bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simplified analysis of unanchored tanks
Authors: Peek R. , Jennings P. C. 
Published: April 2007

AbstractLocal uplift of the tank wall is perhaps the most important characteristic of the seismic behaviour of unanchored liquid storage tanks made out of steel. Such uplift is necessary, because unanchored tanks rely primarily on the weight of the liquid resting on an uplifted portion of the base plate to balance the overturning moments that occur during strong shaking. A simplified method of analysis for static lateral loads is developed, based on the assumption that the restraining action of the base plate can be modelled with equivalent, non‐linear springs. This assumption, together with a Fourier decomposition of the displacements, simplifies the problem to the extent that it can be solved on a personal computer. The solutions are compared with those from experiments and those from current U.S. design analysis methods.
Analysis of unanchored liquid storage tanks under lateral loads
Authors: Peek Ralf 
Published: April 2007

AbstractMany liquid storage tanks consist of a steel cylindrical shell, which is welded to a base plate, but not fixed to the foundation. When such an unanchored tank is subjected to lateral loads due to earthquake induced hydrodynamic pressures in the liquid, the tank wall tends to uplift locally, pulling the base plate up with it. The contact problem of the partially uplifted base plate and its interaction with the the cylindrical shell is solved in this paper using the finite difference energy method, and a Fourier decomposition of the displacements in the circumferential direction. Non‐linearities due to contact, finite displacements and yield of the steel are included in the analysis. However, the equations for the shell are linearized. This uncouples the equations for the Fourier displacement coefficients in the cylindrical shell, and enables the degrees of freedom for the shell to be eliminated by static condensation at very little computational cost.Comparing the analytical results to (for the most part existing) experimental results, produces good agreement in some cases and not so good in others. A number of effects that could give rise to such differences are discussed. In most cases they represent experimental conditions that are not known or modelled in the analysis. The analysis results are also compared to those from a simplified analysis in which the hold‐down action of the base plate is modelled by means of nonlinear Winkler springs.
Buckling and vibration analysis of flexible beams resting on an elastic half‐space
Authors: Karamanlidis Dimitrios , Prakash Vikas 
Published: April 2007

AbstractThe present paper deals with the buckling and vibration of prismatic beams resting on an elastic half‐space. The computational procedure developed herein utilizes the advantages of both an analytical approach and a finite element scheme. This is accomplished by deriving exact frequency and axial force dependent stiffness matrices using the analytical solutions of the governing differential equation as ‘shape functions’. The major advantages of the proposed approach over previous ones are pointed out and discussed in detail. Numerical results demonstrating the performance of the proposed method are presented in the final part of the paper.
A plane strain soil‐structure interaction model
Authors: Dangla P. 
Published: April 2007

AbstractA plane strain model for dynamic soil‐structure interaction problems under harmonic state is presented. The boundary element method is used to study the response of a homogeneous isotropic linear elastic soil. The far field displacement at the free surface is approximated by an outgoing Rayleigh wave. The finite element method is used to describe the response of the building, of the foundation and possibly of a finite part of the inhomogeneous non‐linear soil. Two coupling procedures are described. The model is applied to a problem previously studied in the antiplane case. Incident P, SV and Rayleigh waves are considered. The results show an amplification and an attenuation of the structure motion with frequency when incident Rayleigh waves and P, SV body waves are respectively considered.
Boundary element reservoir model for seismic analysis of gravity dams
Authors: Humar J. L. , Jablonski A. M. 
Published: April 2007

AbstractThe boundary element method has been successfully applied in the past to the analysis of hydrodynamic forces in two‐ and three‐dimensional finite water reservoirs subjected to seismic ground motions. In extending the method to an infinite reservoir, the loss of energy due to pressure waves moving away towards infinity must be taken into account. In addition, for both finite and infinite reservoirs, energy is lost owing to partial absorption of the waves incident on a flexible bottom consisting of alluvial deposits. This paper presents the results of more recent research on the application of the boundary element method to the analysis of 2D reservoir vibration. Two different formulations are used: a constant boundary element formulation and a linear boundary element formulation. Special boundary conditions to treat infinite radiation and foundation damping have been incorporated in both formulations. Numerical results have been obtained for each of the two alternative formulations and compared against each other as well as with classical solutions and results obtained by other researchers.
Stiffness identification of two‐ and three‐dimensional frames
Authors: Torkamani Morteza A. M. , Ahmadi Ahmad K. 
Published: April 2007

AbstractFour widely used structural system identification methods are presented. Based on Bayesian estimation theory, two new formulae and their derivations are shown. Time domain responses of two frames when subjected to the ground motion of the El Centro earthquake are computed then transformed to the frequency domain. Frequencies and mode shapes of frames are extracted from Fourier spectra. Using these frequencies and mode shapes, a parametric study is conducted, and the system identification methods are compared and discussed. The importance of a prior analytical model on the rate of convergence of the revised parameters is investigated. Recommendations are given regarding the feasibility of each method for more accurate estimation. A model suitable for parameter identification of three‐dimensional frames is presented. This model, with different identification methods, is used to estimate the parameters of a two‐storey frame.
Stiffness identification of a tall building during construction period using ambient tests
Authors: Torkamani Morteza A. M. , Ahmadi Ahmad K. 
Published: April 2007

AbstractAmbient response measurements were made on an eighteen‐storey building at three different stages of construction to detect any changes in the frequencies, mode shapes and stiffness with construction. The first nine frequencies and corresponding mode shapes for each stage of construction are found. A comparison is made among these mode shapes and frequencies and with the mode shapes and frequencies of an analytical model incorporating beams, columns, shear walls, panels and diagonal elements. The added effects, on frequencies and mode shapes, of non‐structural elements such as stairs, elevators, claddings and partition walls are studied. Using Improved Statistical Structural Identification, an attempt is made to study the stiffening effect of non‐structural elements by updating the stiffness matrix of the building.
A note on non‐stationary stochastic response and strong motion duration
Authors: Zembaty Zbigniew 
Published: April 2007

AbstractAn analysis of the influence of strong motion duration on the response spectra is presented. The analysis is based on the concept of evolutionary power spectral density and first passage estimations for non‐stationary random vibrations. To compare the response for different durations the criteria of constant Arias intensity and constant excitation level have been applied. The paper presents a numerical analysis of the effect of strong motion duration on various response statistics for a linear oscillator. Results indicate a decrease of peak response and first passage probability with increasing strong motion duration for constant Arias intensity.
The effect of earthquake duration on the damage of structures
Authors: Jeong Garrett D. , Iwan Wilfred D. 
Published: April 2007

AbstractThis paper presents a theoretical analysis of the effect of duration on the damage of structures subjected to earthquakes. The earthquake excitation is modelled by a non‐stationary random process whose response spectrum is probabilistically consistent with a design response spectrum specified independently of the duration. Damage is assumed to accumulate with the cyclic application of large strains in the structural members. Two types of structure are examined: one representative of a steel structure and the other reprsentative of a reinforced concrete structure. The level of expected damage is found to be a strong function of both the ductility of the response and the duration of the excitation. Results are presented for systems with linear stiffness and a particular form of softening behaviour.
Optimum strong‐motion array geometry for source inversion
Authors: Iida Masahiro , Miyatake Takashi , Shimazaki Kunihiko 
Published: April 2007

AbstractOptimum strong‐motion array geometry for source inversion is quantitatively determined for each of three types of earthquake faults: strike—slip, dip‐slip and offshore subduction thrust. The estimation is done by using the source inversion method1,2 previously developed and based on Wolberg's prediction analysis.3 Only the far‐field S waves are taken into account in source inversion; we test only the ability to estimate seismic moments of subfault elements. A comparison of the optimum array geometries obtained in this study with the ones proposed on the basis of an empirical judgment at the 1978 International Workshop on Strong‐Motion Earthquake Instrument Arrays4 shows that the Workshop geometries are not the best ones as far as source studies are concerned. The most preferable array involves two different kinds of stations regardless of the target fault type: stations close to the fault and aligned parallel to its strike, and stations surrounding the fault area with good azimuthal coverage. The former stations resolve the later stage of the rupturing process while the latter stations resolve the earlier stage.
Vibration suppression of structures
Authors: Ebrahimi N. D. 
Published: April 2007

AbstractA procedure for vibration suppression of elastic structures and systems is introduced in this paper. First, the equations of the response of the system to external forces, based on a discretized linear model, are developed. Next, the vibration suppression is formulated as a minimization problem with control (external) forces as unknowns. Then, the optimality condition is applied to this problem and a set of linear simultaneous equations is obtained for the unknown forces. The scheme is applied to a number of simple examples for illustration. The results show that the procedure is very effective and, at the same time, very flexible compared to methods that are based on continuous models (partial differential equations). The actual (hardware) implementation can be achieved by means of either passive absorbers or active forces (actuators).
A comparative study of performances of various base isolation systems, part I: Shear beam structures
Authors: Su Lin , Ahmadi Goodarz , Tadjbakhsh Iradj G. 
Published: April 2007

AbstractA comparative study of performances of different base isolators for shear beam type structures is carried out. Several leading base isolation systems, including the laminated rubber bearing with and without lead plug, the resilient‐friction base isolator with and without sliding upper plate, and the EDF system are considered. Displacement and acceleration response spectra for a shear beam structure subject to the accelerograms of the N00W component of El Centro 1940 and the N90W component of Mexico City 1985 earthquakes and their magnified forms are evaluated. A series of parametric studies is carried out and advantages and disadvantages of various base isolation systems are identified. Comparisons of the results with the response spectra of a fixed‐base structure show that the base isolation systems are, in general, highly effective in reducing the peak acceleration transmitted to the superstructure. Thus, the deflections and stresses generated in a base‐isolated structure are significantly lower than those of a fixed‐base one. Furthermore, the results of the study also show that the friction‐type base isolators are less sensitive to severe variations in frequency content and amplitude of the ground acceleration.
Correlation studies using the equivalent base horizontal acceleration method
Authors: Uang Chia‐Ming , Bertero Vitelmo V. , Clough Ray W. 
Published: April 2007

AbstractThe equivalent base horizontal acceleration concept was developed for calculating the response of test structures to shaking table excitations, to account for pitching interaction effects of the table. Using the procedure, analysis‐experiment comparisons were made of the shaking table tests of a 0–3‐scale model of a six‐storey concentrically K‐braced steel structure. The correlation of the analytical and experimental results was excellent in both the elastic and inelastic ranges of structural response.
Response of base‐isolated buildings to random excitations described by the Clough‐Penzien spectral model
Authors: Lin B. C. , Tadjbakhsh I. G. , Papageorgiou A. S. , Ahmadi G. 
Published: April 2007

AbstractThe stationary response of base‐isolated buildings subjected to earthquake excitation is studied. The frequency content of earthquake input is described by the Clough‐Penzien spectral model. The response parameters of interest are (1) the root‐mean‐square (RMS) displacement σx of the basement relative to the foundation (i.e. shear deformation of the isolation system) and (2) the ratio (σa/σa0) of the RMS value of the absolute acceleration at the roof of the isolated structure over the corresponding value when the isolation system is locked. The variation of these response parameters with the effective frequency f0 of the base‐isolated structure is investigated. As input, earthquakes with moment magnitudes M = 7‐3 and M = 6‐0 are considered. The acceleration spectra corresponding to these two earthquake sizes have pronouncedly different frequency content over the frequency range 0–1‐1–0 Hz which is of primary importance for base‐isolated structures. An important conclusion that comes from these analyses is that confidence in the effectiveness of a base‐isolated system should be based primarily on its capacity to absorb/dissipate energy and less on its influence in shifting the fundamental period of the structure out of the range of dominant earthquake energy.
Simplified analysis method for multistorey base‐isolated structures on viscoelastic halfspace
Authors: Siddiqui Faruq M. A. , Constantinou M. C. 
Published: April 2007

AbstractA simplified procedure for the analysis of single‐storey base‐isolated structures on a viscoelastic halfspace is extended to multistorey structures. Results of displacements and base shear obtained by this procedure compare favourably to exact results obtained by a computer program that has been developed.
Seismic amplification—Mexico City
Authors: Abbiss C. P. 
Published: April 2007

AbstractThe large amplification experienced at Mexico City during the earthquake of September 1985 is shown to be due to a standing shear wave set up in the clay layer. The frequency and amplitude of this wave were controlled by the properties of the clay which led directly to such high accelerations. The response curve due to the clay layer is calculated from field and laboratory measurements of the properties of the clay. There is good agreement with that obtained from field observations of ground motion.
Steady state rocking response of rigid blocks part 1: Analysis
Authors: Tso W. K. , Wong C. M. 
Published: April 2007

AbstractThe result of a theoretical study on the rocking response of rigid blocks subjected to sinusoidal base motion is presented. The study indicates that, for a given excitation amplitude and frequency, a rigid block can respond in several different ways. Based on analysis, the regions of different classes of steady state symmetric response solutions are mapped on the excitation amplitude‐frequency parameter space. The steady state response solutions (both harmonic and subharmonic) are classified into two classes, out‐of‐phase and in‐phase with respect to the excitation. Only out‐of‐phase solutions are found to be stable. A parametric study shows that steady rocking response amplitude is highly sensitive to the size of the block and the excitation frequency in the low frequency range. It is relatively insensitive to the excitation amplitude and the system's coefficient of restitution of impact. For two blocks of the same aspect ratio and coefficient of restitution subjected to the same excitation, the larger block always responds in smaller amplitude than the smaller block. Computer simulation is carried out to study the stability of the symmetric steady state response solutions obtained from analysis. It is found that as the excitation frequency is decreased beyond the boundary of stable symmetric response, the response becomes unsymmetric where the mean amplitude of oscillation is non‐zero. Further decrease in excitation frequency beyond the stable unsymmetric response boundary causes instability in the form of overturning.
Steady state rocking response of rigid blocks part 2: Experiment
Authors: Wong C. M. , Tso W. K. 
Published: April 2007

AbstractThe results of an experimental investigation on the rocking response of rigid blocks subjected to sinusoidal base motion is presented. It is shown that two common types of steady state response are harmonic and 1/3 subharmonic response. The measured steady state response amplitudes correlate well with theoretical predictions for both harmonic and 1/3 subharmonic responses. Within each type of steady state response, theoretical studies show that the system may respond in either a symmetric or an unsymmetric mode. A symmetric mode denotes that the block oscillates about a mean zero position while an unsymmetric mode implies the mean position of oscillation is at an inclined position. One form of unsymmetric response was observed in the experiment. In addition, almost periodic responses were also observed in the experiment, although their existence has not been reported in theoretical studies.
An algorithm for the optimum design of braced and unbraced steel frames under earthquake loading
Authors: Gülay Gülten , Boduroǧlu Hasan 
Published: April 2007

AbstractA solution technique based on the sequential linear programming (SLP) method is presented for the optimum design of braced and unbraced steel frames in seismic regions. First, the optimum rigidity distribution of the frames under static loading is computed, then the optimization procedure is repeated under the combined loading, setting lower bounds on the optimum static cross‐sectional areas and increasing allowable stresses.The stiffness, stress, displacement and side constraints are included in the optimization problem. As a result, a highly non‐linear mathematical programming problem is produced. A non‐linear programming algorithm is offered for the solution which is based on the successive linearization of non‐linear expressions and employs the simplex routine in an iterative manner.Design variables are chosen to be the free nodal displacements and the cross‐sectional areas of the members, while the objective function is taken to be the minimization of the total volume of the structure.As numerical applications, optimum weights of several frames (unbraced, concentrically and eccentrically braced) under static and combined loading cases are computed and the results are compared with those available in the literature.
Ritz vectors and generation criteria for mode superposition analysis
Authors: Joo Kuan‐Jung , Wilson Edward L. , Leger Pierre 
Published: April 2007

AbstractA generation procedure of Ritz vectors to control the inclusion of static effect and the number of vectors in mode superposition dynamic analysis is presented. The original algorithm of the Ritz vectors15 is modified to improve stability in the generation procedure and to include the use of static residual. To reject unimportant Ritz vectors, cut‐off criteria, which are based on the participation of mass distribution and spatial load distribution, are proposed. Numerical examples are presented to illustrate the effectiveness of the derived Ritz vectors over the eigenvectors and the performance of the cutoff criteria in the mode superposition dynamic analysis.
Correlation of cylindrical tank wall buckling with an earthquake motion recorded at a small distance from the tank
Authors: Manos George C. , Shibata Heki , Shigeta Tatsuya 
Published: April 2007

AbstractThe bulging observed on the wall of a ground supported cylindrical storage tank, located at the Chiba Experimental Station of the University of Tokyo, is investigated. This damage is correlated with a ground motion recording obtained very near the tank base during a moderately strong earthquake that occurred on September 25, 1980 not far from the Chiba Experimental Station. From this correlation the importance of the horizontal excitation in amplitude and direction is clearly established. In addition, good agreement can be seen between the predicted tank wall earthquake performance, derived by an empirical approach proposed by the first author, and the shell deformation observed at the Chiba Experimental Station.
Interaction of an axisymmetric body with obliquely incident seismic waves by global local finite elements
Authors: Avanessian V. , Dong S. B. , Muki R. 
Published: April 2007

AbstractAsymmetric steady‐state structure‐media interaction due to obliquely incident body waves is investigated via a version of the global local finite element method. In the present version, a local region that houses an axisymmetric structure is modelled by conventional finite elements, while the behaviour in the remaining portion of the homogeneous semi‐infinite medium is presented by the spherical harmonics that are the eigensolutions of the entire space problem. The solution scheme involves (1) full displacement and traction continuity along the boundary between the local and the exterior regions and (2) satisfaction of the traction‐free requirement on the surface of the half‐space beyond the discretized region by virtue of a sequence of integral constraints of the non‐zero weighted surface tractions of the spherical harmonics. The numerical results presented are for a perfectly bonded rigid circular foundation resting on the surface of the half‐space and subjected to obliquely incident body waves. Dependence of the displacement response of the footing upon incident angles and dimensionless wave numbers is thoroughly studied.