bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural response to non‐stationary multiple‐support random excitation
Authors: Perotti Federico 
Published: April 2007

AbstractThe 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

AbstractSeismic 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

AbstractSteady 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

AbstractThe 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

AbstractAbdel‐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

AbstractThe 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

AbstractBaranov 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

AbstractIt 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

AbstractIn 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

AbstractA 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

AbstractSimple 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

AbstractWhen 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

AbstractPresented 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

AbstractA 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

AbstractA 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

AbstractThis 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

AbstractThe 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

AbstractParametric 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

AbstractNon‐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

AbstractAn 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

AbstractIn 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.