bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupled lateral‐torsional behaviour of frame structures under earthquake loading
Authors: Maheri M. R. , Chandler A. M. , Bassett R. H. 
Published: April 2007

AbstractA series of parametrically defined experimental model structures has been tested under earthquake base loading using the SERC national U.K. earthquake simulator. The models have been designed with variable ratios of torsional to lateral stiffness, and with both symmetric and asymmetric mass distributions. This paper first describes the tests carried out to determine the basic dynamic model properties and the establishment of idealized analytical models which give accurate predictions of model behaviour under steady‐state loading and free‐vibration conditions. Secondly, a detailed discussion is made of the two highly coupled structural models having uncoupled torsional to lateral frequency ratio Rf = 1.2, commenting on the ability of the modal analysis procedures to predict accurately the maximum recorded responses. It is concluded that the theory underestimates the significance of the fundamental torsional mode of vibration in the combined structural response, and overestimates the contribution of the first lateral mode. These effects compensate each other on the side of the structure which is most severely affected by torsional response, but produce large inaccuracies on the side of the building which is commonly assumed to be affected beneficially by torsional coupling.
Evaluation of factors influencing the inelastic seismic performance of torsionally asymmetric buildings
Authors: Chandler A. M. , Duan X. N. 
Published: April 2007

AbstractThis paper addresses some fundamentally contradictory conclusions drawn by Tso and Ying1 and the authors2 regarding the additional seismic ductility demand in asymmetric building structures and the adequacy of certain code torsional provisions. It also clarifies a number of issues arising from the different approaches employed in the two studies. The Mexico 76 and 87 code torsional provisions are taken as examples. Results show that the structural element at the stiff edge is the more critical and that the Mexico 76 code torsional provisions (among others) are inadequate, substantially underestimating the strength demand of this element. On the other hand, the Mexico 87 code torsional provisions are found to be over‐conservative. Recommendations are also given for improving the form and effectiveness of these code torsional provisions.
Analytical prediction of the collapse earthquake for R/C buildings: Case studies
Authors: Kappos Andreas J. 
Published: April 2007

AbstractAn analytical methodology for estimating the values of behaviour factors (q‐factors), suggested in a companion paper, is applied to two typical reinforced concrete structures, a frame and a dual system, designed according to current European trends in seismic design. The two case studies clearly indicated the need to consider both local and overall collapse criteria, since either one can be critical for the determination of the behaviour factor, depending on the type of the structure. The calculated values of q‐factors were close to, but higher than those specified by modern seismic codes, the larger discrepancy occurring in the case of the dual system.
A modal superposition pseudo‐force method for dynamic analysis of structural systems with non‐proportional damping
Authors: Claret A. M. , Venancio‐Filho F. 
Published: April 2007

AbstractA modal superposition pseudo‐force method for the dynamic analysis of structural systems with non‐proportional damping is presented. The method combines the advantages of the classical modal superposition method and the pseudo‐force method. When the system damping is non‐proportional, the dynamic equilibrium equations in generalized coordinates are coupled through the damping terms. In the present method, these coupled equations are solved by an iterative process in which the coupling terms are treated as pseudo‐forces. A proof of the convergence of the iterative process is given. Numerical examples show the good convergence characteristics of the process and the good accuracy of the obtained results.
Shear hysteretic elasto‐plastic earthquake response of soil systems
Authors: Elgamal Ahmed‐W. 
Published: April 2007

AbstractAn analytical/numerical procedure is developed to calculate the shear hysteretic elasto‐plastic earthquake response of soil systems. Dynamic level ground response as well as earth‐dam response is evaluated on the basis of the analytical one‐dimensional (ID) shear‐beam and shear‐wedge models respectively. Soil is modelled as an elasto‐plastic hysteretic material following the principles of flow or incremental plasticity. Stiffness and strength degradation of this material may be specified as a function of accumulated plastic strain and associated pore‐pressure build‐up. The entire numerical procedure may be executed on a personal computer and consequently qualifies as a versatile tool in conducting preliminary design calculations or parametric‐type investigations. Using this procedure, the responses of the Mexico City SCT site during the September 19, 1985 earthquake, and the California Wildlife site during the November 24, 1987 earthquake are computed and compared to those actually observed.
Damage costs for houses and farms as a function of intensity in the 1987 edgecumbe earthquake
Authors: Dowrick David J. 
Published: April 2007

AbstractThis paper describes an analysis of damage costs to house and farm property in the Ms = 6.6 Edgecumbe, New Zealand earthquake of 2 March 1987. The study investigated damage ratios for dwellings, their contents and domestic motor vehicles. The damage costs were converted to damage ratios by dividing them by the total value of the relevant property in the intensity zones concerned. The mean values and statistical distributions of these damage ratios were then found, the lognormal distribution fitting very well.The mean damage ratio for house buildings at MM intensity IX was 0.080 and the mean damage ratios were generally smaller than previous studies had shown. The mean damage ratios were similar for buildings and contents from MM6 to MM9, but there was no correlation between building and contents damage on an individual basis.
An improved response spectrum method for calculating seismic design response. Part 1: Classically damped structures
Authors: Singh M. P. , Maldonado G. O. 
Published: April 2007

AbstractA good response spectrum method, used for calculating the seismic design response for design inputs defined in terms of response spectra, should be able to include the effect of the higher modes, even though they may be truncated and not explicitly considered in the analysis. It should also be able to include the intercorrelation of the retained modes as well as their correlation with truncated modes. Herein one such method based on a suitable combination of the mode displacement and mode acceleration formulations of structural dynamics is proposed. Several numerical examples are presented to demonstrate the efficiency of the proposed approach vis‐a‐vis some other commonly used response spectrum approaches.
Impact interactions between two vibration systems under random excitation
Authors: Jing Hung‐Sying , Young Mindhu 
Published: April 2007

AbstractThe exact stationary solutions of the random response of two special vibration systems with impact interactions are formulated in this paper. Between the two systems, the Hertz contact law is used to model the contact process during vibration. A clearance is also introduced. The excitation is assumed to be a stationary white Gaussian process with zero mean and acting on the two systems independently. By assuming the ratio of the excitation and damping parameter of each system to be the same, the exact solutions can be found through solving the time‐independent Fokker‐Planck equation. The effects of contact stiffness, clearance and the system properties on the response are discussed probabilistically. From this study, it is found that, under some cases, the contact phenomena still play an important role on the response even when the clearance is larger than three times the root mean square response of the corresponding linear systems.
Combined dynamic response of primary and multiply connected cascaded secondary subsystems
Authors: Falsone G. , Muscolino G. , Ricciardi G. 
Published: April 2007

AbstractA method is proposed for the deterministic and stochastic non‐stationary analysis of linear composite systems with cascaded secondary subsystems subjected to a seismic input. This method makes it possible to evaluate, by means of a unitary formulation, the deterministic and non‐stationary stochastic response of both classically and non‐classically damped subsystems and of secondary subsystems multiply supported on the primary one, as well as the ground. The proposed procedure is very efficient from a computational point of view, because of the Kronecker algebra systematically employed. Indeed, by using this algebra, it is possible to obtain in a very compact and elegant form the eigenproperties of the composite system as a function of the eigenproperties of the two subsystems taken separately. Moreover, it is possible to write the first order differential equations governing the evolution of the second order moments of the response and to solve them in a simple way.
Response of multiply supported rigid plate to spatially correlated seismic excitations
Authors: Hao Hong 
Published: April 2007

AbstractThe ground motions produced by an earthquake at the multiple support points of large structures can differ considerably. In this study, the quasi‐static, the dynamic and the total structural responses of a multiply supported rigid plate to spatially varying multiple ground motion inputs are analysed. The results, together with those obtained by neglecting ground motion phase shifts and those by neglecting ground motion coherency losses, are compared with the corresponding structural responses to a single input. The comparisons show that the single input method overestimates translational responses and underestimates rotational responses. They also show that the responses are sometimes overestimated and sometimes underestimated by neglecting the coherency loss effects between the multiple ground motion excitations.
Time‐harmonic boussinesq problem for a continuously non‐homogeneous soil
Authors: Vrettos Christos 
Published: April 2007

AbstractAn analytical solution is presented for the response of a non‐homogeneous, compressible, elastic half‐space to a time‐harmonic vertical point load on its surface. The shear modulus is assumed to increase continuously with depth. The model is chosen so as to describe uniformly deposited cohesionless soils. Expressions for displacements and stresses in the interior of the half‐space medium are derived by means of Hankel transforms and contour integration. Selected numerical results are presented to demonstrate the influence of non‐homogeneity. Finally, some effects are pointed out to be used in connection with vibration tests for subsoil investigation.
Dynamic response of surface foundations on layered media
Authors: Swaddiwudhipong S. , Chow Y. K. , Tan S. C. , Phoon K. F. 
Published: April 2007

AbstractThe steady‐state dynamic responses of both flexible and rigid massless foundations with complex geometries on layered media are studied by the finite layer method. The discussion covers both the horizontal and vertical responses including the rocking mode of vibration. The effect of various parameters, namely, the size of the domain, the number of harmonic terms and the material damping of the soil media, on the convergence and accuracy of the results is investigated. Non‐homogeneous soil profiles are treated as a matter of course. The results obtained are compared with solutions by other theoretical methods.
Vibration of surface foundations of arbitrary shapes
Authors: Liou Gin‐Show 
Published: April 2007

AbstractPresented is a systematic procedure for generating impedance (or compliance) matrices for foundations with arbitrary shapes, resting on an elastic half‐space medium. A technique to decompose prescribed harmonic tractions on the half‐space medium is employed to solve analytically the differential wave equations in cylindrical coordinates. However, the interaction stresses due to the vibration of a foundation with arbitrary shape are described in rectangular coordinates, and assumed to be piecewise constant in the region of the arbitrary shape. A coordinate transformation matrix is introduced for the piecewise constant tractions in order to use the solution of the differential wave equations in cylindrical coordinates. Finite element modelling is assumed in rectangular coordinates for the foundation itself. The impedance matrix is then obtained for the finite element model, using a variational principle and the reciprocal theorem. A simple example of a rigid square plate resting on a half‐space medium and subjected to vertical excitation is used to demonstrate the efficiency and effectiveness of the procedure. Some numerical aspects are investigated and some possible extensions of the procedure are also discussed.
The influence of preform on the modes of vibrating beams
Authors: Kelly James M. , Sackman Jerome L. , Javid Ahmad 
Published: April 2007

AbstractA theoretical analysis is presented of a vibratory system in which it is possible to eliminate an unwanted mode of vibration by using that mode as an initial deformation of the system. The analysis shows that this is possible in straight beams with end restraints in axial deformation. The mathematical problem leads to an eigenvalue problem of a type not normally encountered.In the paper examples are given for the changes in eigenfrequency and mode shape produced by the initial preformed shape of the beam for cases where the preform is proportional to a mode of the straight beam and when the preform is unrelated to any mode.The analysis shows that, while elimination of a mode in the strict sense is not achieved, the results can be interpreted for practical purposes in this way.
Investigation of a Ni(Mg,Fe)O Cathode for Molten Carbonate Fuel Cell Applications
Authors: Randström S. , Lagergren C. , Scaccia S. 
Published: April 2007

AbstractThe Molten Carbonate Fuel Cell (MCFC) converts chemical energy into electrical energy and heat. Since the working temperature is high, less expensive materials can be used compared to low temperature fuel cells. However, the components of the fuel cell still need to be improved. The dissolution of the NiO cathode has, for a long time, been a problem for the Molten Carbonate Fuel Cell (MCFC) and this area is still the focus for MCFC component research. In this study, solubility measurements for a NiO cathode material doped with magnesium and iron are carried out and the electrochemical performance of this cathode material is tested under the standard conditions of the MCFC over 2,000 hours and compared with the performance of a standard NiO cathode. After operation, nickel precipitation in the matrices is investigated. It is concluded that a NiO cathode with magnesium and iron could be a viable candidate material for the MCFC.
Increased Metal Utilization in Carbon‐Supported Pt Catalysts by Adsorption of Preformed Pt Nanoparticles on Colloidal Silica
Authors: Zeng J. , Lee J. Y. , Chen J. , Shen P. K. , Song S. 
Published: April 2007

AbstractPt/C electrocatalysts, aimed at maximizing the electrochemical surface area (ECSA) and consequently the specific mass activity of fuel cell reactions, are obtained by firstly depositing Pt nanoparticles on colloidal silica (Pt‐silica), followed by the adsorption of the latter onto a carbon support. This method of catalyst preparation increases Pt metal utilization and generates accessible void space in the interpenetrating particle network of carbon and silica for the facile transport of reactants and products. Both electrochemical hydrogen adsorption/desorption and CO oxidation measurements show an increase in the ECSA using this approach. Methanol electrooxidation is used as a test reaction to evaluate the catalytic activity. It is found that the silica modified catalyst is three times as active as a catalyst prepared without silica, under otherwise identical conditions.
Intergenerational predictors of diurnal cortisol secretion in early childhood
Authors: Ben‐Dat Fisher Dahlia , Serbin Lisa A. , Stack Dale M. , Ruttle Paula L. , Ledingham Jane E. , Schwartzman Alex E. 
Published: April 2007

AbstractThe present study examined potential intergenerational links that may contribute to atypical patterns of diurnal cortisol secretion in early childhood. Salivary cortisol samples were collected across 1 waking day in 36 pre‐school children whose mothers are participants in an ongoing longitudinal project. Hierarchical Linear Modeling (HLM) identified statistically significant predictors of individual differences in daily cortisol trajectories. Children displayed relatively low post‐awakening values and flatter cortisol trajectories across the day as a function of unsupportive maternal behaviour, second‐hand smoke and maternal histories of social withdrawal in childhood. These results suggest that individual differences in young children's pattern of diurnal cortisol are associated with a variety of current and historical maternal characteristics and behaviours. The identification of intergenerational predictors of children's diurnal neuroendocrine functioning may provide new insights into the transfer of health and developmental risk from parent to child. Copyright © 2007 John Wiley & Sons, Ltd.
Central bank intervention and exchange rate volatility, its continuous and jump components
Authors: Beine Michel , Lahaye Jérôme , Laurent Sébastien , Neely Christopher J. , Palm Franz C. 
Published: April 2007

AbstractWe analyse the relationship between interventions and volatility at daily and intra‐daily frequencies for the two major exchange rate markets. Using recent econometric methods to estimate realized volatility, we employ bi‐power variation to decompose this volatility into a continuously varying and jump component. Analysis of the timing and direction of jumps and interventions imply that coordinated interventions tend to cause few, but large jumps. Most coordinated operations explain, statistically, an increase in the persistent (continuous) part of exchange rate volatility. This correlation is even stronger on days with jumps. Copyright © 2007 John Wiley & Sons, Ltd.
Speeding up parallel GROMACS on high‐latency networks
Authors: Kutzner Carsten , Van Der Spoel David , Fechner Martin , Lindahl Erik , Schmitt Udo W. , De Groot Bert L. , Grubmüller Helmut 
Published: April 2007

AbstractWe investigate the parallel scaling of the GROMACS molecular dynamics code on Ethernet Beowulf clusters and what prerequisites are necessary for decent scaling even on such clusters with only limited bandwidth and high latency. GROMACS 3.3 scales well on supercomputers like the IBM p690 (Regatta) and on Linux clusters with a special interconnect like Myrinet or Infiniband. Because of the high single‐node performance of GROMACS, however, on the widely used Ethernet switched clusters, the scaling typically breaks down when more than two computer nodes are involved, limiting the absolute speedup that can be gained to about 3 relative to a single‐CPU run. With the LAM MPI implementation, the main scaling bottleneck is here identified to be the all‐to‐all communication which is required every time step. During such an all‐to‐all communication step, a huge amount of messages floods the network, and as a result many TCP packets are lost. We show that Ethernet flow control prevents network congestion and leads to substantial scaling improvements. For 16 CPUs, e.g., a speedup of 11 has been achieved. However, for more nodes this mechanism also fails. Having optimized an all‐to‐all routine, which sends the data in an ordered fashion, we show that it is possible to completely prevent packet loss for any number of multi‐CPU nodes. Thus, the GROMACS scaling dramatically improves, even for switches that lack flow control. In addition, for the common HP ProCurve 2848 switch we find that for optimum all‐to‐all performance it is essential how the nodes are connected to the switch's ports. This is also demonstrated for the example of the Car‐Parinello MD code. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Explicit treatment of force contribution from alignment tensor using overdetermined linear equations and its application in NMR structure determination
Authors: Rathinavelan Thenmalarchelvi , Im Wonpil 
Published: April 2007

AbstractResidual dipolar coupling (RDC) provides valuable information about the orientation of each internuclear vector in a macromolecule with respect to the static magnetic field. However, structure determination utilizing RDC still remains challenging without additional restraints such as NOE. In this context, a novel approach has been developed to efficiently extract structural information from RDC by successive application of singular value decomposition (SVD) method in the course of NMR structure determination. Force contribution from the alignment tensor is rigorously formulated in the context of SVD, and assessments have been made to verify its numerical accuracy. The efficacy of this approach is illustrated by showing that RDC restraints alone can restore a distorted β‐hairpin to native‐like structure using the replica‐exchange molecular dynamics simulations. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Comparison of solvation‐effect methods for the simulation of peptide interactions with a hydrophobic surface
Authors: Sun Yu , Dominy Brian N. , Latour Robert A. 
Published: April 2007

AbstractIn this study we investigated the interaction behavior between thirteen different small peptides and a hydrophobic surface using three progressively more complex methods of representing solvation effects: a united‐atom implicit solvation method [CHARMM 19 force field (C19) with Analytical Continuum Electrostatics (ACE)], an all‐atom implicit solvation method (C22 with GBMV), and an all‐atom explicit solvation method (C22 with TIP3P). The adsorption behavior of each peptide was characterized by the calculation of the potential of mean force as a function of peptide‐surface separation distance. The results from the C22/TIP3P model suggest that hydrophobic peptides exhibit relatively strong adsorption behavior, polar and positively‐charged peptides exhibit negligible to relatively weak favorable interactions with the surface, and negatively‐charged peptides strongly resist adsorption. Compared to the TIP3P model, the ACE and GBMV implicit solvent models predict much stronger attractions for the hydrophobic peptides as well as stronger repulsions for the negatively‐charged peptides on the CH3‐SAM surface. These comparisons provide a basis from which each of these implicit solvation methods may be reparameterized to provide closer agreement with explicitly represented solvation in simulations of peptide and protein adsorption to functionalized surfaces. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007