can indeed introduce a bias that, for the most part, can be explained by differences between the elastic response spectra of the scaled versus unscaled records. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Scaling of spectral displacement ordinates with damping ratios

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2005
Julian J. Bommer
Abstract The next generation of seismic design codes, especially those adopting the framework of performance-based design, will include the option of design based on displacements rather than forces. For direct displacement-based design using the substitute structure approach, the spectral ordinates of displacement need to be specified for a wide range of response periods and for several levels of damping. The code displacement spectra for damping values higher than the nominal value of 5% of critical will generally be obtained, as is the case in Eurocode 8 and other design codes, by applying scaling factors to the 5% damped ordinates. These scaling factors are defined as functions of the damping ratio and, in some cases, the response period, but are independent of the nature of the expected ground shaking. Using both predictive equations for spectral ordinates at several damping levels and stochastic simulations, it is shown that the scaling factors for different damping levels vary with magnitude and distance, reflecting a dependence of the scaling on the duration of shaking that increases with the damping ratio. The options for incorporating the influence of this factor into design code specifications of displacement response spectra are discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Near-fault ground motions, and the response of elastic and inelastic single-degree-of-freedom (SDOF) systems

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2004
G. P. Mavroeidis
Abstract In order to investigate the response of structures to near-fault seismic excitations, the ground motion input should be properly characterized and parameterized in terms of simple, yet accurate and reliable, mathematical models whose input parameters have a clear physical interpretation and scale, to the extent possible, with earthquake magnitude. Such a mathematical model for the representation of the coherent (long-period) ground motion components has been proposed by the authors in a previous study and is being exploited in this article for the investigation of the elastic and inelastic response of the single-degree-of-freedom (SDOF) system to near-fault seismic excitations. A parametric analysis of the dynamic response of the SDOF system as a function of the input parameters of the mathematical model is performed to gain insight regarding the near-fault ground motion characteristics that significantly affect the elastic and inelastic structural performance. A parameter of the mathematical representation of near-fault motions, referred to as ,pulse duration' (TP), emerges as a key parameter of the problem under investigation. Specifically, TP is employed to normalize the elastic and inelastic response spectra of actual near-fault strong ground motion records. Such normalization makes feasible the specification of design spectra and reduction factors appropriate for near-fault ground motions. The ,pulse duration' (TP) is related to an important parameter of the rupture process referred to as ,rise time' (,) which is controlled by the dimension of the sub-events that compose the mainshock. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Comparison of displacement coefficient method and capacity spectrum method with experimental results of RC columns

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2004
Yu-Yuan Lin
Abstract For the performance-based seismic design of buildings, both the displacement coefficient method used by FEMA-273 and the capacity spectrum method adopted by ATC-40 are non-linear static procedures. The pushover curves of structures need to be established during processing of these two methods. They are applied to evaluation and rehabilitation of existing structures. This paper is concerned with experimental studies on the accuracy of both methods. Through carrying out the pseudo-dynamic tests, cyclic loading tests and pushover tests on three reinforced concrete (RC) columns, the maximum inelastic deformation demands (target displacements) determined by the coefficient method of FEMA-273 and the capacity spectrum method of ATC-40 are compared. In addition, a modified capacity spectrum method which is based on the use of inelastic design response spectra is also included in this study. It is shown from the test specimens that the coefficient method overestimates the peak test displacements with an average error of +28% while the capacity spectrum method underestimates them with an average error of -20%. If the Kowalsky hysteretic damping model is used in the capacity spectrum method instead of the original damping model, the average errors become -11% by ignoring the effect of stiffness degrading and -1.2% by slightly including the effect of stiffness degrading. Furthermore, if the Newmark,Hall inelastic design spectrum is implemented in the capacity spectrum method instead of the elastic design spectrum, the average error decreases to -6.6% which undervalues, but is close to, the experimental results. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A unified formulation of the piecewise exact method for inelastic seismic demand analysis including the P -delta effect

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2003
M. N. Ayd
Abstract The non-linear analysis of single-degree-of-freedom (SDOF) systems provides the essential background information for both strength-based design and displacement-based evaluation/design methodologies through the development of the inelastic response spectra. The recursive solution procedure called the piecewise exact method, which is efficiently used for the response analysis of linear SDOF systems, is re-formulated in this paper in a unified format to analyse the non-linear SDOF systems with multi-linear hysteresis models. The unified formulation is also capable of handling the P-delta effect, which generally involves the negative post-yield stiffness of the hysteresis loops. The attractiveness of the method lies in the fact that it provides the exact solution when the loading time history is composed of piecewise linear segments, a condition that is perfectly satisfied for the earthquake excitation. Based on simple recursive relationships given for positive, negative and zero effective stiffnesses, the unified form of the piecewise exact method proves to be an extremely powerful and probably the best tool for the SDOF inelastic time-history and response spectrum analysis including the P-delta effect. A number of examples are presented to demonstrate the implementation of the method. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Large displacement behaviour of a structural model with foundation uplift under impulsive and earthquake excitations

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2003
Giuseppe Oliveto
Abstract This paper considers the dynamical behaviour of a structural model with foundation uplift. The equations of motion of the system considered are derived for large displacements thus allowing for the eventual overturning of the system. The transition conditions between successive phases of motion, derived in terms of the specific Lagrangian co-ordinates used in the formulation of the equations of motion, present innovative aspects which resolve some previously inexplicable behaviour in the structural response reported in the literature. The dynamical behaviour of the model is considered under impulsive and long-duration ground motions. The minimum horizontal acceleration impulses for the uplift and the overturning of the system are evaluated in analytical form. The sensitivity of the model to uplifting and to overturning under impulsive excitations is established as a function of few significant structural parameters. Numerical applications have been performed changing either the structural parameters or the loading parameter, in order to analyse several dynamical behaviours and also to validate the analytical results. For earthquake ground motions the results, reported in the form of response spectra, show that linearized models generally underestimate, sometimes significantly, the structural response. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Study on effects of damping in laminated rubber bearings on seismic responses for a , scale isolated test structure

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2002
Bong Yoo
Abstract The effects of damping in various laminated rubber bearings (LRB) on the seismic response of a ,-scale isolated test structure are investigated by shaking table tests and seismic response analyses. A series of shaking table tests of the structure were performed for a fixed base design and for a base isolation design. Two different types of LRB were used: natural rubber bearings (NRB) and lead rubber bearings (LLRB). Three different designs for the LLRB were tested; each design had a different diameter of lead plug, and thus, different damping values. Artificial time histories of peak ground acceleration 0.4g were used in both the tests and the analyses. In both shaking table tests and analyses, as expected, the acceleration responses of the seismically isolated test structure were considerably reduced. However, the shear displacement at the isolators was increased. To reduce the shear displacement in the isolators, the diameter of the lead plug in the LLRB had to be enlarged to increase isolator damping by more than 24%. This caused the isolator stiffness to increase, and resulted in amplifying the floor acceleration response spectra of the isolated test structure in the higher frequency ranges with a monotonic reduction of isolator shear displacement. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Comparing response of SDF systems to near-fault and far-fault earthquake motions in the context of spectral regions

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2001
Anil K. Chopra
Abstract In spite of important differences in structural response to near-fault and far-fault ground motions, this paper aims at extending well-known concepts and results, based on elastic and inelastic response spectra for far-fault motions, to near-fault motions. Compared are certain aspects of the response of elastic and inelastic SDF systems to the two types of motions in the context of the acceleration-, velocity-, and displacement-sensitive regions of the response spectrum, leading to the following conclusions. (1) The velocity-sensitive region for near-fault motions is much narrower, and the acceleration-sensitive and displacement-sensitive regions are much wider, compared to far-fault motions; the narrower velocity-sensitive region is shifted to longer periods. (2) Although, for the same ductility factor, near-fault ground motions impose a larger strength demand than far-fault motions,both demands expressed as a fraction of their respective elastic demands,the strength reduction factors Ry for the two types of motions are similar over corresponding spectral regions. (3) Similarly, the ratio um/u0 of deformations of inelastic and elastic systems are similar for the two types of motions over corresponding spectral regions. (4) Design equati ns for Ry (and for um/u0) should explicitly recognize spectral regions so that the same equations apply to various classes of ground motions as long as the appropriate values of Ta, Tb and Tc are used. (5) The Veletsos,Newmark design equations with Ta=0.04 s, Tb=0.35 s, and Tc=0.79 s are equally valid for the fault-normal component of near-fault ground motions. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Stochastic models for simulation of strong ground motion in Iceland

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2001
Símon Ólafsson
Abstract Two types of modelling approaches for simulating ground motion in Iceland are studied and compared. The first type of models, named discrete-time series models (ARMA), are based solely on measured acceleration in earthquakes occurring in Iceland. The second type of models are based on a theoretical seismic source model called the extended Brune model. Based on measured acceleration in Iceland during the period 1986,1996, the parameters for the extended Brune models have been estimated. The seismic source models are presented here as ARMA models, which simplifies the simulation process. A single-layer soil amplification model is used in conjunction with the extended Brune model to estimate local site amplification. Emphasis is put on the ground motion models representing the variability in the measured earthquakes, with respect to energy, duration and frequency content. Demonstration is made using these models for constructing linear and non-linear probabilistic response spectra using a discretised version of the Bouc,Wen model for the hysteresis of the second-order system. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Duration of strong ground motion during Mexican earthquakes in terms of magnitude, distance to the rupture area and dominant site period

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2001
Eduardo Reinoso
Abstract A study of the duration of strong ground motion using accelerometric data of subduction and normal-faulting Mexican earthquakes is presented. Duration is obtained based on the time between 2.5 and 97.5 per cent of the Arias intensity. An expression to predict this duration in terms of the magnitude, distance to the rupture area and site period is proposed and compared with predictions available in the literature. The effect of large duration for very distant sites and the contribution of soft soils to the duration of strong ground motion are widely discussed. We have found that large magnitude not only yields long duration at the source, but also proportionally longer duration with distance and with dominant site period compared to small magnitude. The duration obtained from the regression is used as a parameter to obtain input and hysteretic energy and on the use of damage models available in the literature. Finally, duration is used together with the random vibration theory to predict response spectra. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Bauten in deutschen Erdbebengebieten , zur Einführung der DIN 4149: 2005

BAUTECHNIK, Issue 8 2005
Jochen Schwarz Dr.-Ing.
Die Einführung der DIN 4149: 2005 bildet eine wichtige Voraussetzung, um im Kontext der Harmonisierung europäischer Baubestimmungen ein erdbebensicheres und wirtschaftliches Bauen in den Erdbebengebieten Deutschlands zu ermöglichen. Verschiedene Phasen der Erarbeitung werden in einer chronologischen Form beleuchtet und mit einem Ausblick auf die weitere Normenentwicklung abgeschlossen. Es werden interdisziplinäre Forschungsarbeiten gewürdigt, die wesentlich dazu beigetragen haben, das Regelwerk der seismischen Lastannahmen für Bauwerke neu zu konzipieren. Insbesondere durch die Festlegung geologie- und untergrundbezogener Bemessungsspektren wird eine differenzierte Beschreibung seismischer Einwirkungen und auf die regionalen Besonderheiten deutscher Erdbebengebiete ausgerichtete Bauwerksbemessung gewährleistet. Der erreichte Grad der Harmonisierung europäischer Erdbebenbaunormen wird anhand aktueller Zonenkarten sowie der Festlegungen zu Bemessungsbeschleunigungen entlang der nationalen Grenzen beispielhaft nachvollzogen. Da die neue Gefährdungszonenkarte eine veränderte regionale Verteilung der Erdbebenzonen bedingt, wird auf die Notwendigkeit einer Bewertung der Erdbebentauglichkeit der vorherrschenden Bauweisen und die Identifikation der im Katastrophenfall bedeutenden Anlagen und Einrichtungen hingewiesen. Buildings in German seismic regions , to the introduction of the revised German Seismic Code DIN 4149: 2005. The introduction of the revised Seismic Code DIN 4149: 2005 can be regarded as an important step towards earthquake resistant and economic building design in German earthquake regions. Different stages of its elaboration are described chronologically, concluding in an outlook on the ongoing development in European code standardization. Interdisciplinary research projects, which influenced the redrafting of the general rules and the implementation of new approaches, substantially, are recognized for their contributions. In particular, the concept of geology- and subsoil-dependent response spectra enables a refined description of seismic action and building design while reflecting the existing site conditions realistically. The attained state of harmonisation of national regulations is discussed exemplary by comparing peak ground and derived design accelerations alongside the borders with neighbouring countries like Belgium, France and Switzerland. With respect to the new zoning map and the modifications of affected areas, the need of practical implementation is directed towards two tasks: evaluation of the existing building stock and the predominant building types and identification of those structures and facilities which are of high importance in cases of catastrophic events. [source]

Performance of Buildings under Earthquakes in Barcelona, Spain

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2006
Alex H. Barbat
The seismic hazard in the area of the city is described by means of the reduced 5% damped elastic response spectrum. Obtaining fragility curves for the most important building types of an urban center requires an important amount of information about the structures and the use of nonlinear structural analysis tools. The information on the buildings of Barcelona was obtained by collecting, arranging, improving, and completing the database of the housing and current buildings. The buildings existing in Barcelona are mainly of two types: unreinforced masonry structures and reinforced concrete buildings with waffled slab floors. In addition, the Arc-View software was used to create a GIS tool for managing the collected information to develop seismic risk scenarios. This study shows that the vulnerability of the buildings is significant and therefore, in spite of the medium to low seismic hazard in the area of the city, the expected seismic risk is considerable. [source]

Inelastic response spectrum: Early history

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2008
Rafael Riddell
Abstract Detailing the time period from, roughly, 1950 through 1980, this Historical Note documents the development of the initial concept of the inelastic response spectrum and how it evolved to become the basis for rational procedures for earthquake-resistant design, which are used even today. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Estimation of strength reduction factors via normalized pseudo-acceleration response spectrum

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2007
Debasis Karmakar
Abstract Estimation of design forces in ductility-based earthquake-resistant design continues to be carried out with the application of response modification factors on elastic design spectra, and it remains interesting to explore how best to estimate strength reduction factors (SRFs) for a design situation. This paper considers the relatively less explored alternative of modelling SRF spectrum via a given response spectrum. A new model is proposed to estimate the SRF spectrum in terms of a pseudo-spectral acceleration (PSA) spectrum and ductility demand ratio with the help of two coefficients. The proposed model is illustrated for an elasto-plastic oscillator, in case of 10 recorded accelerograms and three ductility ratios. The proposed model is convenient and is able to predict SRF spectrum reasonably well, particularly at periods up to 1.0 s. Coefficients of the proposed model may also be determined in case of a given design spectrum when there is uncertainty in SRF spectrum due to uncertainty in temporal characteristics of the ground motion. This is illustrated with the help of 474 accelerograms recorded in western U.S.A. and different scaled PSA spectra. It is shown that probabilistic estimates may be obtained in this situation for SRF spectrum by assuming the error residuals to be log normally distributed with period-dependent parameters. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Elastic response spectrum: a historical note

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2007
Anil K. Chopra
Abstract This is the first contribution in a new series of Historical Notes on seminal concepts in earthquake engineering and structural dynamics. It records the origins and early developments (up to the late 1960's) of the elastic response spectrum. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Spectral shape, epsilon and record selection

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2006
Jack W. Baker
Abstract Selection of earthquake ground motions is considered with the goal of accurately estimating the response of a structure at a specified ground motion intensity, as measured by spectral acceleration at the first-mode period of the structure, Sa(T1). Consideration is given to the magnitude, distance and epsilon (,) values of ground motions. First, it is seen that selecting records based on their , values is more effective than selecting records based on magnitude and distance. Second, a method is discussed for finding the conditional response spectrum of a ground motion, given a level of Sa(T1) and its associated mean (disaggregation-based) causal magnitude, distance and , value. Records can then be selected to match the mean of this target spectrum, and the same benefits are achieved as when records are selected based on ,. This mean target spectrum differs from a Uniform Hazard Spectrum, and it is argued that this new spectrum is a more appropriate target for record selection. When properly selecting records based on either spectral shape or ,, the reductions in bias and variance of resulting structural response estimates are comparable to the reductions achieved by using a vector-valued measure of earthquake intensity. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Improved design of sliding mode control for civil structures with saturation problem

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2004
Sang-Hyun Lee
Abstract A systematic and improved design procedure for sliding mode control (SMC) of seismically excited civil structures with saturation problem is provided in this paper. In order to restrict the control force to a certain level, a procedure for determining the upper limits of the control forces for single or multiple control units is proposed based on the design response spectrum of external loads. Further, an efficient procedure using the LQR method for determining sliding surfaces appropriate for different controller types is provided through the parametric evaluation of the dynamic characteristics of sliding surfaces in terms of SMC controller performance. Finally, a systematic design procedure for SMC required to achieve a given performance level is provided and its effectiveness is verified by applying it to multi-degree-of-freedom (MDOF) systems. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Seismic response analysis on the stability of running vehicles

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2002
Yoshihisa Maruyama
Abstract The seismometer network of the Japanese expressway system has been enhanced since the 1995 Kobe earthquake. Using earthquake information from the instruments, the expressways are closed if the peak ground acceleration (PGA) is larger than or equal to 80cm/s2. The aim of this regulation is to avoid secondary disasters, e.g. cars running into the collapsed sections. However, recent studies on earthquake damage have revealed that expressway structures are not seriously damaged under such-level of earthquake motion. Hence, we may think of relaxing the regulation of expressway closure. But before doing this, it is necessary to examine the effects of shaking to automobiles since the drivers may encounter difficulties in controlling their vehicles and traffic accidents may occur. In this study, a vehicle was modelled with a six-degree-of-freedom system and its responses were investigated with respect to PGA, peak ground velocity (PGV) and Japan Meteorological Agency (JMA) seismic intensity using five ground motion records. It was observed that the response of the vehicle shows a larger amplitude for the record that has larger response spectrum in the long period range compared to other records. However, similar response amplitudes of the vehicle were observed for all the records with respect to the JMA seismic intensity. The response characteristics of the vehicle model may be very useful for decision-making regarding the relaxation of the expressway closure under seismic motion. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Comparing response of SDF systems to near-fault and far-fault earthquake motions in the context of spectral regions

Long-range carbon,carbon connectivity via unsymmetrical indirect covariance processing of HSQC and HMBC NMR data

MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2006
Kirill A. Blinov
Abstract It was recently demonstrated that an IDR- (Inverted Direct Response) HSQC-TOCSY data set could be decomposed into a negatively phased direct response spectrum and a positively phased relayed response spectrum that could then be subjected to unsymmetrical indirect covariance processing for the removal of artifacts due to response overlap in the proton NMR spectrum of the molecule. Using experimentally discrete HSQC and HMBC data sets, it is shown that unsymmetrical indirect covariance processing of the pair of NMR spectra affords a presentation containing long-range carbon,carbon connectivity information. The method is demonstrated using strychnine as a model compound. The resulting data are largely free of artifacts although artifacts can arise due to proton response overlap, as previously reported. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Comparison of UV optical properties of ZnO nanoparticles dispersed in traditional organic and novel bio-molecular solvents

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010
Liqiao Qin
Abstract Two types of ZnO nanoparticles were dispersed in a bio-molecular solvent and in ethanol. The mixtures were characterized by photoluminescence and absorbance measurements. Strong UV emission was observed near the band gap of ZnO at 380 nm. The parasitic green emission which normally appears in ZnO suspensions was weakened when ZnO was dispersed in the bio-molecular solvent. Suspensions were spin-cast on quartz, and then Al contacts were deposited by a standard lift-off process via e-beam lithography. Point contact current-voltage characteristics of the samples were measured under equal intensity conditions using 340 nm UV LED and white LED sources. The ratio of the UV photo-generated current to dark current was as high as 105. Finally, the photocurrent response spectrum was measured. The results show that ZnO nanoparticle is favourable for visible blind UV photodetectors. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]