bluuebunny/crossref_metadata_2025 huggingface dataset:
Stille Reaction: An Important Tool in the Synthesis of Complex Natural Products
Authors: De Souza Marcus Vinicius Nora
Published: April 2007

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, please click on HTML or PDF.
Total Synthesis of Borrelidin
Authors: Nagamitsu Tohru , Harigaya Yoshihiro , Omura Satoshi
Published: April 2007

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, please click on HTML or PDF.
Polyfluorinated Binaphthol Ligands in Asymmetric Catalysis
Authors: Chen Yu , Yudin Andrei K.
Published: April 2007

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, please click on HTML or PDF.
Allylic Fluorides
Authors: Roig R. , Percy J. M.
Published: April 2007

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, please click on HTML or PDF.
Benzylic Fluorides
Authors: Murthy A. Sai Krishna , Tardivel R. , Gree R.
Published: April 2007

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, please click on HTML or PDF.
Propargylic Fluorides
Authors: Miles J. A. L. , Percy J. M.
Published: April 2007

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, please click on HTML or PDF.
Pd(O‐Ac)2/Silica in Ionic Liquid: A Green Heck Catalyst
Authors: Polshettiwar Vivek
Published: April 2007

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, please click on HTML or PDF.
Fruit Fly as a Tractable Model Animal for Infectious Diseases: Implication for Understanding of Host‐pathogen Interaction
Authors: Shinzawa Naoaki , Kanuka Hirotaka
Published: April 2007

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, please click on HTML or PDF.
Bacterial Strategies for Escaping the Bactericidal Mechanisms by Macrophage
Authors: Yamamoto Tomoko
Published: April 2007

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, please click on HTML or PDF.
Reversible Binding of Heme to Proteins in Cellular Signal Transduction
Authors: Hou Shangwei , Reynolds Mark F. , Horrigan Frank T. , Heinemann Stefan H. , Hoshi Toshinori
Published: April 2007

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, please click on HTML or PDF.
Does an Apple a Day Keep the Doctor Away Because a Phytoestrogen a Day Keeps the Virus at Bay? A Review of the Antiviral Properties of Phytoestrogens
Authors: Martin J. H. J. , Crotty S. , Warren P. , Nelson P. N.
Published: April 2007

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, please click on HTML or PDF.
Science + Fiction: Isaac Asimov zum 15. Todestag
Authors: Schneider Thomas
Published: April 2007

“Eine Science‐Fiction‐Erzählung ist eine Erzählung, [...] die ohne naturwissenschaftlichen Inhalt überhaupt nicht stattfände.” Diese Definition des Science‐Fiction‐Autors Theodore Sturgeon trifft auf das fiktionale Werk Isaac Asimovs in ganz besonderer Weise zu. Seine Science Fiction war stark geprägt von fundierten naturwissenschaftlichen Kenntnissen und außergewöhnlich kreativer Gestaltungskraft. Beides macht sie zu zeitlosen Klassikern. Auch wenn Asimovs naturwissenschaftlichen Sachbüchern heute eine geringere Bedeutung zukommt, sind sie immer noch ausdrückliche Beweise dafür, dass wissenschaftliche Sachverhalte in einer klaren und sogar unterhaltsamen Weise zu Papier gebracht werden können.
Energielösungen für die Zukunft? Weiße Biotechnologie
Authors: Sell Dieter , Puls Jürgen , Ulber Roland
Published: April 2007

Angesichts hoher Ölpreise und der sich abzeichnenden globalen Klimaveränderungen erscheinen biotechnisch hergestellte Energieträger als vielversprechende Zukunftsoption. Mit seinen Jahresproduktionsmengen von 2 Mio t Biodiesel, 560.000 t Bioethanol und seinen 2.700 Biogasanlagen befindet sich Deutschland in Sachen Bioenergie in der vorderen Hälfte der Industrienationen. Vorgestellt werden die Möglichkeiten, die die weiße Biotechnologie zur Herstellung von Energieträgern bietet.
Berlin‐Dahlem und Schöneberg
Authors: Schwedt Georg
Published: April 2007

In Berlin‐Dahlem befinden sich ehemalige Kaiser‐Wilhelm‐Institute (heute der Max‐Planck‐Gesellschaft bzw. Institute der FU Berlin) zwischen Thielallee und Faradaystraße, Gräber bedeutender Chemiker auf dem Friedhof Dahlemer Dorfkirche und auf dem alten St.‐Matthäus‐Kirchhof in Schöneberg. Ein weiterer Lokaltermin findet in Dahlem in der Garystraße im Garten des heutigen Archivs zur Geschichte der Max‐Planck‐Gesellschaft statt.
Arsenicin A: Die erste natürliche Polyarsenverbindung
Authors: Kummeter Manuela
Published: April 2007

Vor der Küste Australiens liegt das zu Frankreich gehörige Archipel Neukaledonien. In dessen Gewässern konnte eine europäische Forschergruppe jüngst die Existenz einer natürlichen organischen Polyarsenverbindung, des Arsenicin A, nachweisen. Die Strukturaufklärung gelang durch intensive NMR‐ und massenspektroskopische Untersuchungen; ausschlaggebend war am Ende jedoch die Synthese einer Modellverbindung.
Substituiertes Cyclobutan mit antidiabetischer Wirkung
Authors: Hille‐Rehfeld Annette
Published: April 2007

An der Regulation des Blutglucosespiegels sind neben dem Insulin auch Gastrointestinalhormone wie das Glucagon‐ähnliche Peptid 1 beteiligt. Synthetische Agonisten dieses Peptidhormons sind die neuesten Hoffnungsträger für die medikamentöse Diabetestherapie.
Homolävo‐Chiralität durch Autokatalyse
Authors: Jaenicke Lothar
Published: April 2007

Aminosäuren in der Zelle sind praktisch immer L‐Aminosäuren. Dabei muss man annehmen, dass in der mysteriösen Ursuppe L‐ und D‐Formen mit gleicher Wahrscheinlichkeit vorhanden waren.
Schnelle und übersichtliche Auswertung von Emissionsprüfungen mittels ADAM
Authors: Kirchner Doris , Hartstock Stefan
Published: April 2007

Im Rahmen der Ad‐hoc‐Gruppe “Bodenbeläge und Klebstoffe”, die von Juli 2002 bis Dezember 2003 tagte und den produktspezifischen Teil der “Zulassungsgrundsätze zur gesundheitlichen Bewertung von Bauprodukten in Innenräumen” erarbeitet hat, wurde angeregt, den Prüfstellen ein einheitliches EDV‐basiertes Auswerteprogramm zur Verfügung zu stellen. Zur letzten Sitzung der Ad‐hoc‐Gruppe lag bereits eine erste arbeitsfähige Version vor. Verbesserungen von Funktionen, Vereinfachungen von Eingaben, Hinterlegung einer zweiten NIK‐Liste etc. wurden im weiteren Verlauf seitens des DIBt erarbeitet und technisch umgesetzt. Mittlerweile steht das Auswerteprogramm mit dem Namen “ADAM” (AgBB/DIBt‐Auswertemaske) auf der DIBt‐Homepage als kostenpflichtiger Download zur Verfügung. Nachfolgend soll das Programm kurz beschrieben werden.
Das DIBt als Partner im Twinning Projekt “Umsetzung der Eurocodes in Lettland”
Authors: Lutz Holger
Published: April 2007

Unter dem Begriff “Twinning” (engl.: to be twinned = in Partnerschaft verbunden sein) werden Partnerschaftsprojekte im Rahmen der Europäischen Union verstanden, die auf wichtigen Politikfeldern den Auf‐ und Ausbau institutioneller Strukturen in den Kandidaten‐ und neuen Mitgliedstaaten fördern sollen. Alle Beitrittswilligen haben die enorm schwierige Aufgabe, den “Acquis Communautaire”, den die “alten” Mitgliedstaaten in Jahrzehnten erworben haben, in allerkürzester Zeit auf ihrem Staatsgebiet ebenfalls zu installieren.
Non‐linear earthquake response of concrete gravity dams part 2: Behaviour
Authors: El‐Aidi Bahaa , Hall John F.
Published: April 2007

The earthquake response of the idealized Pine Flat Dam—water—foundation system of Part 1 is investigated with emphasis on the non‐linear behaviour associated with concrete cracking and water cavitation. It is shown that water cavitation has little effect on the dam response. On the other hand, concrete cracking plays a significant role, as demonstrated by several analyses on dams with initial cracks or weak lift joints and by a final analysis on a homogeneous dam. The analyses encountered a number of numerical difficulties requiring further mesh refinement, and these are described. A possible failure mode associated with inclined cracks is revealed.
Earthquake analysis with generalized plasticity model for saturated soils
Authors: Desai C. S. , Galagoda H. M.
Published: April 2007

A plasticity based constitutive model for anisotropic behaviour of soils is implemented in a finite element procedure based on the generalized Biot theory for the dynamic non‐linear response of porous materials. The model represents a version in the hierarchical approach of constitutive modelling and allows for inelastic response during loading, unloading and reloading. The procedure has been verified previously with respect to closed‐form solutions for wave propagation in porous media. In this paper, it is used to predict the behaviour of a realistic structure‐saturated porous soil system subjected to earthquake loading. Both linear and non‐linear analyses have been performed. It has been found that the predicted responses from the two analyses are significantly different; for example, in comparison with the linear analysis the non‐linear response shows increased magnitudes and zones of concentration of pore water pressures, increased magnitudes of horizontal displacements, decreased magnitudes of vertical displacements and increased magnitudes of shear stresses.
Seismic response of offshore structures in random seas
Authors: Yamada Y. , Iemura H. , Kawano K. , Venkataramana K.
Published: April 2007

A study of the dynamic response of offshore structures to simultaneous loadings by random earthquake ground motions and random sea waves is presented. Emphasis is placed on the evaluation of dynamic soil‐structure interaction effects and also on the evaluation of non‐linear hydrodynamic damping effects due to sea waves for the seismic response. The structure is discretized using the finite element method. Sea waves are represented by Bretschneider's power spectrum and the Morison equation defines the wave forcing function. The Tajimi‐Kanai power spectrum is used for the horizontal ground acceleration due to earthquakes. The governing equations of motion are obtained by the substructure method. Response analysis is carried out using the frequency‐domain random vibration approach.

It is found that the first few vibrational modes contribute significantly to the dynamic response. The response due to earthquake loadings is larger when the soil‐structure interaction effects are considered. The hydrodynamic damping forces are higher in random seas than in still water and sea waves reduce the seismic response of offshore structures. Studies on the first passage probabilities of response indicate that small sea waves enhance the reliability of offshore structures against earthquake forces.
Lanczos method for dynamic analysis of damped structural systems
Authors: Nour‐Omid B. , Regelbrugge M. E.
Published: April 2007

In this paper we extend the Lanczos algorithm for the dynamic analysis of structures7 to systems with general matrix coefficients. The equations of dynamic equilibrium are first transformed to a system of first order differential equations. Then the unsymmetric Lanczos method is used to generate two sets of vectors. These vectors are used in a method of weighted residuals to reduce the equations of motion to a small unsymmetric tridiagonal system.

The algorithm is further simplified for systems of equations with symmetric matrices. By appropriate choice of the starting vectors we obtain an implementation of the Lanczos method that is remarkably close to that in Reference 7, but generalized to the case with indefinite matrix coefficients. This simplification eliminates one of the sets of vectors generated by the unsymmetric Lanczos method and results in a symmetric tridiagonal, but indefinite, system. We identify the difficulties that may arise when this implementation is applied to problems with symmetric indefinite matrices such as vibration of structures with velocity feedback control forces which lead to symmetric damping matrices.

This approach is used to evaluate the vibration response of a damped beam problem and a space mast structure with symmetric damping matrix arising from velocity feedback control forces. In both problems, accurate solutions were obtained with as few as 20 Lanczos vectors.
Response of base‐isolated buildings to wind loading
Authors: Henderson Paul , Novak Milos
Published: April 2007

The response of base‐isolated buildings to gusting wind is analysed theoretically based on experimental data obtained in a boundary layer wind tunnel. A comparison is made with the response evaluated using existing codes. A special procedure, similar to that of current codes, for computing the alongwind and torsional responses of base‐isolated buildings is presented.
Optimum strong‐motion array geometry for source inversion—II
Authors: Iida Masahiro
Published: April 2007

Optimum strong‐motion array geometry for source inversions is again determined for each of three types of earthquake faults: strike‐slip, dip‐slip and offshore subduction thrust. The method is the same as employed in a previous study;1 however, use of a complete Green's function in an elastic half‐space provides better results for engineering practice. It is found that the complete Green's function is capable of stabilizing the accuracy of an inversion solution obtained using theoretical seismograms, regardless of the differences in array configuration. The optimum strong‐motion array for a strike‐slip fault is characterized by stations well distributed in azimuth, while the optimum array for a dip‐slip event has stations arranged in a grid‐shaped form. The array geometries obtained here are grossly similar to those in the previous study,1 which were derived using only the far‐field S waves, and are more consistent with those proposed at the 1978 International Workshop on Strong‐Motion Earthquake Instrument Arrays.2.
Feasibility and robustness of predictive control of building structures by active cables
Authors: López‐Almansa F. , Rodellar J.
Published: April 2007

In this paper a theoretical and numerical analysis on the robustness and the practical feasibility of a control system of an experimental model of a building structure is performed. This model has a mechanical actuator employing active cables and the control algorithm is based on a predictive strategy. In order to test the robustness one simulates numerically different control experiments under two kinds of non‐ideal conditions: (i) discrepancies between the parameters of the system (mass, natural frequencies and the time delay in the actuator) and those assumed in the formulation of the control algorithm; (ii) operation of the active cables out of the operation range caused by excitations stronger than expected. In order to assess the feasibility, in every control experiment one obtains the values of four performance indices which provide full information about the features of the control action. The numerical results show that predictive control by active cables is robust and feasible.
Dynamic response of multiply connected primary‐secondary systems
Authors: Muscolino Giuseppe
Published: April 2007

A method to evaluate the dynamic response of composite multiply connected primary‐secondary systems is presented. For this purpose the nodal equations of motion of the composite system are given in ‘total’ and ‘relative’ coordinates. In the framework of the component‐mode synthesis method a coordinate transformation, here defined as an admissible one, is used to reduce the nodal equations of motion. This coordinate transformation is theoretically and numerically compared with the coordinate transformation usually used in the literature, which generally gives larger errors with respect to the former when a reduced number of nodes is considered.
Experimental behaviour of reinforced concrete walls under earthquake loading
Authors: Elnashai A. S. , Pilakoutas K. , Ambraseys N. N.
Published: April 2007

The experimental work and first results of a recently completed experimental research programme investigating the response of reinforced concrete (RC) walls under earthquake (EQ) loading are discussed in this paper. A brief literature review is given as a prelude to the outline of research objectives. The tests are presented in two groups according to the scale of models. For the 1:5 scale tests, a modified similitude relation for small scale reinforced concrete dynamic modelling is developed. Based on the chosen model parameters, the design of the isolated RC walls is given. The test‐rig set‐up and the EQ input signals suitable for testing the model on the Imperial College shake‐table are also discussed. Preliminary observations regarding stiffness, strength and failure modes of the RC wall models are given. Experimental results from the shake‐table are compared to tests, at the same scale, under static cyclic conditions. For the scale 1:2–5 cyclic tests a different test‐rig assembly is designed. The test results are given in three pairs of flexurally similar walls followed with general observations and discussion. Finally, conclusions are drawn regarding experimental procedures and behaviour patterns of the tested models.
Non‐linear steady state vibration and dynamic snap through of shallow arch beams
Authors: Leung A. Y. T. , Fung T. C.
Published: April 2007

The non‐linear steady state vibration of shallow arch beams is studied by a finite element method based on the principle of virtual work. Both the free and forced periodic vibrations are considered. The axial and flexural deformations are coupled by the induced axial force along the beam element. The spatial discretization is achieved by the usual finite element method and the steady state nodal displacements are expanded into a Fourier series. The harmonic balance method gives a set of non‐linear algebraic equations in terms of the vibrating frequency and the Fourier coefficients of nodal displacements. The non‐linear algebraic equations are solved by the Newtonian algorithm iteratively. The combined algorithm is called the incremental harmonic balance method. The importance of the conditions of completeness and balanceability is presented. Since the non‐linearity is essentially softening, different orders of internal resonances between two modes can occur repeatedly. Isolated response curves are possible and are connected to the bifurcation of a particular excited mode.
Local‐soil and source‐mechanism effects in the 1986 kalamata (Greece) earthquake
Authors: Gazetas George , Dakoulas Panos , Papageorgiou Apostolos
Published: April 2007

An Ms ∼ 6 earthquake, originating at a normal fault directly underneath the town of Kalamata, caused substantial structural damage to reinforced‐concrete and masonry buildings, to contemporary as well as centuries‐old churches, and to a major harbour quaywall. Two accelerograms were recorded on stiff alluvial deposits. The seismologic and engineering facts of the earthquake are presented in the first half of the paper. Particular attention is paid to the non‐uniform pattern of damage distribution, at both regional and local scale. The second half of the paper investigates the possible role of the ‘local soil conditions’ and of the ‘mechanics of the source’ in the observed pattern of damage and in the amplitude and frequency composition of the two records. To this end, numerical modelling of site‐specific motions is attempted using state‐of‐practice methods, and utilizing the results of an extensive geotechnical exploration programme. It is concluded that substantial evidence does exist indicating that both soil and source effects have contributed to the non‐uniform spatial distribution of damage. The effect of through‐soil ‘filtering’ of the seismic waves appears most evident in the coastal neighbourhoods of the town, where the underlying loose saturated silty sands in the over‐50 m‐deep soil deposit may have played a beneficial role in weakening the ground‐surface shaking; the structural damage in these areas was insignificant. Qualitative arguments are also put forward for explaining some aspects of the observed pattern of damage in terms of fault orientation and ‘directivity’ effects.
Assessment of errors in the newmark method in structural dynamics
Authors: Warburton G. B.
Published: April 2007

In the Newmark and other approximate step‐by‐step methods, having introduced assumptions in order to transform the differential equations, which are characteristic of response problems, into simultanéous equations, successive solutions lead to a response‐time history. In this paper numerical results and formulae are given for the errors which are generated by this procedure. These errors are oscillatory in nature and, in general, the oscillations increase in magnitude as the number of time steps increases. Recommendations for upper limits on the time step, which will provide acceptable accuracy for a wide range of system and excitation parameters, are presented.
Soil‐structure interaction effects for laterally excited liquid storage tanks
Authors: Veletsos A. S. , Tang Y.
Published: April 2007

A comprehensive study is made of the effects of soil‐structure interaction on the response of liquid containing, upright, circular cylindrical tanks subjected to a horizontal component of ground shaking. A simple, physically motivated method of analysis is employed which elucidates the effects and relative importance of the principal actions involved. Both the impulsive and convective actions of the liquid are examined. The interrelationship of the tank responses to horizontal and rocking actions of the foundation is established, and the well known mechanical model for laterally excited, rigid tanks supported on a non‐deformable medium is generalized to permit consideration of the effects of tank and ground flexibilities and base rocking. Critical responses are evaluated for harmonic and seismic excitations over wide ranges of tank proportions and soil stiffnesses, and the results are presented in a form convenient for use in practical applications. In addition to a precise method of analysis, an approximate, hand‐computation method is presented with which the effects of the primary parameters may be evaluated readily. The soil‐structure interaction effects in the latter approach are provided for by modifying the natural frequency and damping of the tank‐liquid system and evaluating its response to the prescribed free‐field ground motion considering the tank to be rigidly supported at the base. The requisite modifications may be determined from information presented herein. It is shown that soil‐structure interaction may reduce significantly the impulsive components of response but that it has a negligible effect on the convective components.
Ground motion amplification by cylindrical valleys embedded in a layered medium
Authors: Bouden M. , Khair K. R. , Datta S. K.
Published: April 2007

The phenomenon of localized amplification of seismic waves due to subsurface irregularities has attracted the attention of seismologists and engineers for many years. In this paper we present a hybrid numerical method to investigate the ground motion amplification due to sedimentary basins. This method combines the integral representation and the finite element to solve the scattering problem due to an arbitrary cylindrical scatterer. A study is done on two shapes of valleys to show the effect of the angle of incidence, the incident wave type and the layering on the amplification of the surface displacement components by different valleys.
Dynamic behaviour of rocking two‐block assemblies
Authors: Psycharis Ioannis N.
Published: April 2007

The dynamic behaviour of systems consisting of two blocks, one placed on the top of the other, and free to rock without sliding, is examined in this analysis. The equations of motion for each ‘mode’ of vibration are derived and criteria for the initiation of rocking and the transition between modes are given. During vibration, the system continuously changes from one mode to another and this makes the response non‐linear. This transition may be accompanied by impact, in which case dissipation of energy occurs, the amount of which depends on the relative velocities and the dimensions of the blocks. Also, redistribution of the kinetic energy of the system in the blocks happens. In most cases, the fractional contribution from the upper block to the system energy increases, which results in a larger and longer response of the top block, compared to the vibration of the lower one.
Hybrid experiments on non‐linear earthquake‐induced soil‐structure interaction
Authors: Toki Kenzo , Sato Tadanobu , Kiyono Junji , Garmroudi Nozar Kishi , Emi Susumu , Yoshikawa Masaaki
Published: April 2007

Non‐linear seismic soil‐structure interaction is studied through a hybrid procedure using the pseudo‐dynamic testing (PDT) method which is modified to take into account frequency dependence and developed for foundation‐soil systems. The numerical scheme used in conventional PDT is improved by introduction of a time‐dependent pseudo‐forcing function which is derived from frequency‐dependent dynamic characteristics of the system by means of Hilbert transformation in the frequency domain. Surface, shallow and caisson foundation models that differed in size and depth of embedment were used. The mechanical characteristics of the systems were determined from static and forced vibration dynamic tests. An amplitude scaling technique was used for three recorded accelerograms.
Three‐dimensional response of a cylindrical canyon in a layered half‐space
Authors: Luco J. E. , Wong H. L. , De Barros F. C. P.
Published: April 2007

An indirect boundary‐method formulation to obtain the three‐dimensional response of an infinitely long canyon of uniform but arbitrary cross‐section cut in a layered viscoelastic half‐space is presented. Seismic excitation in the form of plane elastic waves acting at an arbitrary angle with respect to the axis of the canyon is considered. Numerical results for SH‐, SV‐ and P‐wave excitation of a circular canyon and of a canyon with a topography similar to that in the vicinity of Pacoima Dam are discussed in some detail.
Probabilistic representation and transmission of earthquake ground motion records
Authors: Masri S. F. , Miller R. K. , Traina M.‐I.
Published: April 2007

A relatively simple and straightforward procedure is given for representing analytically defined or data‐based covariance kernels of arbitrary random processes in a compact form that allows its convenient use in later analytical random vibration response studies. The method is based on the spectral decomposition of the random process by the orthogonal Karhunen‐Loeve expansion and the subsequent use of least‐squares approaches to develop an approximating analytical fit for the data‐based eigenvectors of the underlying random process. The resulting compact analytical representation of the random process is then used to derive a closed‐form solution for the non‐stationary response of a damped SDOF harmonic oscillator. The utility of the method for representing the excitation and calculating the mean‐square response is illustrated by the use of an ensemble of acceleration records from the 1971 San Fernando earthquake.
A semi‐analytical boundary element method for scattering of waves in a half space
Authors: Yuan Cao Zhi , Xiong Zhu Jian , Cheung Y. K.
Published: April 2007

A boundary element method using finite strip discretization is proposed to investigate the three‐dimensional scattering behaviour of waves in a half space. The scatterers examined are an irregular surface and a cavity in a half space. The numerical examples demonstrate the remarkably good accuracy of the results and validate the application of the present method to solve three‐dimensional scattering problems.
Earthquake physical damage and functional serviceability of lifeline network models
Authors: Kawakami Hideji
Published: April 2007

The connectivity of lifeline systems is studied in this paper in terms of two ratios: ‘damage ratio’, which is the degree of physical damage to the system, and is defined as the expected number of failures per unit length or per link; and ‘service ratio’, which is a measurement of system operation. First, the relationship between the two ratios in a historic event is examined. Second, a method is developed for determining this relationship in simple network systems immediately following an earthquake. Density function, expected value and covariance of service ratio are calculated as functions of the damage ratio. Even in a simple checkerboard‐type network, the density function of the service ratio has two peaks. Third, the variation in reliability of the network is examined with respect to difference in scale and configuration of the network, which may accompany growth of the community. When the damage ratio is small, the service ratio of a complex network is as large as, or larger, than that of a simple network. This pattern is, however, reversed for larger damage ratios. Finally, the relationship prior to operation restoration is examined. During the initial stages of restoration, the service ratio increases steeply, almost linearly, with decrease in the damage ratio. The increase then slows in the last stages of restoration.
A methodology for dynamic analysis of linear structure‐foundation systems with local non‐linearities
Authors: Ibrahimbegovic Adnan , Wilson Edward L.
Published: April 2007

An efficient computational technique is presented for the dynamic analysis of large linear structural systems with local non‐linearities. The earthquake response evaluation for many practical structures belongs to this class of problems. The technique provides a rational approach to the earthquake‐resistant design of structure‐foundation systems with predetermined non‐linearities occurring along the structure‐foundation interface. Various possibilities for base isolation systems are naturally fitted within the proposed framework. In particular, we address uplifting of the structure as a natural base isolation concept. We use the dynamic substructuring technique and an efficient numerical algorithm which accommodates non‐proportional damping as a consistent way to reduce significantly the computational effort, which is in sharp contrast to the vast majority of ad‐hoc simplified models used for the same purpose. A numerical example which demonstrates the vibration isolation effect when the uplifting of the concrete gravity dam occurs is also presented.
Optimal weight absorber designs for vibrating structures exposed to random excitations
Authors: Lee Jimmy
Published: April 2007

Optimal 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

Whereas 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

An 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

Criteria 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

The 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

In 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

This 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

The 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

The 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.
On enhancement of accuracy in direct integration dynamic response problems
Authors: Bismarck‐Nasr Maher N. , Marmo Oliveira A. De
Published: April 2007

Enhancement of accuracy of the direct integration methods used in structural dynamic response analysis is presented. The accuracy achieved is obtained at the same time as the cost of the problem solution is reduced. The method presented is based on Richardson's extrapolation technique.
Shaking table study of concrete gravity dam monoliths
Authors: Donlon William P. , Hall John F.
Published: April 2007

A 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

The 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

A 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

The 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

A 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

The 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.