bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic stability characteristics of liquid‐filled shells
Authors: Uras Rasim Aziz , Liu Wing Kam
Published: April 2007

A Galerkin Finite Element formulation for the dynamic stability analysis of liquid‐filled shells is given in this paper. The coupling among the axial and circumferential modes is investigated. The dynamic stability characteristics of two liquid‐filled storage tanks subjected to vertical, horizontal and rocking seismic excitations are presented. It is shown that a tall tank tends to buckle at distinct frequencies; and for cos θ‐type ground excitation, cos 2θ, cos 3θ and cos 4θ are the dominant modes of failure. On the other hand, in a broad tank, buckling regions overlap each other. In particular, for cos θ‐type ground excitation, the dominant buckling modes are cos 6θ to cos 9θ, and also cos 12θ to cos 14θ.
Uniform magnitude re‐evaluation of European earthquakes associated with strong‐motion records
Authors: Ambraseys N. N.
Published: April 2007

This paper presents uniformly calculated surface‐wave magnitudes of over 400 earthquakes in the European area and adjacent regions associated with strong‐motion recordings. Seismic moments and body‐wave magnitudes are estimated also, so that they may be used in the derivation of attenuation laws. Using a more complete set of data the attenuation law derived for western North American earthquakes is modified for surface‐wave magnitudes.
Non‐linear earthquake‐response analysis of long‐span cable‐stayed bridges: Theory
Authors: Nazmy Aly S. , Abdel‐Ghaffar Ahmed M.
Published: April 2007

The non‐linear dynamic analysis of three‐dimensional long‐span cable‐stayed bridges when subjected to seismic loading is formulated. All possible sources of non‐linearity, such as cable sag, axial force‐bending moment interaction in bridge towers and girders and change of geometry of the whole bridge due to large displacements are considered in the analysis. Both cases of uniform and multiple‐support seismic excitations are considered in the non‐linear formulation of the problem. A tangent stiffness, iterative procedure is utilized to capture the the non‐linear seismic response. The non‐linear equations of motion are solved using a step‐by‐step integration technique in the real displacement coordinate space as well as in the modal coordinate space to save computational time.
Non‐linear earthquake‐response analysis of long‐span cable‐stayed bridges: Applications
Authors: Nazmy Aly S. , Abdel‐Ghaffar Ahmed M.
Published: April 2007

The dynamic non‐linear behaviour of three‐dimensional long‐span cable‐stayed bridges under seismic loadings is studied. The cases of multiple‐support as well as uniform seismic excitations of these long and flexible structures are considered. Different sources of non‐linearity for such bridges are included in the analysis, as outlined in the companion paper. In this accompanying analysis a tangent stiffness iterative procedure is utilized to estimate the non‐linear seismic response. Numerical examples are presented in which a comparison between a linear earthquake‐response analysis (based on the utilization of the tangent stiffness matrix of the bridge at the dead‐load deformed state which is obtained from the geometry of the bridge under gravity load conditions) and a non‐linear earthquake response analysis using the step‐by‐integration procedure is made. In these examples two three‐dimensional bridge models representing recent and future trends in cable‐stayed bridge design are utilized. The study sheds some light on the salient features of the seismic analysis and design of these long contemporary bridges. In addition, parameters affecting the seismic response of these bridges are discussed: other factors considered are non‐linearity, uniformity and spatial variation of ground motion inputs and structural configuration.
Stochastic response of suspension bridges to earthquake forces
Authors: Dumanoglu A. A. , Severn R. T.
Published: April 2007

The purpose of the paper is to study the applicability of stochastic methods for determining the response in the vertical plane of long‐span bridges to earthquakes. The bridges are of the modern type, with flexible towers, box‐decks and inclined hangers, Humber and Bosporus being used as the main examples, although some useful information is obtained by studying a small suspension footbridge. The input ground acceleration is that of the Pacoima Dam record of the 1971 San Fernando event, but use is also made of filtered white noise.

Because the stochastic approach is essentially an attempt to abstract usable information which could otherwise be obtained from a lengthy time‐history approach, the procedure adopted here is to compare the same parameters obtained in these two ways, as far as possible. In particular, the maximum values of displacements and bending moments are considered.

The essential question to be answered is whether the short length of earthquake records, coupled with the large natural periods of vibration of long‐span bridges, allows sufficient response information to be generated to make statistical parameters meaningful. The short‐span (50 m) footbridge gives no cause for concern here, but the detailed comparison with time‐history solutions shows that the stochastic approach for both Bosporus and Humber has to be cautiously assessed, particularly if some trailing zeros are not added to the earthquake record. However, general conclusions are not made, because only one earthquake record has been used.
Response of indeterminate two‐span beam to spatially varying seismic excitation
Authors: Harichandran Ronald S. , Wang Weijun
Published: April 2007

In order to examine the effect of the spatial variation of ground motion on the response of an indeterminate structure, the stochastic responses of a two‐span beam to spatially varying support excitations are analysed. A space‐time earthquake ground motion model that accounts for both coherency decay and seismic wave propagation is used to specify the support motions, and the results are compared with those for various simplified excitations that are commonly used in practice. The response is computed through a linear random vibration approach with the structure being modelled by finite elements. The results of the study indicate that, even for moderate lengths, the effect of the spatial variation of ground motion can be significant. The assumption of fully coherent support motions (same excitations at all supports or delayed excitations allowing only for wave propagation) may be overconservative for some beams and unconservative for others.
Mechanics and performance of a tied‐back wall under seismic loads
Authors: Neelakantan G. , Budhu Muniram , Richards R.
Published: April 2007

In this paper the stability of a tied‐back wall subjected to seismic loads is analysed for a predetermined mode of failure (rotation about the top of the wall) and the analysis is compared with data from tests on this type of wall using the seismic simulator at the State University of New York at Buffalo. We carried out a pseudo‐static analysis of the problem using the Mononobe‐Okabe earth pressure coefficients, wherein the dynamic effects due to the seismic loading are converted into equivalent static loads. The acceleration ratio at which the wall fails by rotation about the top was obtained by considering the moments due to the various lateral earth pressure resultants and the inertial forces induced in the soil due to the seismic loading.

We found that the presence of wall friction on the passive side significantly enhances the stability of the flexible retaining wall under seismic loads. Thus, flexible retaining walls supporting dry cohesionless soil can be very efficient during earthquakes. Under moderate earthquakes, an increase in the depth of embedment increases the dynamic factor of safety significantly. However, beyond a certain acceleration ratio for a soil with a particular value of ø, any increase in the depth of emdedment has no effect in impeding failure, irrespective of any change in the geometry of the system. Seismic design charts are presented to evaluate the stability of, and to design, flexible retaining walls embedded in dry cohesionless soils under seismic loading.
Structural response to non‐stationary multiple‐support random excitation
Authors: Perotti Federico
Published: April 2007

The seismic behaviour of large‐size structures subjected to multiple‐support excitation is studied by means of a random vibration approach. Ground motion is modelled as a non‐stationary stochastic process having an evolutionary spectral density. To describe the spatial variability of the input motion a model is adopted which accounts for finite propagation velocity and for loss of correlation as a function of distance and frequency.

Structural analysis is entirely performed in the frequency domain and full advantage is taken of FFT properties and capabilities. An example is given regarding the behaviour of a 800 m long viaduct. Results are shown in terms of response evolutionary spectral density, variance and reliability with respect to a fixed threshold.
Seismic damage to segmented buried pipelines
Authors: Elhmadi Kamel , O'Rourke Michael J.
Published: April 2007

Seismic damage to segmented buried pipelines is investigated in this paper. Information on their performance during past earthquakes is reviewed briefly. An analytical model for evaluating the response of long straight runs of segmented buried pipelines to seismic wave propagation is presented. It takes into account the non‐linearity as well as the variability of the system characteristics. Also, results from laboratory tests by others are used to establish the relative joint displacement which leads to leakage. These two elements are combined to predict the damage ratio (number of leaks per kilometre) for cast iron pipes with lead caulked joints subject to a joint pull‐out failure mode.
Amplification of elastic waves by a three dimensional valley. Part 1: Steady state response
Authors: Mossessian Tomi K. , Dravinski Marijan
Published: April 2007

Steady state scattering of incident P, SV, SH and Rayleigh waves by general non‐axisymmetric three dimensional dipping layers is investigated by using an indirect boundary integral equation method. Material of the half‐space and the layer is assumed to be linear, weakly anelastic, homogeneous and isotropic.

Systematic comparisons between three dimensional and two dimensional models demonstrate that the validity of a two dimensional approximation for a given basin shape may be affected strongly by changes in azimuthal angle of incidence, type of incident wave and frequency. The discrepancies of two dimensional modelling appear to be much more pronounced for the case of an incident SH wave. Another important feature of the results is the existence of strong coupling between P/SV and SH modes, which has no correspondence in two dimensional models. Such off‐azimuthal mode conversions are particularly strong for an incident SH wave.
Seismic analysis of non‐linearly base‐isolated soil‐structure interacting reactor building by way of the hybrid frequency‐time‐domain procedure
Authors: Darbre Georges R.
Published: April 2007

The seismic analysis of a reactor building on a sliding‐type base isolation is performed by way of the hybrid frequency‐time‐domain procedure. The frequency dependence of the foundation stiffness coefficients is duly accounted for in the analysis, although the problem is non‐linear. The response results are shown to be reliable by way of comparison with the results of a time‐stepping algorithm in the specialized case of constant foundation stiffness coefficients. The fact that such an analysis can be performed is an outstanding result, particularly when considering that no difficulties are encountered in the implementation and in the calculation. The flow chart used to implement the procedure is presented in the paper.

The reactor building is analysed for three different sites with each site having three sets of material properties. It appears that the structural response is not strongly affected by the frequency dependence of the foundation stiffness coefficients. This also holds true as far as the response of equipment attached to the superstructure is concerned. For all practical purposes this frequency dependence may be disregarded in favour of constant spring and damping coefficients.
Estimation of shear moduli and damping factors of earth dam materials
Authors: Lin Jeen‐Shang , Chao Biing‐Kuen
Published: April 2007

Abdel‐Ghaffar and Scott developed a procedure for extracting the shear moduli and damping factors of soils based upon strong motion records from earth dams. It is a very efficient procedure for earth dams that exhibited predominantly first mode response along the upstream‐downstream direction. In their approach, they employed digital band‐pass filters on the crest and abutment acceleration records, and constructed the hysteresis loops of soils by treating these filtered records as the input‐output to a non‐linear SDOF structure. In the process an important superposition assumption was implicitly introduced. This study looked into the implications of this linear superposition assumption on presumed nonlinear systems. Specifically, numerical simulations were conducted in finding out whether or not such a procedure is capable of extracting a known input dynamic behaviour of soils. It was found that the hysteresis loops were generally distorted, and to minimize errors only those loops of larger strain amplitudes should be used. Simple guidelines were suggested accordingly. Applications to real records from two dams were carried out following the proposed guidelines. Results of such applications were explored.
Correlation of predicted seismic response using hybrid modelling with EPRI/TPC lotung experimental data
Authors: Chen Cheng‐Hsing , Lee Yang‐Jye , Jean Wen‐Yu , Katayama Ikuo , Penzien Joseph
Published: April 2007

The hybrid modelling method is presented herein along with the equivalent linearization method to take account of the strain‐dependent non‐linearity of soils in a soil‐structure interaction (SSI) seismic analysis. A refined substructuring of the soil‐structure system is utilized and two separate analyses are made to determine the soil free‐field and SSI motions induced by earthquake excitation. This method is used to predict the seismic response of a 1/4‐scale containment model built in the seismically active area of Lotung, Taiwan. The results obtained show excellent correlation with the field test results.
Simplified mechanical subgrade model for dynamic response analysis of shallow foundations
Authors: Nogami Toyoaki , Leung Ming Biu
Published: April 2007

Baranov proposed an approach for the treatment of the subgrade in the dynamic response analysis of a rigid foundation which is partially embedded. The approach is based on a Winkler approximation together with wave equation solutions developed for simplified conditions. The paper extends and modifies Baranov's approach so as to be applicable to surface foundation problems, by introducing an internal coupling mechanism. Closed form expressions are presented for the steady state harmonic responses of a massless rigid footing and an elastic beam on the surface of the presented subgrade model. These expressions can accommodate the inhomogeneity of the subgrade in a straightforward manner. The model is found to perform well in reproducing the continuous subgrade medium behaviour. The dynamic responses of structures are often highly dependent on the subgrade modelling and therefore great caution is needed in modelling the subgrade.
M computed from strong motion accelerograms recorded in Yugoslavia
Authors: Lee V. , Trifunac M. , Herak M. , Živčič M. , Herak D.
Published: April 2007

It is shown that the new definition1 of strong motion local magnitude M leads to stable estimates of magnitudes for earthquakes in Yugoslavia, with epicentral distances R <100 km and for 2.5 < M < 6.5. Tables with magnitudes computed using this new procedure are presented for all earthquakes contributing to the strong motion accelerogram files in EQINFOS for Yugoslavia.2 The similarity of our findings with the analogous analyses for California suggests new possibilities for relative calibration between various local magnitude scales, which are used in southeastern Europe, and ML in California.
Sliding‐uplifting response of rigid blocks to base excitation
Authors: Andreaus Ugo
Published: April 2007

In the present paper a two‐degree‐of‐freedom system is considered which allows the simulation of rigid blocks uplifting and sliding on frictional foundations; the monolateral constraint between block and base is schematized by means of a joint model, which allows the contact problem to be discretized. The joint model is governed by normal and shear constitutive laws, which have been derived by the phenomenological behaviour of stone blocks and rock joints, as given by rock mechanics. Furthermore, a numerical procedure has been developed in order to solve the non‐linear equations governing the motion of the block‐base system, and to analyse the dynamic response of this system under seismic excitation; particular attention has been paid to the influence of the vertical displacement on the slip response.
Consistent lumped‐parameter models for unbounded soil: Physical representation
Authors: Wolf John P.
Published: April 2007

A systematic procedure to develop a consistent lumped‐parameter model with real frequency‐independent coefficients to represent the unbounded soil is developed. Each (modelled) dynamic‐stiffness coefficient in the frequency domain is approximated as a ratio of two polynomials, which is then formulated as a partial‐fraction expansion. Each of these terms is represented by a discrete model, which is the building block of the lumped‐parameter model. A second‐order term, for example, leads to a discrete model with springs and dampers with two internal degrees of freedom, corresponding to two first‐order differential equations, or, alternatively, results in a discrete model with springs, dampers and a mass with one internal degree of freedom, corresponding to one second‐order differential equation.

The lumped‐parameter model can easily be incorporated in a general‐purpose structural dynamics program working in the time domain, whereby the structure can even be non‐linear. A thorough evaluation shows that highly accurate results are achieved, even for dynamic systems with a cutoff frequency.
Dynamic pile‐soil‐pile interaction. Part I: Analysis of axial vibration
Authors: Gazetas George , Makris Nicos
Published: April 2007

Simple methods of analysis are developed for computing the dynamic steady‐state axial response of floating pile groups embedded in homogeneous and non‐homogeneous soil deposits. Physically‐motivated approximations are introduced to account for the interaction between two individual piles. It is found that such an interaction arises chiefly from the ‘interference’ of wave fields originating along each pile shaft and spreading outward. For homogeneous deposits the wave fronts originating at an individual pile are cylindrical and the interaction is essentially independent of pile flexibility and slenderness. For non‐homogeneous deposits the wave fronts are non‐cylindrical and ray‐theory approximations are invoked to derive pile flexibility‐dependent interaction functions.

Results are presented for the dynamic stiffness and damping of several pile groups, as well as for distribution of the applied load among individual piles. For deposits with modulus proportional to depth, the agreement with the few rigorous solutions available is encouraging. A comprehensive parameter study focuses on the effects of soil inhomogeneity and pile‐group configuration. It is demonstrated that the ‘dynamic group efficiency’ may far exceed unity at certain frequencies. Increasing soil inhomogeneity tends to reduce the respective resonant peaks and lead to smoother interaction functions, in qualitative agreement with field evidence.
Limitations on linear multistep methods for structural dynamics
Authors: Hulbert Gregory M.
Published: April 2007

When solving the equations of structural dynamics using direct time integration methods, algorithmic damping is useful to control spurious high‐frequency oscillations. Ideally, an algorithm should possess asymptotic annihilation of the high‐frequency response, i.e. spurious oscillations are eliminated after one time step. Numerous one‐step algorithms, spectrally equivalent to linear multistep (LMS) methods, have been developed which include controlled numerical dissipation. This paper proves that the only unconditionally stable, second‐order accurate, 3‐step LMS method possessing asymptotic annihilation is Houbolt's method, which is known to be overly dissipative in the low‐frequency regime. Thus, using LMS methods, obtaining asymptotic annihilation with little low‐frequency dissipation requires at least a 4‐step method.
Explanation for the numerous upper floor collapses during the 1985 Mexico city earthquake
Authors: Verde Roberto Villa
Published: April 2007

Presented herein are the results of a study carried out to investigate the prevalent factors that contributed to the collapse of the upper floors of a large number of buildings during the earthquake of September 19, 1985, in Mexico City. The study involves the review of the available data from such collapses, the identification of common characteristics among the buildings that suffered such type of collapse, the design of a typical 10‐storey reinforced concrete frame structure according to the 1976 Mexico City building code, and the non‐linear analysis of one of its frames under one of the accelerograms from the earthquake. It is found that in many cases the upper floor collapses might have occurred because the large accelerations and long duration of the earthquake induced in the failed buildings the formation of plastic hinges at their upper columns, and because these plastic hinges in turn induced the lateral instability of the affected storeys and the ones above them. It is also found that in some structures this failure mechanism can occur after plastic hinges are formed in most of their beams, and that it may result from the consequent elongation of their natural periods, their response in a second or third mode and in resonance with the ground motion that excites them, and their vibration in a mode not considered to be the predominant one in their design.
Seismic fracture analysis of concrete gravity dams
Authors: Pekau O. A. , Chuhan Zhang , Lingmin Feng
Published: April 2007

A numerical procedure for evaluation of the fracture process of gravity dams during strong earthquakes is presented. The BEM is used to discretize the dam reservoir system including the crack surfaces, and stress intensity factors at the crack tip are employed in a stage by stage procedure which simulates the crack extension. For each stage of constant crack length the mode superposition technique is applied; this is made possible by simulating the impact process of crack closing by a load pulse applied at the contact points which permits the structural stiffness to be assumed unchanged. To verify the proposed procedure, a cantilever beam model structure made of gypsum was tested on a shaking table. Good correlation with the numerical results was obtained, from which it is concluded that the procedure can be employed for evaluation of the crack propagation process in concrete structures subjected to dynamic loadings.
Vibrations of timoshenko beam‐columns on two‐parameter elastic foundations
Authors: Yokoyama T.
Published: April 2007

A finite element procedure is developed for analysing the flexural vibrations of a uniform Timoshenko beam‐column on a two‐parameter elastic foundation. The beam‐column is discretized into a number of simple elements with four degrees of freedom each. The governing matrix equation for small‐amplitude, free vibrations of the beam‐column on the elastic foundation is derived from Hamilton's principle. Several numerical examples are provided to show the effects of axial force, foundation stiffness parameters, partial elastic foundation, shear deformation and rotatory inertia on the natural frequencies of the beam‐column.
Comparison of seismic force reduction factors used in U.S.A. and Japan
Authors: Uang Chia‐Ming
Published: April 2007

This paper compares the seismic force reduction factors used in the United States and Japan. Since these factors appear in a very different format in the two countries, for comparison purposes, a general expression relating the force reduction factor to the structural ductility and overstrength factors is first established. This study shows that (i) the seismic design limit state philosophy applied to moderate and severe earthquakes is treated differently in each country; (ii) the Japanese code requires the designer to check explicitly the serviceability limit state, while the American codes do not require the member's strength be checked for the serviceability limit state; (iii) the force reduction factors used in Japan for the ultimate limit state check are significantly smaller than those used in the United States, and (iv) the force reduction factors used in Japan are even smaller if structural overstrength is not explicitly checked by designers.
Concentrically braced steel frames under seismic actions: Non‐linear behaviour and design coefficients
Authors: Perotti Federico , Scarlassara G. Paolo
Published: April 2007

The paper deals with the non‐linear dynamic analysis of concentrically braced pinned frames under earthquake conditions. A model is first presented for the behaviour of bars subjected to cyclic axial force, which takes into account the overall and local buckling phenomena, section shape, residual stresses, material behaviour and damage accumulation due to low‐cycle fatigue and fracture. Dynamic analyses of bracing systems are then described: these have been performed, on the basis of the axially loaded bar model, within the framework of a simplified procedure for the determination of optimal design factors. The results obtained are first reported for the case of one‐storey systems; an example of the behaviour of a four‐storey system is given finally.
Seismic response of tied‐back retaining walls
Authors: Siller Thomas J. , Christiano Paul P. , Bielak Jacobo
Published: April 2007

Parametric studies based on finite element simulations were conducted to establish the fundamental mechanisms by which tied‐back walls respond to travelling displacement pulses. Considering first linear elastic soil behaviour, we observed that the flexural stiffness of the wall hardly affects maximum transient displacements. Rather, the transient response is determined mainly by the ratio of pulse wavelength to wall height. The maximum load carried by the anchor was found to increase with increasing anchor stiffness. For short wavelengths, on the order of less than two times the wall height, the maximum displacements and displaced shapes are affected significantly by the inclination of the anchor. The importance of the anchor stiffness suggested by the linear elastic analysis was confirmed by the non‐linear analysis. A stiff anchor suppressed permanent displacements in the vicinity of the anchor, but did not substantially reduce permanent displacements elsewhere. As peak accelerations increased from 0.1 g to 0.4 g, permanent wall displacements increased significantly.
Seismic behaviour of pile groups by hybrid experiments
Authors: Toki Kenzo , Sato Tadanobu , Kiyono Junji , Garmroudi Nozar Kishi , Emi Susumu , Yoshikawa Masaaki
Published: April 2007

Non‐linear seismic soil‐pile interaction was studied with a hybrid procedure that used a pseudo‐dynamic testing (PDT) method modified to account for frequency dependence and developed for foundation‐soil systems. The numerical scheme used in the conventional PDT was improved by the introduction of a time‐dependent pseudo‐forcing function derived from the frequency‐dependent dynamic characteristics of the system by Hilbert transformation in the frequency domain. Single, 2‐, 3‐ and 9‐pile group foundation models were used, their mechanical characteristics later being determined from static and forced vibration dynamic tests. Amplitude scaling was used for three recorded accelerograms. Data recorded during an earthquake at the site of the experiments revealed that the proposed methodology predicts well seismic nonlinear interaction and accounts for frequency dependence and non‐linearity in the time domain.
A lagrange multiplier solution method for pounding of buildings during earthquakes
Authors: Papadrakakis M. , Mouzakis H. , Plevris N. , Bitzarakis S.
Published: April 2007

An effective solution method for studying the pounding response of two or more adjacent buildings during earthquakes is presented. The method is based on the Lagrange multiplier approach by which the geometric compatibility conditions due to contact are enforced. The energy and momentum balance criteria for the contacting bodies are satisfied according to the laws of impact with proper post‐impact conditions, which can also take into account local energy absorption phenomena during impact. A solution scheme is proposed which can be incorporated easily into existing computer programs for static and dynamic analysis of structures. The applicability of the algorithm is illustrated in a number of selected sample problems and the correlation of numerical results to analytical solutions, whenever possible, is very satisfactory.
Seismic response of unbraced steel frames
Authors: Sivakumaran K. S.
Published: April 2007

In the analysis and design of unbraced steel frames various models are employed to represent the behaviour of beam‐to‐column connections. In one such model, termed here as ‘Simple Construction’, pinned connections are assumed when resisting gravity loads, whereas the same connections are assumed to be moment‐resistant rigid connections when resisting lateral loads due to an earthquake or wind. Such connections are designed for moments due to lateral loads only; thus, they are not only flexible but may yield when the gravity and lateral loads act concurrently. This paper establishes the seismic performance of two (one 5‐storey and the other 10‐storey) unbraced steel building frames designed based on the ‘Simple Construction’ technique and on limit state principles. The first part of the paper describes briefly the design of such frames and compares their static responses with the corresponding responses of frames designed based on the ‘Continuous Construction’ assumption. Using realistic moment‐rotation behaviour for flexible beam‐to‐column connections and realistic member behaviour, the non‐linear dynamic responses of such frames for the 1940 El Centro record and 2 times the 1952 Taft record have been established using step‐by‐step time‐history analyses. Floor lateral displacement envelopes, storey shear envelopes and cumulative inelastic rotations of beams, columns and connections are presented. The results indicate that the ‘Simple Construction’ frames experience larger lateral deflections while attracting lesser storey shears. During a major earthquake, the columns and connections of the ‘Simple Construction’ frames experience yielding, whereas in ‘Continuous Construction’ frames the beams and columns experience yielding. The cyclic plastic rotations in the connections and in the columns associated with ‘Simple Construction’ frames are found to be considerably higher.
Evaluation of the earthquake performance of anchored wine tanks during the San Juan, Argentina, 1977 earthquakexs
Authors: Manos George C.
Published: April 2007

This paper details the damage sustained by a number of wine tanks during the San Juan, Argentina, 1977 earthquake. The available ground motion information is used to compare the actual tank performance with that predicted. Two of the tanks examined were located quite near the two accelerographs that recorded the ground motion in the city of San Juan for the main shock. An empirical attenuation formula which describes the intensity of the shaking was derived for this earthquake and used in a quantitative evaluation of the performance of a number of other tanks. By correlating and comparing the observed performance of the anchors and what was predicted we see the predictions are upheld by the actual damage. When the anchoring system failed during the earthquake the tanks were rendered effectively unanchored. Consequently, the state of stress that results from their base uplift was then examined in conjunction with the tank wall stability approach proposed by the author, and seen to give results consistent with the observed tank wall performance.
Equivalent ductility factors, taking into account low‐cycle fatigue
Authors: Fajfar Peter
Published: April 2007

During strong earthquakes, the deformation capacity of structures is reduced due to the cumulative damage caused by cyclic load reversals. In the paper, equivalent (reduced) ductility factors have been proposed, which take into account this effect. They are based on different failure hypotheses. Ductility reduction due to low‐cycle fatigue is controlled by a dimensionless parameter γ, which is a function of dissipated hysteretic energy, maximum displacement and the natural frequency of the structural system, and which has been proved to be a relatively stable quantity in the whole period range. If approximate values for γ are used, the determination of equivalent ductility is very simple, and thus appropriate for design purposes. The formulae for equivalent ductility factors include damage indices, and permit the designer to choose acceptable level of structural damage explicitly. As an example, equivalent ductility factors have been used to construct inelastic acceleration spectra, which are proportional to strength demand, for the El Centro 1940 SOOE record. The results have been compared with the ‘exact’ spectra obtained by non‐linear dynamic analysis.
Seismic analysis of the fatih sultan mehmet (second Bosporus) suspension bridge
Authors: Dumanoglu A. A. , Brownjohn J. M. W. , Severn R. T.
Published: April 2007

Theoretical dynamic characteristics of the Fatih Bridge in terms of natural frequencies and mode shapes of free vibration were obtained using a range of finite element models. Based on this free‐vibration data, separate analyses of the asynchronous response of the bridge to earthquake excitation in three orthogonal axes with different speeds of wave propagation, and of stochastic response to vertical excitation were used to estimate levels of dynamic response due to seismic loading.

Fatih is the third of three modern European long‐span box‐girder suspension bridges that have been investigated and the relationship of the different design features and the dynamic responses of this type of bridge is reviewed.

The main conclusion is that where seismic response is an important consideration, the effects of asynchronous excitation can be significant and must be considered.
Some aspects of testing small‐scale masonry building models on simple earthquake simulators
Authors: Tomaževič Miha , Velechovsky Tomaž
Published: April 2007

The basic aspects of testing small‐scale masonry building models on simple earthquake simulators are discussed. Since the scale effects represent a difficult problem to solve, the overall seismic behaviour of structural systems, and not the behaviour of structulal details, has been studied by testing the reduced‐sized models on a simple earthquake simulator. Accurate results regarding the dynamic behaviour and failure mechanism of the tested structures have been obtained by means of testing the relatively simple, adequately designed small‐scale masonry building models. A simple earthquake simulator capable of simulating the uni‐directional earthquake ground motion has been developed to study the seismic behaviour of masonry building models. Although a multipurpose programmable actuator was used to drive the shaking table, the comparison of the dynamic characteristics of the generated shaking‐table motion and the earthquake acceleration records used for the simulation of seismic loads showed an acceptable degree of correlation between the input and output seismic motion.
Assessment of the Application of Fuel Cell APUs and Starter‐Generators to Reduce Automobile Fuel Consumption
Authors: Grube T. , Höhlein B. , Menzer R.
Published: March 2007

Auxiliary power units (APUs) provide electrical power, with favourable efficiency and independent of the drive system, for a variety of mobile applications. The demand for electricity increases with increasing demand for convenience and safety functions, as well as for control and regulation services. Examples of these functions are engine‐independent air conditioning in motor vehicles or by‐wire technologies in aircraft. The additional power must be provided with the greatest possible efficiency, due to the general requirement for an overall reduction in fuel consumption.

This contribution compares the present status of on‐board electricity supply in conventional passenger cars with variants, based on the starter‐generator and the auxiliary power unit (APU). The results of a process engineering analysis define the potential efficiency of electricity generation with solid oxide fuel cell (SOFC) based systems. In addition to the load profiles of the auxiliaries, the driving cycle must be defined within the framework of a model‐based dynamic drive train simulation, in order to finally determine the fuel consumption per kilometre in dynamic operation. As a result, the fuel consumption of the variants investigated is presented and the possibilities for applying fuel cell APUs and starter‐generators assessed.
N‐WASP regulates extension of filopodia and processes by oligodendrocyte progenitors, oligodendrocytes, and Schwann cells—implications for axon ensheathment at myelination
Authors: Bacon Claire , Lakics Viktor , Machesky Laura , Rumsby Martin
Published: April 2007

The molecular mechanisms used by oligodendrocyte precursor cells (OPCs), oligodendrocytes (OLs), and Schwann cells (SCs) to advance processes for motility in the developing nervous system and to ensheath axons at myelination are currently not well defined. Here we demonstrate that OPCs, OLs, and SCs express the major proteins involved in actin polymerization‐driven protrusion; these key proteins including F‐actin, the Arp2/3 complex, neural‐Wiskott Aldrich Syndrome protein (N‐WASP) and WAVE proteins, and the RhoGTPases Rac and Cdc42 are present at the leading edges of processes being extended by OPCs, OLs, and SCs. We reveal by real‐time PCR that OLs and SCs have different dominant WAVE isoforms. Inhibition of the WASP/WAVE protein, N‐WASP, with wiskostatin that prevents activation of the Arp2/3 complex, blocks process extension by OPCs and SCs. Inhibition of N‐WASP also causes OPC and SC process retraction, which is preceded by retraction of filopodia. This implicates filopodia in OPC and SC process stability and also of N‐WASP in OPC and SC process dynamics. We also demonstrate that p34 (a component of the Arp2/3 complex), WASP/WAVE proteins, actin, α‐tubulin, Rac, Cdc42, vinculin, and focal adhesion kinase are detected in water‐shocked myelin purified from brain. Inhibition of N‐WASP with wiskostatin decreases the number of axons undergoing initial ensheathment in intact optic nerve samples and reduces the Po content of dorsal root ganglia:SC co‐cultures. Our findings indicate that OPCs, OLs, and SCs extend processes using actin polymerization‐driven protrusion dependent on N‐WASP. We hypothesize that inner mesaxons of OLs and SCs use the same mechanism to ensheath axons at myelination. © 2007 Wiley‐Liss, Inc.
Serotonin reuptake inhibitors in pregnancy and the risk of major malformations: a systematic review
Authors: Bellantuono Cesario , Migliarese Giovanni , Gentile Salvatore
Published: April 2007

Objective

To review studies conducted to establish the risk of major congenital malformations in women exposed to serotonin reuptake inhibitors (SRIs) during the first trimester of pregnancy.

Methods

A literature research was conducted within PsychoINFO, EMBASE, MEDLINE and Cochrane databases from 1966 to October 2006, to identify studies assessing the risk of major malformations in infants whose mother was taking SRIs (SSRIs and SNRIs) during the first trimester of pregnancy.

Results

Fifteen studies were selected for the analysis: seven adopted a prospective cohort design and seven a retrospective design, of these one was a case‐control study.

Data Synthesis and Conclusions

The reviewed studies suggest that exposure to fluoxetine, sertraline, citalopram and venlafaxine in early pregnancy is not associated with an increased risk of major congenital malformations. For paroxetine, recent data call for caution in prescribing such a drug in early pregnancy. For the other SRIs, the risk remains substantially undetermined, as data are so far scanty. Given this background, large prospective cohort studies are urgently needed to better assess the risk/benefit ratio of SRIs‐treatment during pregnancy. Copyright © 2007 John Wiley & Sons, Ltd.
Environmental influences on reading‐related outcomes: an adoption study
Authors: Petrill Stephen A. , Deater‐Deckard Kirby , Schatschneider Christopher , Davis Chayna
Published: April 2007

Evidence from intervention studies, quantitative genetic and molecular genetic studies suggests that genetic, and to a lesser extent, shared environmental influences are important to the development of reading and related cognitive skills. The Northeast‐Northwest Collaborative Adoption Projects (N2CAP) is a sample of 241 adoptive families, containing 354 children and their adoptive parents. Negative parent outcome × child age interactions significantly predicted child outcomes, suggesting that shared environmental influences related to parent–offspring resemblance, although modest, are most salient in younger children. Additional analyses suggested that identified measures of the family environment largely accounted for these parent–offspring correlations. Copyright © 2007 John Wiley & Sons, Ltd.
Finding a safe place to cross the road: the effect of distractors and the role of attention in children's identification of safe and dangerous road‐crossing sites
Authors: Tabibi Z. , Pfeffer K.
Published: April 2007

Negotiating traffic requires the ability to focus attention on the traffic environment and ignore distracting stimuli. The aims of this study were (1) to examine the effect of distractors on children's ability to identify safe and dangerous road‐crossing sites and (2) to examine the relationship between identification of safe/dangerous sites and attention (selective attention, attention switching, sustained attention and divided attention). Participants were 88 children (aged between 6 and 11 years) and 29 adults. Ability to identify safe and dangerous road‐crossing sites was assessed using computer presentations of sites with and without visual and auditory distractions. Measures of attention were examined using the Test of Everyday Attention (child and adult versions). The ability to identify safe and dangerous road‐crossing sites and performance on the attention tests were found to improve with increasing age. Correct identification of safe/dangerous road‐crossing sites was related to selective attention and divided attention for children but not for adults. Road safety training should take into account the development of these skills. Copyright © 2007 John Wiley & Sons, Ltd.
Stability and prediction of parenting stress
Authors: Östberg Monica , Hagekull Berit , Hagelin Elisabet
Published: April 2007

The study focused on stability and prediction of parenting stress experiences over a 6‐year period. Mothers (N=93) who had received a clinical intervention for feeding or sleeping problems during infancy (Time 1; T 1) were followed‐up when the children were 5–10 years old (Time 2; T 2). An age‐ and sex‐of‐child matched normal group was used for comparison of stress levels at T 2. Parenting stress was measured by the Swedish Parenthood Stress Questionnaire, which consists of a general parenting stress scale and sub‐scales tapping different aspects of parenting stress experiences. T 1 predictors were clinical assessments of child problem load, maternal unresponsiveness, and family psychosocial problems. T 2 predictors were mother‐reported concurrent child problem load and psychosocial problems. The individual stability in stress experiences was moderate. Effect sizes indicated that mothers with early clinical contacts had reduced their stress to levels close to those in the normal sample. Parenting stress at T 2 could be predicted from early and from concurrent child and family problems. The results point to the relevance of early clinical assessments and to the importance of a sub‐area approach in parenting stress research, as there were differences between stress sub‐areas regarding both prediction and stability. Copyright © 2007 John Wiley & Sons, Ltd.
Frequent inactivation of SPARC by promoter hypermethylation in colon cancers
Authors: Yang Eungi , Kang Hyun Ju , Koh Kwi Hye , Rhee Hwanseok , Kim Nam Kyu , Kim Hoguen
Published: March 2007

Epigenetic modification of gene expression plays an important role in the development of human cancers. The inactivation of SPARC through CpG island methylation was studied in colon cancers using oligonucleotide microarray analysis and methylation specific PCR (MSP). Gene expression of 7 colon cancer cell lines was evaluated before and after treatment with the demethylating agent 5‐aza‐2′‐deoxycytidine (5Aza‐dC) by oligonucleotide microarray analysis. Expression of SPARC was further examined in colon cancer cell lines and primary colorectal cancers, and the methylation status of the SPARC promoter was determined by MSP. SPARC expression was undetectable in 5 of 7 (71%) colorectal cancer cell lines. Induction of SPARC was demonstrated after treatment with the demethylating agent 5Aza‐dC in 5 of the 7 cell lines. We examined the methylation status of the CpG island of SPARC in 7 colon cancer cell lines and in 20 test set of colon cancer tissues. MSP demonstrated hypermethylation of the CpG island of SPARC in 6 of 7 cell lines and in all 20 primary colon cancers, when compared with only 3 of 20 normal colon mucosa. Immunohistochemical analysis showed that SPARC expression was downregulated or absent in 17 of 20 colon cancers. A survival analysis of 292 validation set of colorectal carcinoma patients revealed a poorer prognosis for patients lacking SPARC expression than for patients with normal SPARC expression (56.79% vs. 75.83% 5‐year survival rate, p = 0.0014). The results indicate that epigenetic gene silencing of SPARC is frequent in colon cancers, and that inactivation of SPARC is related to rapid progression of colon cancers. © 2007 Wiley‐Liss, Inc.