bluuebunny/crossref_metadata_2025_split huggingface dataset:
SusChem – eine Erfolgsstory
Authors: Hoer Renate 
Published: April 2007

AbstractSusChem – was ist das eigentlich? Viele Chemikerinnen und Chemiker wissen es nicht (vermuten dahinter aber richtigerweise die Sustainable Chemistry), die Öffentlichkeit ist darüber erst recht nicht informiert. Es ist an der Zeit, dass SusChem bekannter wird.
Chemie der Vergänglichkeit
Authors: Fischer‐Henningsen Doris 
Published: April 2007

AbstractSie mögen anspruchsvolle Krimis, und brauchen aber etwas Abstand von Henning Mankells Komissar Wallander oder Åke Edwardsons Kommissar Winter? Dann ist dieser Kriminalroman vielleicht etwas für Sie, der nicht nur eine spannende Handlung hat, sondern auch noch die Möglichkeiten und Grenzen der Forensik insbesondere auf dem Gebiet der Entomologie aufzeigt.
Dynamic vertical compliance of strip foundations in layered soils
Authors: Israil A. S. M. , Ahmad S. 
Published: April 2007

AbstractIn this paper, results of a detailed investigation on the dynamic response of rigid strip foundations in viscoelastic soils under vertical excitation are presented. An advanced boundary element algorithm developed by incorporating isoparametric quadratic elements and a sophisticated self‐adapting numerical integration scheme has been used for this investigation. Foundations supported on three types of soil profiles, namely, homogeneous half‐space, stratum‐over‐half‐space and stratum‐over‐bedrock are considered. The influence of material properties like Poisson's ratio and material damping as well as the influence of geometrical properties such as depth of embedment and layer thickness are studied. The effect of the type of contact at the soil‐foundation interface is also investigated.
Optimization of the stochastic response of a bridge isolation system with hysteretic dampers
Authors: Xiaoming Li 
Published: April 2007

AbstractA bridge structure with a seismic isolation system consisting of rubber bearings and hysteretic dissipators is considered. The non‐linear equations of motion are derived for the first mode vibration and the stochastic response to a white noise or a filtered white noise ground acceleration is determined by using the method of equivalent linearization. The sensitivity of the stochastic response to principal pàrameters for the bridge is investigated. Results of optimum design of the isolation system are presented.
Scattering of plane harmonic SH, SV, P and rayleigh waves by non‐axisymmetric three‐dimensional canyons: A wave function expansion approach
Authors: Eshraghi Hossein , Dravinski Marijan 
Published: April 2007

AbstractScattering of elastic waves by three‐dimensional canyons embedded within an elastic half‐space is investigated by using a wave function expansion technique. The geometry of the canyon is assumed to be non‐axisymmetric. The canyon is subjected to incident plane Rayleigh waves and oblique incident SH, SV and P waves. The unknown scattered wavefield is expressed in terms of spherical wave functions which satisfy the equations of motion and radiation conditions at infinity, but they do not satisfy stress‐free boundary conditions at the half‐space surface. The boundary conditions are imposed locally in the least‐squares sense at several points on the surface of the canyon and the half‐space.Through a comparative study the validity and limitations of two‐dimensional approximations (antiplane strain and plane strain models) have been examined. It is shown that scattering of waves by three‐dimensional canyons may cause substantial change in the surface displacement patterns in comparison to the two‐dimensional models. These results emphasize the need for three‐dimensional modelling of realistic problems of interest in strong ground motion seismology and earthquake engineering.
Coupling of boundary and finite elements for soil‐structure interaction problems
Authors: von Estorff Otto , Kausel Eduardo 
Published: April 2007

AbstractThe investigation of complex soil‐structure interaction problems is usually carried out with numerical solution procedures such as the finite element or the boundary element method. It must be noted, however, that the choice of one or the other of these approaches is not just a matter of preferences; depending on the type of the problem under consideration, either boundary or finite elements may be more advantageous. A considerable expansion in the computational power can be obtained, on the other hand, if one resorts to hybrid schemes which retain the main advantages of the two methods and eliminate their respective disadvantages.This paper presents results obtained with a boundary element‐finite element coupling procedure, and discusses its applicability to some representative soil‐structure interaction problems. The structures considered are elastic systems, such as foundations, tunnels and filled trenches (modelled by finite elements), which are coupled with homogeneous elastic halfspaces (modelled by boundary elements). The examples demonstrate the importance of using a model that includes wave radiation effects.The coupling approach is formulated entirely in the time domain so that an extension of the algorithm to non‐linear analyses seems to present no further difficulties.
Dynamic parameter identification for non‐linear isolation systems in response spectrum analysis
Authors: Tsai Hsiang‐Chuan , Kelly James M. 
Published: April 2007

AbstractThe response spectrum method has been widely used in earthquake engineering design, but cannot be directly applied to non‐linear systems such as the lead‐filled rubber bearing used in base isolation systems. An appraoch to determine the equivalent linearized stiffness and damping coefficient of the lead‐filled rubber bearing by use of the results of shaking table tests is developed. Comparisons of time histories for the equivalent linear systems and the actual model show the method gives accurate maxima for displacement and acceleration and at the appropriate times. It is found that the identified parameters vary with the maximum deformation and the simplified formulae that can optimally describe the variations are derived. Using these formulae, an iterative algorithm using the response spectrum method to calculate the dynamic response of buildings isolated by lead‐filled rubber bearings is also presented.
Seismic demand in medium‐ and long‐period structures
Authors: Fajfar Peter , Vidic Tomaž , Fischinger Matej 
Published: April 2007

AbstractBased on the results of an extensive parametric study of elastic and inelastic response of SDOF systems, in which the most important structural parameters were varied and ground motions of very different characteristics were taken into account, simple formulae for determining the seismic demand in SDOF systems with natural periods in the medium‐ and long‐period range are proposed. Seismic demand is expressed in terms of the mean values of maximum relative displacements and maximum input energy. These results can be used to provide rough estimates of structural behaviour when different damage models are applied. As well as this, the proposed formulae can be used to construct design spectra of the Newmark‐Hall type.
Centrifugal modelling of dynamic soil‐structure interaction
Authors: Weissman Karen , Prevost Jean H. 
Published: April 2007

AbstractThis paper presents a centrifuge model that is capable of realistically representing soil‐structure systems subjected to earthquake‐like excitation. The model is validated by performing (i) free field soil tests, (ii) dynamic soil‐structure interaction tests and (iii) a numerical analysis of the experimental results. The free field experiments show that the simulated earthquake, which is generated by the hammer‐exciter plate method, is similar in amplitude and frequency content to a real earthquake. The experiments also demonstrate that a confined soil sample can satisfactorily model a horizontal soil stratum of infinite lateral extent when the containment walls are lined with an absorptive material to attenuate wave reflections that would otherwise occur. Measurements of the acceleration at different locations on the free soil surface indicate that the surface motion is fairly uniform over a relatively large area. This is further confirmed by a comparison made between the measured free and scattered field motions for a surface foundation. Next, a series of soil‐structure interaction tests are performed which examine the dependence of radiation damping on the natural frequencies of the structure relative to the fundamental frequency of the soil stratum. The experimental results are shown to be consistent with established theories. Finally, the experimental results are used to compute the stiffness and damping parameters of a two degree of freedom numerical model of the soil‐structure system. The experimental parameters are shown to be in good agreement with calssical text book formulae. This study demonstrates that the centrifuge model consistently behaves as expected for simple, but realistic, dynamic soil and soil‐structure systems, and can, therefore, be used with confidence to examine more complicated systems that are not yet fully understood.
Evaluation of seismic energy in structures
Authors: Uang Chia‐Ming , Bertero Vitelmo V. 
Published: April 2007

AbstractResearch engineers use two types of energy equations to study single‐degree‐of‐freedom (SDOF) systems subject to earthquake induced ground motions. The first method uses an absolute energy formulation; the second method uses a relative energy formulation. While the relative energy formulation has been used in the majority of previous investigations, this study shows that the absolute energy equation is physically more meaningful. For a given ductility ratio, the input energy demands calculated by both methods are significantly different for both the short and long period ranges although the results are similar in the intermediate period range. A comparison between the analytically predicted absolute input energy of a SDOF system with the experimentally measured input energy of a six‐storey braced steel frame shows good correlation.
Seismic response of simple structures using spring‐assisted sliding slabs with coulomb damping
Authors: Singh M. P. , Malushte S. R. 
Published: April 2007

AbstractCoulomb damping can be utilized effectively to reduce the dynamic response of structures subjected to seismic ground motions. To activate this damping, some parts of a vibrating structure are allowed to slide at rough interfaces. The dynamic response of structures provided with sliding interfaces at the base, between a floor slab and frame and in the cross bracings of a frame has been examined recently. In this paper, a simple slab sliding system provided with a spring to introduce a recovery mechanism and to reduce the sliding displacement requirement for low frequency structures has been examined. The equations of motion for this system are developed. An approach is presented to solve these coupled equations for earthquake induced ground motions. Structures with varying frequency and friction characterisics are considered and the numerical results are presented in response spectrum form. It is observed that, in low frequency structures, provision of a rather weak spring can reduce the sliding displacement requirements without significantly increasing the forces in the supporting frame and the acceleration input to supported secondary systems.
Transverse response of offshore pipelines to random ground motion
Authors: Datta T. K. , Mashaly E. A. 
Published: April 2007

AbstractA method is presented for the determination of the transverse response of the idealized suspended span of an offshore pipeline to random seismic input. The method is based on spatial discretization of the pipe with nodal lumped masses. The earthquake is assumed to be a stationary random process characterized by a power spectral density function. The cross spectral density function between two random seismic excitations along the pipe length is defined with the help of a local earthquake power special density function, which is assumed to be the same for the two end supports of the pipeline, and a frequency dependent weighted function which decays exponentially with distance from the pipe supports. The solution is obtained in the frequency domain using the spectral approach and is presented in terms of r.m.s. displacements and stresses. The formulation adequately includes the pressure drag effect which tends to dampen the pipe motions. Utilizing this method of analysis, several idealized pipe sea bed configurations, in which the pipe is anchored between two end blocks and subjected to horizontal ground excitations normal to the pipe axis, have been analysed to predict the influence of certain important parameters on the response.
Application of fractional derivatives to seismic analysis of base‐isolated models
Authors: Koh Chan Ghee , Kelly James M. 
Published: April 2007

AbstractThe concept of fractional derivatives is employed in the formulation of a stress‐strain relationship for elastomers. An oscillator consisting of a mass and a ‘fractional’ Kelvin element is used to model elastomeric bearings used in base isolation systems. Efficient numerical multi‐step schemes are developed for the dynamic analysis of a single‐degree‐of‐freedom ‘fractional oscillator’ in the time domain. Numerical examples show that these multi‐step schemes are in good agreement with the Laplace and Fourier solutions. When applied to shaking table tests of a base‐isolated bridge deck, the fractional derivative model is found to agree well with the experimental results.
Analytical predictions of the seismic response of friction damped timber shear walls
Authors: Filiatrault A. 
Published: April 2007

AbstractA new concept for the earthquake resistant design of timber shear wall structures is proposed. By providing friction devices in the corners of the framing system of the shear wall, its earthquake resistance and damage control potential can be enhanced considerably. During severe earthquake excitations, the friction devices slip and a large portion of the seismic energy input is dissipated by friction rather than by inelastic deformation of the sheathing‐to‐framing connectors. A simple numerical model is developed and results of inelastic time‐history dynamic analyses show the superior performance of the friction damped timber shear walls compared to conventional shear wall systems. The proposed friction devices act both as safety valves by limiting the inertia forces transmitted to the structure, and as structural dampers by dissipating a significant portion of the seismic energy input. The devices can be used in any configuration of the framing system to accommodate architectural or construction requirements. The damping system may also be conveniently incorporated in existing timber shear wall buildings to upgrade significantly their earthquake resistance.
Non‐stationary structural response with evolutionary spectra using seismological input model
Authors: Quek Ser‐Tong , Teo Yen‐Peng , Balendra Thambirajah 
Published: April 2007

AbstractA recently developed seismological model of ground motion is incorporated into the non‐stationary random vibration theory making use of Priestley's evolutionary power spectral density. A general method of computing the input power spectrum is proposed and shown to reduce to the classical method when the input and the output are taken as stationary. Based on the concepts of Yang's non‐stationary envelopes and first‐passage reliability estimates via extreme point process, a statistical response spectrum for the pseudo‐velocity is developed. Comparisons made among the results of non‐stationary analysis with different modulating functions, and that of the stationary approximation, on SDOF linear structures with 5 per cent damping show that the type ofmodulating function chosen has little effect on the magnitudes of mean pseudo‐velocities, provided the input power spectrum is properly scaled, and that the stationary approximation produces conservative results for structures with natural periods greater than 0.5 sec.
Optimum design of actively controlled structures
Authors: Pantelides C. P. 
Published: April 2007

AbstractThe optimum design of seismic structures equipped with active controls is presented. The design variables are structural parameters, such as structural stiffness or moment of inertia. The optimization procedure is carried out in two stages. First, the optimal control forces are expressed in closed form, as implicit functions of the design variables. In the second stage, the structural parameters are varied in order to minimize a structural weight objective function. The algorithm is applied to structural systems under earthquake excitations, for displacement, frequency and control force constraints.
Response of piles and pile groups to travelling SH‐waves
Authors: Mamoon S. M. , Banerjee P. K. 
Published: April 2007

AbstractThe response of single piles and pile groups under vertically and obliquely incident seismic waves is obtained using the hybrid boundary element (BEM) formulation. The piles are represented by compressible beam‐column elements and the soil as a hysteretic viscoelastic half‐space. A recently developed Green function corresponding to the dynamic Mindlin problem is implemented in the numerical formulation. Exact analytical solutions for the differential equations for the piles under distributed harmonic excitations are used. Treating the half‐space as a three‐dimensional elastic continuum, the interaction problem is formulated by satisfying equilibrium and displacement compatibility along the pile‐soil interface. Solutions adopted for the seismic waves are obtained by direct integration of the differential equations in terms of amplitudes. Salient features of the seismic response are identified in several non‐dimensional plots. Results of the analyses compare favourably with the limited data available in the literature.
Amplification of elastic waves by a three dimensional valley. Part 2: Transient response
Authors: Mossessian Tomi K. , Dravinski Marijan 
Published: April 2007

AbstractTransient response of three dimensional dipping layers of different shapes subjected to incident P, SV, SH and Rayleigh waves is investigated. The time domain response is constructed from steady state solutions through the Fourier synthesis. An indirect boundary integral equation method is applied to calculate the required steady state solutions. The material of the half‐space and the layer is assumed to be linear, weakly inelastic, homogeneous and isotropic.Numerical results show that the maximum amplification of motion is strongly dependent upon the type of incident wave, the shape of the basin and signal frequency. The change in the shape of the valley from hemispherical to semi‐prolate causes a significant increase in the amplitude of surface waves near the edges; however, the maximum amplification of motion near the centre of the valley decreases. This phenomenon is especially apparent for the case of an incident P wave. In comparison to the corresponding two dimensional responses, the amplitude of motion near the centre of the valley is in general higher for three dimensional models.
Effective time‐domain soil‐structure interaction analysis based on FFT algorithm with causality condition
Authors: Hayashi Yasuhiro , Katukura Hiroshi 
Published: April 2007

AbstractWe propose an effective and reliable time‐domain substructure technique which takes soil‐structure interaction effects into account and uses the flexibility coefficients of unbounded soil obtained in the frequency domain. Compared with previous methods, the frequency points to calculate flexibility coefficients, and computational loads in the calculation of time‐domain interaction forces, are reduced.In the formulation, we have assumed the flexibility coefficient to be a periodic function, obtained within the bandlimited frequency range, which also includes the predominant frequencies of the structure and incident wave. Then we simulate the periodic flexibility coefficients using discrete impulse responses in the time‐domain analyses. However, the real and imaginary parts of the bandlimited flexibility coefficients do not form a Hilbert transform pair; the discrete impulse responses should be modified to be causal for the time‐domain analyses. We present various discrete impulse responses which have been obtained from only the real part, only the imaginary part and from both the real and imaginary parts of the frequency‐domain flexibility coefficients by FFT with causality conditions. Through a numerical example the relationship between the modified discrete impulse responses and the validity of the time‐domain substructure method is presented.
Response of multi‐degree‐of‐freedom structures with sliding supports
Authors: Yang Yeong‐Bin , Lee Tzu‐Ying , Tsai I.‐Chau 
Published: April 2007

AbstractThe response of multi‐degree‐of‐freedom (MDOF) structures with sliding supports is studied. The problem of sliding structures is a discontinuous one in that different numbers of equations of motion with varying forcing functions are required for the sliding and non‐sliding phases. The numerical difficulties involved in this regard in an incremental finite element analysis can be circumvented through the introduction of a fictitious spring for the sliding support. Such a treatment enables one to study the higher mode effects on MDOF sliding structures under the excitation of harmonic or earthquake motions. The dynamic characteristics of MDOF sliding structures will be highlighted in the analysis of a four‐storey shear building with sliding support.
Response of multi‐span beams to spatially incoherent seismic ground motions
Authors: Zerva Aspasia 
Published: April 2007

AbstractThe response of continuous two‐ and three‐span beams of various lengths subjected to spatially varying seismic ground motions is evaluated. Stochastic representations of the seismic ground motions are used as input at the supports of the structures, and sensitivity analyses of the response with respect to the degree of correlation between the support motions are performed. The validity of the commonly used assumption of equal support motion is examined. Square‐roots of mean‐square values of total displacements, bending moments and shear forces are outputs of the analyses. The results indicate that fully correlated motions may produce higher or lower response than partially correlated motions, depending on the dynamic characteristics of the structure, the response quantity (bending moment or shear force) that is evaluated, the position along the axis of the beam where the response quantity is evaluated, the separation between the natural frequencies of the structure and the dominant frequencies of the input motions, and on the degree of partial correlation between the support motions.
Diagonal brace with ductile knee anchor for aseismic steel frame
Authors: Balendra Thambirajah , Sam Ming‐Tuck , Liaw Chih‐Young 
Published: April 2007

AbstractA new structural system for earthquake resistant steel structures is investigated in this paper. This new framing system, called the knee‐brace‐frame (KBF), is a braced frame with diagonal braces connected to ductile knee members. The diagonal braces provide the lateral stiffness, whereas the knee anchors yield in flexure to dissipate energy during severe seismic excitation. To assess the inelastic characteristics of the KBF, a large scale model of a KBF was tested using the pseudodynamic test procedure. The experimental results are compared with analytical results obtained from a DRAIN‐2D model. It is found that, with an appropriate design of knee anchors, the KBF can be made to be ductile to dissipate energy during severe seismic excitation.