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Elastic
Kinds of Elastic Terms modified by Elastic Selected AbstractsElastic and inelastic drift performance optimization for reinforced concrete buildings under earthquake loadsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2004Chun-Man Chan Abstract This paper presents an effective optimization technique for the elastic and inelastic drift performance design of reinforced concrete buildings under response spectrum loading and pushover loading. Attempts have been made to develop an automatic optimal elastic and inelastic drift design of concrete framework structures. The entire optimization procedure can be divided into elastic design optimization and inelastic design optimization. Using the principle of virtual work, the elastic drift response generated by the response spectrum loading and the inelastic drift response produced by the non-linear pushover loading can be explicitly expressed in terms of element sizing design variables. The optimization methodology for the solution of the explicit design problem of buildings is fundamentally based on the Optimality Criteria approach. One ten-story, two-bay building frame example is presented to illustrate the effectiveness and practicality of the proposed optimal design method. While rapid convergence in a few design cycles is found in the elastic optimization process, relatively slow but steady and smooth convergence of the optimal performance-based design is found in the inelastic optimization process. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fracture behaviour of cracked carbon nanotube-based polymer composites: Experiments and finite element simulationsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2010Y. KURONUMA ABSTRACT This paper studies the fracture behaviour of cracked carbon nanotube (CNT)-based polymer composites by a combined numerical,experimental approach. Tensile tests were conducted on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K), and the critical loads for fracture instabilities were determined. Elastic,plastic finite element simulations of the tests were then performed to evaluate the,J -integrals corresponding to the experimentally determined critical loads. Scanning electron microscopy examinations were also made on the specimen fracture surfaces, and the fracture mechanisms of the CNT-based composites were discussed. [source] The evolution of the stress,strain fields near a fatigue crack tip and plasticity-induced crack closure revisitedFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2004L. G. ZHAO ABSTRACT The evolution of the stress,strain fields near a stationary crack tip under cyclic loading at selected R -ratios has been studied in a detailed elastic,plastic finite element analysis. The material behaviour was described by a full constitutive model of cyclic plasticity with both kinematic and isotropic hardening variables. Whilst the stress/strain range remains mostly constant during the cyclic loading and scales with the external load range, progressive accumulation of tensile strain occurs, particularly at high R -ratios. These results may be of significance for the characterization of crack growth, particularly near the fatigue threshold. Elastic,plastic finite element simulations of advancing fatigue cracks were carried out under plane-stress, plane-strain and generalized plane-strain conditions in a compact tension specimen. Physical contact of the crack flanks was observed in plane stress but not in the plane-strain and generalized plane-strain conditions. The lack of crack closure in plane strain was found to be independent of the material studied. Significant crack closure was observed under plane-stress conditions, where a displacement method was used to obtain the actual stress intensity variation during a loading cycle in the presence of crack closure. The results reveal no direct correlation between the attenuation in the stress intensity factor range estimated by the conventional compliance method and that determined by the displacement method. This finding seems to cast some doubts on the validity of the current practice in crack-closure measurement, and indeed on the role of plasticity-induced crack closure in the reduction of the applied stress intensity factor range. [source] Fabrication of Microcantilever Sensors Actuated by Piezoelectric Pb(Zr0.52Ti0.48)O3 Thick Films and Determination of Their Electromechanical Characteristics,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2005H. Park Abstract The integration and the device realization of Pb(Zr,,Ti)O3 (PZT) thick films on Si substrates are known to be extremely difficult because the processing temperature of the PZT thick film is close to the melting point of Si. However, PZT thick-film devices on Si warrant attention as they are appropriate for biological transducers; they generate large actuating forces and have a relatively high sensitivity for mass detection, especially in liquids. In this study, Pb(Zr0.52Ti0.48)O3 thick-film cantilever devices are successfully fabricated on a Pt/TiO2/SiNx/Si substrate using a screen-printing method and microelectromechanical systems (MEMS) process. Elastic and electromechanical properties such as the Young's modulus and transverse piezoelectric coefficient are determined from microstructural and electrical analyses for further mechanical study. The calculated Young's modulus of the thick film, 53.9,±,3.85,GPa, corresponds to the resonant frequency obtained from the measured harmonic oscillation response. The transverse piezoelectric constant, d31, of ,20.7 to ,18.8,pC,N,1 is comparable to that of a dense thin film. These values promise the possibility of determining the resonance properties of a thick-film cantilever by designing its structure and then simulating the harmonic oscillation response. Using the PZT thick-film cantilever, a strong harmonic oscillation with a quality (Q) factor of about 23 is demonstrated in water. The observation of strong harmonic oscillation in liquid implies the feasibility of precise real-time recognition of biomolecules using PZT thick-film cantilevers. [source] Intrinsic Elastic, Dielectric, and Piezoelectric Losses in Lead Zirconate Titanate Ceramics Determined by an Immittance-Fitting MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Takaaki Tsurumi The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ,50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses. [source] Elastic,ideally plastic beams and Prandtl,Ishlinskii hysteresis operatorsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2007Pavel Krej Abstract The one-dimensional equation for transversal vibrations of an elastoplastic beam is derived from a general three-dimensional system with a single-yield tensorial von Mises plasticity model. It leads after dimensional reduction to a multiyield scalar Prandtl,Ishlinskii hysteresis model whose weight function is explicitly given. The use of Prandtl,Ishlinskii operators in elastoplasticity is thus not just a questionable phenomenological approach, but in fact quite natural. The resulting partial differential equation with hysteresis is transformed into an equivalent system for which the existence and uniqueness of a strong solution is proved. The proof employs techniques from the mathematical theory of hysteresis operators. Copyright © 2007 John Wiley & Sons, Ltd. [source] Elastic and thermal properties of ,-plutoniumPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2005Hans Siethoff Abstract It has been demonstrated in recent experimental and theoretical studies, that ,-Pu exhibits highly anisotropic phonon properties. The present paper indicates, that properties related to low-energy phonons such as Debye temperature and activation energy of self-diffusion do not reflect these anisotropies, and obey the same laws as other face-centred cubic metals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ChemInform Abstract: Structural Stability and Elastic and Electronic Properties of Rhenium Borides: First Principle Investigations.CHEMINFORM, Issue 12 2009Huiyang Gou Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: First-Principles Calculations of the Elastic and Electronic Properties of the Cubic Perovskites SrMO3 (M: Ti, V, Zr and Nb) in Comparison with SrSnO3.CHEMINFORM, Issue 22 2008I. R. Shein Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Classification of Compression Bandages: Practical AspectsDERMATOLOGIC SURGERY, Issue 5 2008HUGO PARTSCH MD BACKGROUND Compression bandages appear to be simple medical devices. However, there is a lack of agreement over their classification and confusion over the use of important terms such as elastic, inelastic, and stiffness. OBJECTIVES The objectives were to propose terms to describe both simple and complex compression bandage systems and to offer classification based on in vivo measurements of subbandage pressure and stiffness. METHODS A consensus meeting of experts including members from medical professions and from companies producing compression products discussed a proposal that was sent out beforehand and agreed on by the authors after correction. RESULTS Pressure, layers, components, and elastic properties (P-LA-C-E) are the important characteristics of compression bandages. Based on simple in vivo measurements, pressure ranges and elastic properties of different bandage systems can be described. Descriptions of composite bandages should also report the number of layers of bandage material applied to the leg and the components that have been used to create the final bandage system. CONCLUSION Future descriptions of compression bandages should include the subbandage pressure range measured in the medial gaiter area, the number of layers, and a specification of the bandage components and of the elastic property (stiffness) of the final bandage. [source] Simplified inelastic seismic analysis of base-isolated structures using the N2 methodEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2010Vojko Kilar Abstract In the paper a simplified nonlinear method has been applied to the analysis of base-isolated structures. In the first part, a three-linear idealization of the capacity curve is proposed. The initial stiffness is defined based on the first yielding point in the superstructure, whereas the secondary slope depends on the failure mechanism of the superstructure. A consequence is a much more pronounced secondary slope, which does not correspond to the presumptions used in the originally proposed N2 method. A parametric nonlinear dynamic study of single degree of freedom systems with different hardening slopes and damping has been performed for an ensemble of seven EC8 spectrum-compatible artificial accelerograms. It was concluded that, in the long-period range, the equal displacement rule could be assumed also for the proposed systems with non-zero post-yield stiffness. In the second part, the proposed idealization was used for the analysis of isolated RC frame buildings that were isolated with different (lead) rubber-bearing isolation systems. The stiffness of the isolators was selected for three different protection levels and for three different ground motion intensities, which have resulted in elastic as well as moderately and fully damaged superstructure performance levels. Three different lateral load distributions were investigated. It was observed that a triangular distribution, with an additional force at the base, works best in the majority of practical cases. It was concluded that the N2 method can, in general, provide a reasonably accurate prediction of the actual top displacement, as well as of the expected damage to the superstructure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural performance assessment under near-source pulse-like ground motions using advanced ground motion intensity measuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2008Polsak Tothong Abstract This paper demonstrates the effectiveness of utilizing advanced ground motion intensity measures (IMs) to evaluate the seismic performance of a structure subject to near-source ground motions. Ordinary records are, in addition, utilized to demonstrate the robustness of the advanced IM with respect to record selection and scaling. To perform nonlinear dynamic analyses (NDAs), ground motions need to be selected; as a result, choosing records that are not representative of the site hazard can alter the seismic performance of structures. The median collapse capacity (in terms of IM), for example, can be systematically dictated by including a few aggressive or benign pulse-like records into the record set used for analyses. In this paper, the elastic-based IM such as the pseudo-spectral acceleration (Sa) or a vector of Sa and epsilon has been demonstrated to be deficient to assess the structural responses subject to pulse-like motions. Using advanced IMs can be, however, more accurate in terms of probabilistic response prediction. Scaling earthquake records using advanced IMs (e.g. inelastic spectral displacement, Sdi, and IM1I&2E; the latter is for the significant higher-mode contribution structures) subject to ordinary and/or pulse-like records is efficient, sufficient, and robust relative to record selection and scaling. As a result, detailed record selection is not necessary, and records with virtually any magnitude, distance, epsilon and pulse period can be selected for NDAs. Copyright © 2008 John Wiley & Sons, Ltd. [source] Laboratory tests of steel simple torsionally unbalanced modelsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2007Jaime De-la-Colina Abstract The objective of this work is to obtain estimations of the amplification factors , and , used for torsion design of buildings, from experiments. For this study, simple one-storey torsionally unbalanced (TU) steel models were considered. Models consisted of a deck supported on four columns with a selected arrangement of hinges at column ends. Two theoretical structural eccentricities (e = 0.05 and 0.15) were considered. Models were excited with a simple long-period pendulum consisting of a hanging platform with a forced-vibration generator on it. Eight models were tested at several excitation levels (frequencies and force magnitudes) in both ranges of behaviour: elastic and inelastic. Experiments were conducted at three frequency ratios of excitation. Registered accelerations of the pendulum platform indicate that the experimental set-up leads to excitations that resemble narrow-band seismic ground motions. Frame shear force estimations, based on accelerations recorded at both deck sides, indicate that torsion design factors (, and ,) depend on eccentricity. Estimations of frame shears based on measurements indicate that for normalized eccentricities e , 0.025, the amplification , can be between 2 and 3; while , factor resulted between 0.0 and 1.6. Copyright © 2006 John Wiley & Sons, Ltd. [source] Direct estimation of the seismic demand and capacity of oscillators with multi-linear static pushovers through IDA,EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2006Dimitrios Vamvatsikos Abstract SPO2IDA is introduced, a software tool that is capable of recreating the seismic behaviour of oscillators with complex quadrilinear backbones. It provides a direct connection between the static pushover (SPO) curve and the results of incremental dynamic analysis (IDA), a computer-intensive procedure that offers thorough demand and capacity prediction capability by using a series of nonlinear dynamic analyses under a suitably scaled suite of ground motion records. To achieve this, the seismic behaviour of numerous single-degree-of-freedom (SDOF) systems is investigated through IDA. The oscillators have a wide range of periods and feature pinching hysteresis with backbones ranging from simple bilinear to complex quadrilinear with an elastic, a hardening and a negative-stiffness segment plus a final residual plateau that terminates with a drop to zero strength. An efficient method is introduced to treat the backbone shape by summarizing the analysis results into the 16, 50 and 84% fractile IDA curves, reducing them to a few shape parameters and finding simpler backbones that reproduce the IDA curves of complex ones. Thus, vast economies are realized while important intuition is gained on the role of the backbone shape to the seismic performance. The final product is SPO2IDA, an accurate, spreadsheet-level tool for performance-based earthquake engineering that can rapidly estimate demands and limit-state capacities, strength reduction R -factors and inelastic displacement ratios for any SDOF system with such a quadrilinear SPO curve. Copyright © 2006 John Wiley & Sons, Ltd. [source] Estimate of input energy for elasto-plastic SDOF systems during earthquakes based on discrete wavelet coefficientsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2005Jun Iyama Abstract The response of an elasto-plastic single degree of freedom (SDOF) system to ground motion is estimated based on wavelet coefficients calculated by discrete wavelet transform. Wavelet coefficients represent both the time and frequency characteristics of input ground motion, and thus can be considered to be directly related to the dynamic response of a non-linear system. This relationship between the energy input into an elastic SDOF system and wavelet coefficients is derived based on the assumption that wavelets deliver energy to the structure instantaneously and the quantity of energy is constant regardless of yielding. These assumptions are shown to be valid when the natural period of the system is in the predominant period range of the wavelet, the most common scenario for real structures, through dynamic response analysis of a single wavelet. The wavelet-based estimation of elastic and plastic energy transferred by earthquake ground motion is thus shown to be in good agreement with the dynamic response analysis when the natural period is in the predominant range of the input. Copyright © 2005 John Wiley & Sons, Ltd. [source] Near-fault ground motions, and the response of elastic and inelastic single-degree-of-freedom (SDOF) systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2004G. 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] Elastic and inelastic drift performance optimization for reinforced concrete buildings under earthquake loadsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2004Chun-Man Chan Abstract This paper presents an effective optimization technique for the elastic and inelastic drift performance design of reinforced concrete buildings under response spectrum loading and pushover loading. Attempts have been made to develop an automatic optimal elastic and inelastic drift design of concrete framework structures. The entire optimization procedure can be divided into elastic design optimization and inelastic design optimization. Using the principle of virtual work, the elastic drift response generated by the response spectrum loading and the inelastic drift response produced by the non-linear pushover loading can be explicitly expressed in terms of element sizing design variables. The optimization methodology for the solution of the explicit design problem of buildings is fundamentally based on the Optimality Criteria approach. One ten-story, two-bay building frame example is presented to illustrate the effectiveness and practicality of the proposed optimal design method. While rapid convergence in a few design cycles is found in the elastic optimization process, relatively slow but steady and smooth convergence of the optimal performance-based design is found in the inelastic optimization process. Copyright © 2004 John Wiley & Sons, Ltd. [source] Behavior of moment-resisting frame structures subjected to near-fault ground motionsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2004Babak Alavi Abstract Near-fault ground motions impose large demands on structures compared to ,ordinary' ground motions. Recordings suggest that near-fault ground motions with ,forward' directivity are characterized by a large pulse, which is mostly orientated perpendicular to the fault. This study is intended to provide quantitative knowledge on important response characteristics of elastic and inelastic frame structures subjected to near-fault ground motions. Generic frame models are used to represent MDOF structures. Near-fault ground motions are represented by equivalent pulses, which have a comparable effect on structural response, but whose characteristics are defined by a small number of parameters. The results demonstrate that structures with a period longer than the pulse period respond very differently from structures with a shorter period. For the former, early yielding occurs in higher stories but the high ductility demands migrate to the bottom stories as the ground motion becomes more severe. For the latter, the maximum demand always occurs in the bottom stories. Preliminary regression equations are proposed that relate the parameters of the equivalent pulse to magnitude and distance. The equivalent pulse concept is used to estimate the base shear strength required to limit story ductility demands to specific target values. Copyright © 2004 John Wiley & Sons, Ltd. [source] Strengthening of moment-resisting frame structures against near-fault ground motion effectsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2004Babak Alavi Abstract Near-fault ground motions with forward directivity are characterized by a large pulse. This pulse-like motion may cause a highly non-uniform distribution of story ductility demands for code-compliant frame structures, with maximum demands that may considerably exceed the level of code expectations. Strengthening techniques for multi-story frame structures are explored with the objective of reducing maximum drift demands. One option is to modify the code-based SRSS distribution of story shear strength over the height by strengthening of the lower stories of the frame. The modified distribution reduces the maximum story ductility demand, particularly for weak and flexible structures. However, this strengthening technique is less effective for stiff structures, and is almost ineffective in cases in which the maximum demand occurs in the upper stories, i.e. strong and flexible structures. As an alternative, the benefits of strengthening frames with elastic and inelastic walls are evaluated. The effects of adding walls that are either fixed or hinged at the base are investigated. It is demonstrated that strengthening with hinged walls is very effective in reducing drift demands for structures with a wide range of periods and at various performance levels. Wall inelastic behavior only slightly reduces the benefits of strengthening with hinged walls.Copyright © 2004 John Wiley & Sons, Ltd. [source] Earthquake behavior of structures with copper energy dissipatorsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2004Juan C. De la Llera Abstract The earthquake behavior of structures with supplemental copper dampers is evaluated in this study. The investigation is divided into two parts: (i) an experimental work with seven pairs of hourglass copper dampers of different aspect ratios and side profiles; and (ii) a parametric study of 6-, 12-, and 25-story planar structures with elastic as well as inelastic behavior in the primary structure and copper dampers. The copper used in this study is electrolytic tough pitch (ETP) copper C11000; probably the most commonly used of all coppers; ductile, with a low-yield, and highly resistant to corrosion. Experimental results demonstrate that all copper plates reached stable angular distortions of the order of ,=25%, which implies transverse distortions in the devices larger than 40mm. The behavior of the devices is highly dependent on the aspect ratio of the plate, h/t, and a recommendation is made to use plates in the range 11 h/t,18. Plates beyond this range exhibit either large stress and strain concentrations in the neck of the device or a strong influence of axial deformations in their cyclic behavior. The inelastic earthquake response of structures with such devices shows that drift reduction factors of the order of 30 to 40% can be achieved with reasonably economic designs. It is also shown that the efficiency of these devices depends on the soil conditions and flexibility of the primary structure. Finally, it is concluded that supplemental copper dampers are a good alternative for drift reduction in a wide range of structural layouts, ranging from coupled shear-wall systems to moment-resisting frames, and for impulsive as well as non-impulsive ground motions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Predictive instantaneous optimal control of elastic structures during earthquakesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2003Kevin K. F. Wong Abstract A predictive instantaneous optimal control (PIOC) algorithm is proposed for controlling the seismic responses of elastic structures. This algorithm compensates for the time delay that happens in practical control applications by predicting the structural response over a period that equals the time delay, and by substituting the predicted response in the instantaneous optimal control (IOC) algorithm. The unique feature of this proposed PIOC algorithm is that it is simple and at the same time compensates for the time delay very effectively. Numerical examples of single degree of freedom structures are presented to compare the performance of PIOC and IOC systems for various time delay magnitudes. Results show that a time delay always causes degradation of control efficiency, but PIOC can greatly reduce this degradation compared to IOC. The effects of the structure's natural periods and the choice of control gains on the degradation induced by the time delay are also analyzed. Results show that shorter natural periods and larger control gains are both more sensitive and more serious to the degradation of control efficiency. Finally, a practical application of PIOC is performed on a six-story moment-resisting steel frame. It is demonstrated that PIOC contributes significantly to maintain stability in multiple degree of freedom structures, and at the same time PIOC has a satisfactory control performance. Copyright © 2003 John Wiley & Sons, Ltd. [source] Design of bilinear hysteretic isolation systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2003M. Fragiacomo Abstract This paper concerns the design of passive base isolation systems characterized by a bilinear hysteretic behaviour. The study refers to the case where the structure to be isolated (superstructure) vibrates according to the first mode. In this case the whole isolated structure can be modelled by a two-degree-of-freedom system. The base isolation effectiveness has been evaluated for different characteristics of the device, namely mass, strength, elastic and plastic stiffness, by using mainly energetic quantities. The optimum values for the base device have been obtained by minimizing the input energy and the displacement of the superstructure. Conclusions are drawn for superstructures with a fundamental period of 0.5s, a damping ratio of 5% and for three different kinds of earthquake ground motions. The study showed that the seismic input greatly affects the behaviour of the isolated structure, and therefore the design ground motion must be carefully chosen, dependent on the characteristics of the site. A simple procedure that involves mainly linear dynamic analyses is proposed for the design of base devices used in conjunction with superstructures of any fundamental vibration period. The procedure produces good results in spite of its simplicity, and therefore it is suitable for practical use by design engineers. Copyright © 2003 John Wiley & Sons, Ltd. [source] Soil,pile,structure interaction under SH wave excitationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2003K. K. Koo Abstract A continuum model for the interaction analysis of a fully coupled soil,pile,structure system under seismic excitation is presented in this paper. Only horizontal shaking induced by harmonic SH waves is considered so that the soil,pile,structure system is under anti-plane deformation. The soil mass, pile and superstructure were all considered as elastic with hysteretic damping, while geometrically both pile and structures were simplified as a beam model. Buildings of various heights in Hong Kong designed to resist wind load were analysed using the present model. It was discovered that the acceleration of the piled-structures at ground level can, in general, be larger than that of a free-field shaking of the soil site, depending on the excitation frequency. For typical piled-structures in Hong Kong, the amplification factor of shaking at the ground level does not show simple trends with the number of storeys of the superstructure, the thickness and the stiffness of soil, and the stiffness of the superstructure if number of storeys is fixed. The effect of pile stiffness on the amplification factor of shaking is, however, insignificant. Thus, simply increasing the pile size or the superstructure stiffness does not necessarily improve the seismic resistance of the soil,pile,structure system; on the contrary, it may lead to excessive amplification of shaking for the whole system. Copyright © 2003 John Wiley & Sons, Ltd. [source] Inelastic deformation response of SDOF systems subjected to earthquakesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2002Rafael Riddell Abstract Performance-based seismic design requires reliable methods to predict earthquake demands on structures, and particularly inelastic deformations, to ensure that specific damage-based criteria are met. Several methods based on the response of equivalent linear single-degree-of-freedom (SDOF) systems have been proposed to estimate the response of multi-degree-of-freedom structures. These methods do not offer advantages over the traditional Veletsos,Newmark,Hall (VNH) procedure, indeed, they have been shown to be inaccurate. In this study, the VNH method is revised, considering the inelastic response of elastoplastic, bilinear, and stiffness-degrading systems with 5% damping subjected to two sets of earthquake ground motions. One is an ensemble of 51 earthquake records in the Circumpacific Belt, and the other is a group of 44 records in California. A statistical analysis of the response data provides factors for constructing VNH inelastic spectra. Such factors show that the ,equal-displacement' and ,equal-energy' rules to relate elastic and inelastic responses are unconservative for high ductilities in the acceleration- and velocity-sensitive regions of the spectrum. It is also shown that, on average, the effect of the type of force,deformation relationship of non-linear systems is not significant, and responses can be conservatively predicted using the simple elastoplastic model. Copyright © 2001 John Wiley & Sons, Ltd. [source] Comparing response of SDF systems to near-fault and far-fault earthquake motions in the context of spectral regionsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2001Anil 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] Muscle, tendon, and somatotropin responses to the restriction of muscle blood flow induced by KAATSU-walk trainingEQUINE VETERINARY JOURNAL, Issue S36 2006T. ABE Summary Objective: The efficacy of KAATSU training has been demonstrated in human athletes, both as a therapeutic method as well as a training aid. The purpose of this study was to investigate the effects of slow walk training combined with restriction of muscle blood flow (KAATSU) on muscle and tendon size. Methods: Six healthy, unfit Standardbred mares performed walking (240 m/min for 10 min and then 5 min recovery) with KAATSU, and 6 mares performed walking without KAATSU. A specially designed elastic cuff1 was placed at the most proximal position of the forelegs and inflated to a pressure of 200,230 mmHg throughout the walking and recovery sessions. The training was conducted once a day, 6 days/week for 2 weeks. Skeletal muscle thickness and tendon thickness were measured using B-mode ultrasound at baseline and after 2 weeks of training. Venous blood samples were obtained before the first acute exercise and 5, 15 and 60 min afterwards. Serum somatotropin concentration was determined using a commercially available equine-specific ELISA kit. Results: The acute increase in plasma somatotropin was 40% greater (P<0.05) in the KAATSU-walk group than in the Control-walk group 5 min after exercise and remained elevated (P<0.05) at 15 and 60 min post exercise compared with the Control-walk group. After 2 weeks of training, muscle thickness increased (P<0.05) 3.5% in the KAATSU-walk group but did not change in the Control-walk group (0.7%). Tendon thickness did not change (P>0.05) in either group. Conclusions: These data demonstrate that KAATSU training can induce muscle hypertrophy in horses and suggest that KAATSU training may provide significant therapeutic/rehabilitative value in horses, as has been shown in man. [source] Developments in Failure and Damage Modeling for UD, 2D, and 3D Composite Materials,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Lucio Raimondo This paper outlines three examples of original solutions for the modeling of three classes of composite materials, which have increasing fiber architectural complexity. Results are presented from application of a novel approach for dynamic elastic and failure modeling of UD composites, and novel failure and damage modeling approaches for 2D and 3D composites, respectively. A comparison between numerical and experimental results shows that the newly proposed strategies have excellent predictive capabilities. [source] Bi-Stable Adhesion of a Surface with a DimpleADVANCED ENGINEERING MATERIALS, Issue 5 2010Robert M. McMeeking In this paper, we propose a new adhesive system of dimpled surfaces. The principle is derived from a contact mechanics model. The material is assumed to be linear elastic and isotropic, and attraction between the surfaces of the half-spaces is modeled via the concept of a specific adhesion energy. It is found that large and small detachments are unstable and will either grow or shrink spontaneously when their sizes are perturbed. It is shown that this phenomenon can lead to a new bi-stable adhesive system in which weak adhesion can be converted to strong adhesion by the application of pressure. [source] Martensite Formation in a Ductile Cu47.5Zr47.5Al5 Bulk Metallic Glass Composite,ADVANCED ENGINEERING MATERIALS, Issue 6 2007S. Pauly A Cu47.5Zr47.5Al5 alloy was solidified into rods of 2, 3 and 5 mm diameter and the microstructures as well as the elastic and plastic properties were investigated along the length of each rod. It was found that neither the microstructure nor the mechanical properties vary significantly along the length of the specimens, except for the 5 mm diameter rod where the top part was proved to be fully crystalline containing cubic B2 CuZr (austenite) and monoclinic CuZr (martensite) phases. The differently solidified alloys show high strength and a distinct deformability under uniaxial compression and a work hardening-like behavior. [source] Czochralski-grown Single Crystals with Acentric Symmetry Group 32,ADVANCED ENGINEERING MATERIALS, Issue 7 2004R.B. Heimann Single crystals with calcium gallium germanate (Ca3Ga2Ge4O14, CGG) structure such as langasite La3Ga5SiO14 (LGS), its niobium (,langanite', La3Ga5.5Nb0.5O14, LGN) and tantalum (,langataite', La3Ga5.5Ta0.5O14, LGT) analogs as well as strontium niobium gallium silicate (Sr3NbGa3Si2O14, SNGS) and strontium tantalum gallium silicate (Sr3TaGa3Si2O14, STGS) were grown with high perfection by the Czochralski pulling technique. Specific electric conductivity, optical activity, and dielectric, piezoelectric, bulk and surface acoustic, elastic, and electro-optic properties were measured. [source] | |||||||||||||||||||||||||||||||