bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic liquefaction strength of sands
Authors: Mostaghel N. , Habibagahi K.
Published: March 2007

Through an energy approach, a model is proposed to predict the cyclic liquefaction strength of saturated sands in terms of their static shear strengths. Plots of cyclic liquefaction strength versus relative density and also versus modified standard penetration resistance are presented for various uniformity coefficients and different numbers of stress cycles. The predicted cyclic liquefaction strength values are converted to cyclic stress ratios and compare favourably with Seed's empirical correlations.
Axisymmetric seismic response of a thick circular plate supporting many rods by modal synthesis
Authors: Lee Teh Hwei
Published: March 2007

Dynamic response of a thick, horizontal, circular plate supporting a large number of slender rods subjected to uniform boundary motion in the vertical direction has been studied by synthesizing component modes of continuous substructures. The excitation considered corresponds to the vertical component of boundary movement produced by earthquake disturbances and the axisymmetric response problem was solved. Mindlin theory was used to formulate the component equations of the plate which is treated as the main component in a modal synthesis technique. The slender rods, which are attached vertically to the plate, are handled as branch components. Vibration modes of a classical thin plate were used as the initial displacement functions for the Mindlin plate. These functions were subsequently modified by a component mode improvement process to obtain plate modes. System modes were generated by combining the improved plate modes with component modes of rods. Numerical results for the natural frequencies and time‐history response of the coupled system are compared with those given by a three‐dimensional finite element method.
Generation of spectrum compatible accelerograms
Authors: Iyengar R. Narayana , Rao P. Narasimha
Published: March 2007

In this paper a new method is presented for generating earthquake accelerograms which have pre‐established response spectra. The non‐stationary random nature and other salient features of the accelerograms can be taken care of by the procedure developed. The method leads to a sample spectrum which lies above the given spectrum. The generation of records to suit several spectra simultaneously can also be handled by this approach. The method is detailed first. This is followed by several numerical examples.
Analysis of three‐dimensional strong ground motions along principal axes, San Fernando earthquake
Authors: Kubo Tetsuo , Penzien Joseph
Published: March 2007

An orthogonal set of principal axes is defined for earthquake ground motions. These principal axes are obtained such that the corresponding variances of motion have maximum, minimum and intermediate values and the covariances equal zero. This indicates that the corresponding components of motion along the principal axes are uncorrelated with respect to each other. Since real earthquake accelerograms are assumed to be reasonably well represented by Gaussian random processes, the three components of motion along the principal axes are statistically independent of each other.

Using these principal axes and applying the moving‐window technique to the ground accelerograms recorded during the San Fernando earthquake of 9 February 1971, time‐dependent characteristics of three‐dimensional ground motions along principal axes are determined. Results of the analysis indicate significant correlation between directions of principal axes and directions from the recording stations to the fault slip zone. It is concluded that three components of ground motion can be generated stochastically with statistical independence being maintained, provided they are assumed to be directed along principal axes.
Seismic motion and response prediction alternatives
Authors: Cornell C. Allin , Banon Hooshang , Shakal Anthony F.
Published: March 2007

Statistical methods are available which predict the maximum response of simple oscillators given the peak acceleration (Ap), peak velocity (Vp) or peak displacement (Dp) of seismic ground motions. An alternative parameter, namely an ordinate (or ordinates) of the Fourier amplitude spectrum of ground motion acceleration, FS(f), may in fact be a preferred predictor of peak response, especially in a frequency range close to f. Other statistical methods (attenuation laws) use distance R and other parameters such as magnitude (M), Modified Mercalli epicentral Intensity (Io) and Modified Mercalli site Intensity (MMI or Is) to predict spectral velocity (Sv(f)), etc. In using such approaches, it is most desirable to know the total uncertainty in the predicted peak response of the system given the starting parameter values. An extensive strong motion data set is used to study these questions, The most direct prediction models are found to be preferable (have lower prediction dispersion) but data may not be available in all regions to permit their use.
An analytical theory of resonant scattering of SH waves by thin overground structures
Authors: Mei Chiang C. , Foda Mostafa A.
Published: March 2007

Scattering of SH waves in a half‐space with simple overground structures is studied analytically. For two‐dimensional structures, such as shells, shear walls and a slab‐bridge over a river, the method of matched asymptotics is used for sinusoidal waves long compared to the thickness of the structures. Resonance features are deduced analytically and calculated numerically for various incidences and other parameters.
Free vibration of frame shear wall structures on flexible foundations
Authors: Cheung Y. K. , Swaddiwudhipong S.
Published: March 2007

The finite strip method is used to study the effect of an elastic foundation on the natural frequencies of coupled frame shear wall structures. The solid wall in the structure is divided into several strip elements, the column is treated as a line element and the effect of the connecting beams is dealt with through the compatibility matrices which transfer their structural properties to the adjacent strip or line elements. The comparison functions which satisfy the boundary conditions of being free at the top and being spring supported at the bottom are used for the displacement field in the longitudinal direction. A series of numerical examples is presented to show the accuracy and applicability of the proposed method.
The deployment of strong‐motion earthquake instrument arrays
Authors: Iwan Wilfred D.
Published: March 2007

The International Workshop on Strong‐motion Earthquake Instrument Arrays was held during 2‐5 May 1978 in Honolulu, Hawaii. The goal of the workshop was to develop a workable plan for the possible future deployment of dense strong‐motion arrays with primary emphasis on ground motion studies. Topics considered by the workshop included: favourable array locations, the design of arrays for source mechanism and wave propagation studies, the design of arrays for local effects studies, array construction and operation, and implementation. This paper gives a summary of the recommendations and conclusions of the workshop.
Ground motion at canyons of arbitrary shape under incident sh waves
Authors: Sánchez‐Sesma Francisco J. , Rosenblueth Emilio
Published: March 2007

A method for calculating the two‐dimensional scattering of incident SH waves by canyons of arbitrary shape is presented. The problem is formulated in terms of a Fredholm integral equation of the first kind with the integration path outside the boundary. Point‐source discretization and a least‐squares scheme are used. Numerical results are compared with the known analytic solution for a semi‐cylindrical canyon. Spatial variations of surface amplitudes are computed for triangular and half‐cycle sinusoidal canyons as well.
Earthquake response of underground pipelines
Authors: Hindy A. , Novak M.
Published: March 2007

Seismic response of underground pipelines is investigat́ed theoretically considering dynamic soil‐pipe interaction. A lumped mass model of the pipe is employed with the soil reactions derived from static and dynamic continuum theories. The soil is supposed to be homogeneous or composed of two different media separated by a vertical boundary. Axial and bending stresses in the pipe due to travelling waves are examined.

An extensive parametric study indicates that the axial stresses in the pipe are much higher than bending stresses. In a homogeneous medium, soil‐pipe interaction reduces the stresses in the pipe compared to those calculated ignoring interaction. In a soil composed of two different media, the pipe stresses are highest close to the boundary and can exceed those predicted neglecting interaction.
On the coupled torsional and sway vibrations of a class of shear buildings
Authors: Wittrick W. H. , Horsington R. W.
Published: March 2007

This paper is concerned with the free vibrations of a restricted class of multi‐storey shear buildings in which inertial coupling exists between the torsional and the two sway vibrations. The restrictions imposed are that (a) the shear centres of all storeys lie on a vertical straight line, (b) the principal axes of shear are in the same directions in all storeys, (c) the centres of mass of all floors lie on another vertical straight line, (d) the radius of gyration about the shear centre of every floor mass is the same and (e) the ratios of the two shear stiffnesses to the torsional stiffness do not vary from storey to storey.

In consequence of the last restriction it is proved that the 3n natural frequencies, normal modes and generalized masses, where n is the number of storeys, are expressible very simply in terms of products of the three natural frequencies, normal modes and generalized masses of the single‐storey, three‐dimensional building formed by removing everything above the first floor, with the n natural frequencies, normal modes and generalized masses of a certain n‐storey, two‐dimensional shear frame.

In the special case of a uniform building, a simple closed form solution, valid for any number of storeys, is given.
The Santa Barbara earthquake of 13 august, 1978
Authors: Miller Richard K.
Published: March 2007

Although the Santa Barbara earthquake was only a moderate seismic event, it was the most destructive earthquake in the United States in 1978 causing more than $7 million damage and at least 65 injuries. Reported Richter magnitudes ranged from 5–1 to 5–7, but estimates based on strong motion records yielded about 5–8. Due to the geologic features of the earthquake, the intensity of strong shaking was geographically asymmetrical, being much larger in the Goleta area north and west of the epicentre. Peak ground accelerations of 0–40 g were recorded near Goleta, while 0–23 g was recorded closer to the epicentre in Santa Barbara. The duration of strongest shaking was only about 2–3 s. The earthquake caused light cracking of shear walls in multi‐storey reinforced concrete structures, as well as damage to highway overcrossings, many mobile homes and to rooftop mechanical equipment. Presented in this paper are the results of preliminary investigations of the engineering features of this earthquake.
Dynamic response of single span highway bridges
Authors: Hutton S. G. , Cheung Y. K.
Published: March 2007

The dynamic response of single span simply supported bridge decks subjected to the passage of vehicles is examined. A modal analysis approach is adopted that is based upon a finite strip idealization of the deck. The vehicle is modelled as a rigid body supported at two points by a suspension idealization that accounts for the effect of tyre stiffness and the frictional nature of real suspension systems.

Results are presented for an orthotropic slab deck and a box girder deck that illustrate the effects of (i) the initial precompression of the suspension system as the vehicle enters the span, (ii) the ratio of the vehicle's natural frequency to that of the bridge deck and (iii) a bridge deck surface profile that is not perfectly horizontal.
Base isolation systems for earthquake protection of multi‐storey shear structures
Authors: Lee D. M. , Medland I. C.
Published: March 2007

This paper is a study of the effectiveness of a wide range of bilinear hysteretic isolation systems in shielding multistorey 2‐D shear structures from earthquake excitations. Important parameters of the isolation system are identified and their effect on structure response noted. It is shown that isolation systems can be constructed which allow the structure proper to remain purely elastic even during very strong ground motions. It is further shown that the shear responses and base displacements of structures on these isolation systems can be accurately estimated from elastic response spectra of the forcing earthquakes.

The philosophy of structure isolation is discussed and an introduction given to the physical devices currently available to provide it.
Site‐dependent critical design spectra
Authors: Wang P. C. , Yun C. B.
Published: March 2007

A new type of seismic response spectrum is presented. It is based on the concept of a ‘ critical excitation’ which is defined here as an excitation among a certain class of excitations that will produce the largest response peak for a design variable of interest. Site conditions, namely rock, stiff soil and deep cohesionless soil, are taken into account through the definition of the class of allowable excitations. The response spectra thus produced are compared with others that have been proposed or used in the past. Results indicate that they lead to realistic if somewhat conservative assessment of structural earthquake resistance. On the other hand, they are derived under assumptions that are rather well supported by seismological observation and avoid other questionable assumptions, especially those regarding the statistics of ground motions. The critical response spectra may thus inspire greater confidence on the part of their users than those currently proposed or relied on.
A decision‐theory methodology for the selection of buildings for strong‐motion instrumentation
Authors: Hart G. C. , Rojahn C.
Published: March 2007

Current projections indicate that six buildings per year will continue to be instrumented under the California Strong‐Motion Instrumentation Program for the next several decades. In order to select these buildings systematically for instrumentation, we have developed a methodology that incorporates the fundamental elements of decision theory. These elements include an identification of the types of buildings that should be instrumented, a definition of the expected severity of ground shaking at each possible building site along with the probability of occurrence, and a quantification of the relative value of obtaining a building‐response record for each building type. Using this information, we can apply decision theory to calculate the expected utility (degree of preference) of instrumenting buildings of a particular type at various sites. The sites are then ranked in order of preference for each building type. This procedure, developed for the California Strong‐Motion Instrumentation Program, can be extended to instrumentation programs in other areas.
Dynamic behaviour of a cable‐stayed bridge
Authors: Fleming John F. , Egeseli Engin A.
Published: March 2007

The dynamic response of a cable‐stayed bridge to seismic, wind and simulated traffic loads is discussed. The analysis procedure which is used considers non‐linear behaviour of the cables, caused by the variation in sag with tensile force, and non‐linear behaviour of the bending members, caused by the interaction of axial and bending deformations. It is concluded that the non‐linearity of the structure must be considered in determining the stiffness of the structure in the dead load deformed state. A linear dynamic analysis, however, starting from the dead load deformed state will give results within normally required design accuracy.
Seismic design response by an alternative SRSS rule
Authors: Singh Mahendra P. , Mehta K. B.
Published: March 2007

The square root of the sum of the squares (SRSS) procedure and its modified forms are often used to obtain seismic design response. The design inputs for such procedures are usually defined in terms of pseudo velocity or acceleration response spectra. Erroneous results have been obtained with these existing SRSS procedures, especially in the calculation of responses where high frequency effects dominate. Here an alternative SRSS procedure is developed using the so‐called mode acceleration approach of structural dynamics. The design input in this procedure is defined in terms of relative acceleration and relative velocity spectra. The relative spectra can be related to pseudo spectra. For a given number of modes to be included in the analysis the new SRSS rule proposed here will reduce the error due to the so‐called ‘missing mass’ effect and predict a more accurate response value than the rules which use pseudo spectra as input, for systems either with or without dominant high frequency mode effects.
Intensity of waves in a randomly non‐homogeneous layered medium
Authors: Hryniewicz Z.
Published: March 2007

The intensity of shear waves in the model of a multilayered stratum, the material properties of which are random functions, is considered. The solutions for displacements and stresses are obtained for one layer and then the formulation is extended to a multilayered stratum through transfer matrices. The solution for a random medium has been compared with the solution for the homogeneous medium. The analysis indicates that the stochastic inhomogeneities are likely to increase the damping in a significant way.
Some error bounds and numerical experiments in modal methods for dynamics of systems
Authors: Gladwell I. , Hanson P. M.
Published: March 2007

We present some error expressions for approximate modal solutions of viscously damped linear structural vibration equations; these approximations are calculated by a variety of modal techniques. Motivated by our numerical experience, we show the equivalence of some different modal solutions in the presence of classical damping and, in passing, we obtain a previously unremarked manifestation of this type of damping. We make some brief comments about obtaining error estimates and, finally, we show some numerical results for a standard test problem which illustrate properties of the modal solutions.
Dynamic response of pipelines to moving loads
Authors: Datta S. K. , Chakraborty T. , Shah A. H.
Published: March 2007

Vibration of buried pipelines induced by moving axial and radial loads has been studied in this paper. A thin shell model has been used for the pipeline, which is assumed to be lying in an infinite isotropic homogeneous elastic medium. In order to allow for the possible motion of the pipe out of phase with the surrounding ground a very thin layer of viscoelastic material is assumed to separate the pipe from the ground. Calculations indicate the presence of the interfacial viscoelastic layer does not influence the pipe response in a significant manner. So all the numerical results presented here are for the case when the pipe is assumed to be perfectly bonded. These show that the maximum pipewall displacements and stresses occur in a soft soil at long wavelengths.
On the effective seismic input for non‐linear soil‐structure interaction systems
Authors: Bielak Jacobo , Christiano Paul
Published: March 2007

Two equivalent semi‐discrete formulations are presented for the problem of the transient response of soil‐structure interaction systems to seismic excitation, considering linear behaviour of the soil material and arbitrary non‐linear structural properties. One formulation results in a direct method of analysis in which the motion in the structure and the entire soil medium, rendered finite by an artificial absorbing boundary, is determined simultaneously. The other represents a substructuring technique in which the structure and the soil are analysed separately.

The forces induced in the discretized system by the incident seismic motion are obtained as part of the general formulation by using the free‐field motion of the unaltered soil as the earthquake input. It is shown that these forces act within the soil region in the direct method, but only on the soil‐structure interface in the substructure formulation. Both sets of forces, however, involve only the displacements and tractions acting on the fictitious surface in the unaltered (linear) soil which coincides with the soil‐structure interface of the complete system. It is shown, further, that the free‐field displacements alone define a minimal set of data for evaluating the seismic response of the structure, since the tractions and displacements on that surface are interrelated. In practice, the minimal set must be obtained by extrapolating the available information, as the free‐field ground motion at a site is usually specified at a single reference point.
Modal decomposition method for stationary response of non‐classically damped systems
Authors: Igusa Takeru , Kiureghian Armen Der , Sackman Jerome L.
Published: March 2007

The stationary response of multi‐degree‐of‐freedom non‐classically damped linear systems subjected to stationary input excitation is studied. A modal decomposition procedure based on the complex eigenvectors and eigenvalues of the system is used to derive general expressions for the spectral moments of response. These expressions are in terms of cross‐modal spectral moments and explicitly account for the correlation between modal responses; thus, they are applicable to structures characterized with significant non‐classical damping as well as structures with closely spaced frequencies. Closed form solutions are presented for the important case of response to white‐noise input. Various quantities of response of general engineering interest can be obtained in terms of these spectral moments. These include mean zero‐crossing rate and mean, variance and distribution of peak response over a specified duration. Examples point out several instances where non‐classical damping effects become significant and illustrate the marked improvement of the results of this study over conventional analysis based on classical damping approximations.
Hazardous buildings: Aspects of the los angeles earthquake problem
Authors: Lee D. M. , Shepherd R.
Published: March 2007

In recognition of the life‐threatening dangers posed by many thousands of buildings completed prior to the requirement for provision of any specific earthquake resistance, in 1981 the City of Los Angeles adopted a seismic safety ordinance requiring the upgrading of these buildings to predetermined engineering standards. Various methods of modifying such structures, which are characteristically of unreinforced multi‐storey masonry bearing wall configuration with interior wood framing, are summarized in this paper. In addition to presenting typical structural details, some of the socio‐economic and financial aspects of the earthquake hazard mitigation programme are discussed.
Transient flexural vibrations of a timoshenko column supported by an elastic half‐space
Authors: Wada H.
Published: March 2007

Transient flexural vibrations of an elastic column supported by an elastic half‐space are investigated analytically under the condition that an arbitrarily shaped free‐field lateral acceleration is given as an input. Applying the Timoshenko theory to the column and making use of Laplace transformations with respect to time and numerical inverse Laplace transformations, the time histories of the column free end acceleration are presented. Numerical results obtained from the Timoshenko theory are compared with those of a previous paper1 (applying the Bernoulli‐Euler theory to the column), and the effects of column slenderness and foundation stiffness on the transient flexural vibrations of the column are clarified.
Dynamic response of twin circular tunnels due to incident SH‐waves
Authors: Balendra Thambirajah , Thambiratnam David P. , Koh Chan Ghee , Lee Seng‐Lip
Published: March 2007

The steady‐state solution for two parallel under ground tunnels of circular cross‐section subjected to incident plane harmonic SH‐waves is obtained in closed form, by using the method of wave function expansion. The image technique is employed to account for the reflection of waves at the ground surface. Numerical studies are carried out to determine the influence of spacing between the tunnels on the shear stresses in concrete and steel linings.
The optimum design of a base isolation system with frictional elements
Authors: Constantinou Michalakis C. , Tadjbakhsh Iradj G.
Published: March 2007

A linear multistorey structure with a seismic base isolation system consisting of rubber bearings and frictional elements is considered. The non‐linear equations of motion are derived for the first mode vibration and the stochastic response to a white noise ground acceleration is determined. Based on this response, suitable objective functions are defined and the optimum design of the isolation system is performed. It is shown that a small amount offriction increases the effectiveness of the system compared with the same system but without frictional elements.
Soil‐structure interaction effects on the steady‐state response of torsionally coupled buildings
Authors: Tsicnias T. G. , Hutchinson G. L.
Published: March 2007

The work presented in this paper investigates the effect of the foundation flexibility on the coupled lateral‐torsional response of single‐storey buildings excited by translational ground motion. The eccentricity between the centre of mass and the centre of resistance is considered to be the only cause of coupling of the lateral and torsional response of the building.

The study is confined to the steady‐state response of rigidly supported and flexibly supported torsionally coupled buildings subjected to harmonic free‐field ground displacement perpendicular to the direction of the eccentricity. In the case of the flexibly supported building the foundation medium is assumed to be an elastic homogeneous isotropic half‐space.

The effect of the controlling parameters on lateral‐torsional coupling is investigated. It is concluded that for a particular range of values of these parameters (representing most cases of actual buildings) their effect on the coupling of lateral and torsional response is not qualitatively affected by increases in the flexibility of the foundation medium.
Finite element versus simplified methods in the seismic analysis of underground structures
Authors: Gómez‐massó Alberto , Attalla Ibrahim
Published: March 2007

Seismic analysis of buried tunnels is considered herein. A comparison of results is carried out between a detailed finite element analysis and several simplified models for hand calculation. The finite element analysis is conducted by superimposing the free field motions and the interaction motions. The latter are calculated in a plane strain geometry taking into account the influence of adjacent structures with an approximation for 3‐D effects and for soil non‐linearities. Simplified models give, in general, conservative results, although better approximations are obtained by modelling the tunnel bends, where stress concentration occurs.
Evaluation of deformation of tunnel structure due to Izu‐Oshima‐Kinkai earthquake of 1978
Authors: Kawakami Hideji
Published: March 2007

Due to the Izu‐Oshima‐Kinkai earthquake of 1978, the Inatori tunnel, a single‐track railway tunnel in Japan, was severely damaged. This damage was mainly caused by the main fault and a subsidiary fault which is estimated to have traversed the tunnel. The objective of this paper is to evaluate the performance of available mathematical models of earthquake wave propagation by taking advantage of the actual damage data of this tunnel. This paper has also the purpose of contributing to the earthquake‐resistant design procedure of the tunnel in the source region by estimating its deformation using the fault mechanical model. In this paper using a set of fault parameters previously proposed by seismologists for the Izu‐Oshima‐Kinkai earthquake, the longitudinal, transverse and vertical displacements of the tunnel axis are computed. These computed results are then compared with the surveyed residual deformation. For each of three deformation components a similar trend can be recognized, and the comparison indicates that a reasonably good correlation exists between these surveyed and computed displacements.
Dynamic‐stiffness matrix of soil by the boundary‐element method: Embedded foundation
Authors: Wolf John P. , Darbre Georges R.
Published: March 2007

Green's influence functions are derived for a linearly distributed load acting on part of a layered elastic halfplane on a line which is inclined to the horizontal. Using these Green's functions as fundamental solutions in the boundary‐element method, the dynamic‐stiffness matrices of the unbounded soil with excavation, of the excavated part and of the free field are calculated. The indirect boundary‐element method using distributed loads and no offset leads to more accurate results than the weighted‐residual technique and the direct boundary‐element method. At the natural frequencies of the undamped excavated part built‐in along the structure‐soil interface, the spring coefficients associated with the dynamic‐stiffness matrices of the excavated part and of the free field will become infinite. If the dynamic‐stiffness matrix of the soil with excavation is calculated as the difference of that of the free field and that of the excavated part, the difference of two large numbers will arise in the vicinity of these frequencies. A consistent discretization must then be used. In particular, the dynamic‐stiffness matrix of the embedded part cannot be determined by the finite‐element method in this case. A parametric study is performed for the dynamic‐stiffness matrix of the free field for a rectangular foundation embedded in a halfplane and in a layer built‐in at its base; the aspect ratio and the damping of the soil are varied.
Dynamic phenomena in ropeways after a haul rope rupture
Authors: Portier B.
Published: March 2007

The aim of the work presented here is to provide an accurate prediction of the dynamical behaviour of reversible aerial ropeways. A mechanical and numerical model is developed in order to check the safety of any such ropeway after a haul rope rupture.

The whole installation (including carriers, counterweights and ropes) is first given an initial position. The model then simulates the disappearance of some cables and counterweights, and evaluates the subsequent displacements of the remaining parts, excluding track ropes. The model uses very simple first‐order finite elements, accounting for non‐linear effects caused by large displacements. The numerical integration is very efficient, and suits the capabilities of small microcomputers; it does not require matrix inversions, nor stiffness matrix evaluations.

A full‐scale experiment has recently been carried out on a ropeway in the French Alps. If a simple kind of viscous damping is accounted for, numerical and experimental results compare with a reasonable accuracy. The present model is now in use for design and control of actual ropeway equipment.
Vibrations of beams with an absorber consisting of a viscoelastic solid and a beam
Authors: Yamaguchi H. , Saito H.
Published: March 2007

This paper considers the response of a beam with a dynamic vibration absorber, which consists of a viscoelastic solid and a double‐cantilever viscoelastic beam, attached to the centre of the main beam. The ends of the main beam are built in and excited sinusoidally by the base motion. The transfer matrix method is used in the analysis. The displacement transmissibility, i.e. the ratio of the displacement at the centre of the main beam to that of the base is investigated in the numerical example. It is shown that the present absorber is effective to suppress several resonances of the main beam simultaneously by only one compact device. Values of the optimum tuning design parameters are presented in the numerical example.
Some methods for the analysis of equipment‐structure interaction
Authors: Ingham Tim J. , Sackman Jerome L.
Published: March 2007

We present some numerical methods which simplify the analysis of equipment‐structure systems composed of an equipment component which is light with respect to the structure component. We consider completely general forms of equipment‐structure interaction. In particular, we consider that an arbitrary number of natural frequencies of the equipment and the structure are nearly equal (or equal) to each other.

We show that this coincidence of natural frequencies implies that the equipment‐structure system will itself have several closely spaced natural frequencies. The essence of equipment‐structure interaction is the formation of beats, with slowly varying amplitude in each degree of freedom, between these natural frequencies‐at least in response to a δ‐function ground motion.

We derive some differential equations, the solutions of which are a slowly varying envelope function (a vector) which yields the above slowly varying amplitudes. It is obtained by numerical integration using some conventional, but modified, methods and using a step size appropriate to capture its slowly varying nature.

This envelope function defines the response to a δ‐function ground motion. We show how it may be combined with the properties of an arbitrary ground motion (acceleration record or response spectrum) to yield the response to such a ground motion.
Reliability of structures subjected to differential fault slip
Authors: Kiremidjian Anne S.
Published: March 2007

This paper presents a method for determining the probabilities of fault displacement at specific locations on a fault of finite length. The method is further extended to include a procedure for estimating the maximum strain, stress and axial tensile force in a pipe crossing a fault. With this procedure, estimates are also obtained for the curved lengths of the pipe. The feasibility of the method is demonstrated through a specific example. For that purpose an X‐60 pipe crossing the San Andreas fault in Northern California is used. The procedure is particularly useful in risk consistent design and can be readily extended to structures other than underground pipes.
Free vibration of asymmetric shear wall‐frame buildings
Authors: Balendra Thambirajah , Swaddiwudhipong Somsak , Quek Ser‐Tong , Lee Seng‐Lip
Published: March 2007

The Galerkin method of weighted residuals is used to determine the frequencies and associated mode shapes of asymmetric shear wall‐frame structures. The governing equations are formulated using the continuum approach by idealizing the structure as a shear‐flexure beam. Varying properties along the height of the building are considered. The effect of translational, rocking and torsional flexibilities of the foundation on the natural frequencies is also investigated. The method presented herein utilizes polynomial and transcendental displacement functions, and is found to be simple, versatile and efficient.
Earthquake analysis of concrete gravity dams including reservoir bottom absorption and dam‐water‐foundation rock interaction
Authors: Fenves Gregory , Chopra Anil K.
Published: March 2007

The available substructure method for the earthquake analysis of concrete gravity dams, including the dynamic effects of the impounded water and the flexible foundation rock, is extended to include the effects of alluvium and sediments invariably present at the bottom of actual reservoirs. Modelled approximately by a reservoir bottom that partially absorbs incident hydrodynamic pressure waves, these effects are incorporated into the continuum solution for the hydrodynamic pressure. The dam‐water‐foundation rock system is idealized as a two‐dimensional system and analysed under the assumption of linear behaviour.

An example earthquake analysis is presented to demonstrate the results obtained from the analytical procedure. Computation times for several cases illustrate the efficiency of the analytical procedure. In particular, the additional computation time required to include reservoir bottom absorption is shown to be very small.
Seismic response of base‐isolated structures with vertical‐rocking coupling
Authors: Pan Tso‐Chien , Kelly James M.
Published: March 2007

A base‐isolated building is liable to have a small horizontal eccentricity between the centre of mass of the superstructure and the centre of rigidity of the supporting bearings. In seismic analysis, the structure is modelled as a rigid block with tributary masses supported on massless elastomeric rubber bearings placed at a constant elevation below the centre of mass. This simplified system has three degrees of freedom: two translations and one rotation in the vertical plane.

The investigation of the dynamic behaviour of a base‐isolated building is carried out for both the detuned and the perfectly tuned cases. In the detuned case, the natural frequencies of the system are assumed to be well separated. In the perfectly tuned case, the uncoupled rocking frequency is assumed to be identical to the vertical translational frequency, which may result from an unusual mass distribution and/or an extreme aspect ratio of the superstructure. Perturbation methods are implemented in finding the dynamic characteristics for both cases. However, the dynamic response of the perfectly tuned case is the major concern in this investigation.

The Green's functions for the displacement response of the three‐degree‐of‐freedom system are derived for both the undamped and damped conditions. The response spectrum modal superposition method is used in estimating the maximum acceleration response. A simple method, accounting for the effect of closely spaced modes, is proposed for combining modal maxima and results in an approximate solution corresponding to a single‐degree‐of‐freedom system. This approximate solution may be used for the preliminary design of a base‐isolated structure.

Numerical results for a base‐isolated building subjected to the vertical component of the El Centro earthquake of 1940 were carried out for comparison with these analytical results. The proposed modal combination method showed superiority over the conventional Square Root of the Sum of the Squares method in estimating maximum responses. The results also indicated that the approximate single‐degree‐of‐freedom system yields accurate estimations.

It is shown that the effect of rocking coupling on the vertical response of base‐isolated structures subjected to transient loadings, such as earthquake motions, can generally be neglected as a result of the combined effects of the time lag between the maximum translational and rotational responses and the influence of damping in the isolation system, which for elastomeric bearings can be as high as 8 to 10 per cent of critical.
Dynamic performance analysis of novel unified power flow controller with computer simulation and scaled‐model experiment
Authors: Han Byung M. , Ledwich Gerard
Published: March 2007

This paper describes dynamic performance analysis of Unified Power Flow Controller (UPFC) composed of cascaded H‐bridge and single‐phase multi‐winding transformers for isolation. The operational characteristic was analyzed through simulations with PSCAD/EMTDC, and experimental works with a scaled model. The UPFC proposed in this paper can be directly connected to the transmission line without series injection transformers. It has flexibility to expand the operation voltage by increasing the number of H‐bridges. Copyright © 2007 John Wiley & Sons, Ltd.
Nuclear actin is involved in the regulation of CSF1 gene transcription in a chromatin required, BRG1 independent manner
Authors: Song Zhaoxia , Wang Min , Wang Xiaoguang , Pan Xuefang , Liu Wenguang , Hao Shui , Zeng Xianlu
Published: March 2007

Actin is an important protein in nucleus and has been implicated in transcription, however, the mechanism of its function in transcription is still not clear. In this article, we studied the role of actin in the regulation of human CSF1 gene transcription. Our results showed that nuclear actin stimulates the activity of CSF1 promoter, and the role in augmenting CSF1 gene transcription requires the formation of chromatin and Z‐DNA structure. The ATP binding motifs of nuclear actin are essential for its function in regulating CSF1 gene transcription, and upon actin overexpression, there is an increase in the ATPase activity of nuclear proteins. Further investigation revealed that nuclear actin regulates CSF1 gene transcription in a BRG1 independent manner. Together, these original results have provided evidence for further understanding the mechanism of nuclear actin in regulating gene transcription. J. Cell. Biochem. 102: 403–411, 2007. © 2007 Wiley‐Liss, Inc.
Multispectral fluorescence lifetime imaging by TCSPC
Authors: Becker Wolfgang , Bergmann Axel , Biskup Christoph
Published: March 2007

We present a fluorescence lifetime imaging technique with simultaneous spectral and temporal resolution. The technique is fully compatible with the commonly used multiphoton microscopes and nondescanned (direct) detection. An image of the back‐aperture of the microscope lens is projected on the input of a fiber bundle. The input of the fiber bundle is circular, and the output is flattened to match the input slit of a spectrograph. The spectrum at the output of the spectrograph is projected on a 16‐anode PMT module. For each detected photon, the encoding logics of the PMT module deliver a timing pulse and the number of the PMT channel in which the photon was detected. The photons are accumulated by a multidimensional time‐correlated single photon counting (TCSPC) process. The recording process builds up a four‐dimensional photon distribution over the times of the photons in the excitation pulse period, the wavelengths of the photons, and the coordinates of the scan area. The method delivers a near‐ideal counting efficiency and is capable of resolving double‐exponential decay functions. We demonstrate the performance of the technique for autofluorescence imaging of tissue. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Ultrastructure of the Male Reproductive System of Cotesia vestalis (Hymenoptera: Braconidae) with Preliminary Characterization of the Secretions
Authors: Huang Fang , Yu Rui‐Xian , Chen Xue‐Xin
Published: March 2007

The morphology and ultrastructure of testes and accessory glands along with the characterization of their secretions were investigated for a braconid species Cotesia vestalis (Hymenoptera: Braconidae) using light and electron microscopes. The male internal reproductive system of this species is distinguished by a pair of testes, one vas deferens, and a pair of male accessory glands. The testes are separate, and the accessory glands are oval and not fused. It was observed that the secretory cells of testes have characteristic smooth and rough endoplasmic reticulum, and that the cytoplasm is filled with an array of granule droplets usually of two to three types. The secretory cells in the case of accessory glands are typified by the presence of microvilli on their apical cell surfaces and numerous mitochondria in their cytoplasm. SDS‐PAGE profile when performed depicted a similarity in most bands of the secretions from both testes and accessory glands, except for four proteins of which two were present only in testes, while the other two only appeared in accessory glands. Their molecular weights were 117 and 55 kDa for testes and 196 and 30 kDa for accessory glands, respectively. This study gives new insights into the intriguing features of male internal reproductive system and it especially constitutes the first report of its kind about the secretion properties of these organs in C. vestalis. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
FRET measurements on fuzzy fluorescent nanostructures
Authors: Caorsi V. , Ronzitti E. , Vicidomini G. , Krol S. , McConnell G. , Diaspro A.
Published: March 2007

In the last decade, fluorescence resonance energy transfer (FRET) has become a useful technique for studying intermolecular interactions applied to the analysis of biological systems. Although FRET measurements may be very helpful in the comprehension of different cellular processes, it can be difficult to obtain quantitative results, hence the necessity of studying FRET on controllable systems. Here, a fuzzy nanostructured system called a nanocapsule is presented as a nanometric‐device allowing distance modulation, thus preserving photophysical properties of fluorescent dyes and exhibiting good potential features for improving quantitative FRET analysis. We evaluated the behavior of such a sample using four FRET methods (three of them based on steady‐state fluorescence and one using lifetime measurements). Within some limitations that can be overcome, these nanodevices have the potential to serve as a benchmark system for characterizing new FRET couples and to develop quantitative approaches for FRET analysis. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Accumulation of Triosephosphate Isomerase, with Sequence Homology to β Amyloid Peptides, in Vessel Walls of the Newborn Piglet Hippocampus
Authors: Kusaka Takashi , Ueno Masaki , Miki Takanori , Kanenishi Kenji , Nagai Yukiko , Huang Cheng‐Long , Okamoto Yasuo , Ogawa Takafumi , Onodera Masayuki , Itoh Susumu , Akiguchi Ichiro , Sakamoto Haruhiko
Published: March 2007

We investigated whether β‐amyloid (Aβ)‐like immunoreactivity was seen in the brains of newborn piglets. The immunoreactivity for Aβ(1‐42) and Aβ(1–40) proteins, but not Aβ precursor protein, was present in CD68‐positive perivascular cells of the hippocampus and in parts of the meninges. It was colocalized with immunoreactivity for receptor for advanced glycation end product and tumor necrosis factor‐α. The protein with a molecular mass of 27 kDa, which was recognized by the Aβ antibodies, was identified as triosephosphate isomerase (TPI) with sequence homology to Aβ peptides by N‐terminal amino acid sequencing, mass fingerprint analysis using matrix‐associated laser desorption/ionization mass spectrometry, and Western blotting. Western blotting assay also revealed that detectable expression of Aβ proteins were not seen in the piglet brains. These findings indicate that TPI with sequence homology to Aβ peptides accumulates in perivascular cells of the microglia/macrophage lineage located around arterial vessels of the newborn piglet hippocampus. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.