bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seismic response of torsionally coupled base isolated structures
Authors: Pan Tso‐Chien , Kelly James M. 
Published: March 2007

AbstractAn analytical study of the seismic response of typical base isolated structures mounted on rubber bearings is presented. Isolated buildings are liable to have closely spaced lower modes of vibration with small eccentricity between centres of mass and rigidity. The isolated structure is modelled as a rigid deck with lumped masses supported on axially inextensible elastomeric rubber bearings. This simplified system has three degrees of freedom (dof), two translations and one rotation in the horizontal plane.The Green's functions for the displacement response of the 3 dof system are derived for both undamped and damped cases with small and large eccentricities. The small eccentricity case is taken from a specific isolated building, while the large eccentricity case arises from the 5 per cent accidental eccentricity which is required by various seismic codes.An interaction equation for normalized displacements is established for an idealized flat velocity spectrum or hyperbolic acceleration spectrum. An isolated building on rubber bearings would have its fundamental period fall into this range of a design spectrum.Numerical results for the specific building subjected to the El Centro earthquake of 1940 are presented. Both the time history and the response spectrum modal superposition analysis were performed. In the response spectrum analysis, the Complete Quadratic Combination (CQC) showed superiority over the Square Root of the Sum of Squares (SRSS) in estimating maximum responses.It is concluded that the effect of torsional coupling on the transient response of base isolated structures is insignificant, due to the combined effect of the time lag between the maximum translational and torsional responses and the influence of damping in the isolation system which for elastomeric bearings can be as high as 8 to 10 per cent.
Effects of reservoir bottom absorption on earthquake response of concrete gravity dams
Authors: Fenves Gregory , Chopra Anil K. 
Published: March 2007

AbstractA procedure is presented to analyse the response of concrete gravity dams due to horizontal and vertical earthquake ground motion components considering dam‐water interaction and partial absorption of hydrodynamic pressure waves at the reservoir bottom into the foundation medium. The effects of reservoir bottom absorption on the hydrodynamic force on a rigid dam are examined first. The harmonic response of an idealized dam cross‐section is presented for a wide range of parameters characterizing the properties of the dam, the impounded water and the foundation medium. Based on these frequency response functions the effects of dam‐water interaction and of reservoir bottom absorption in the response of dams due to horizontal and vertical components of ground motion are investigated.
Load spectra for slender offshore structures in waves and currents
Authors: Taylor R. Eatock , Rajagopalan A. 
Published: March 2007

AbstractThe influence of currents on the wave induced dynamic response of offshore structures with slender members is assessed by deriving appropriate load spectra. The analysis permits the implications of the modified Morison equation to be examined, and suggests that methods of equivalent linearization commonly employed may yield unconservative results. An alternative formulation is proposed, in which the equations of motion are linear in the structural kinematics but the non‐linear dependence of drag force on fluid particle motions is retained. This leads to a load spectral density matrix expressed as a sum of terms, involving convolutions of the wave kinematics spectra. Results are obtained for a plane frame idealization of an offshore jacket structure. These demonstrate the strong influence of current, and the importance of retaining in the loading terms up to the third power of wave particle velocity.
Vibration of thermally stressed polar orthotropic annular plates
Authors: Gorman D. G. 
Published: March 2007

AbstractThis study sets out to analyse the effect of uniform temperature on the natural frequencies of transverse vibration of uniform polar orthotropic annular plates. The method employed is that of the annular finite element technique whereby the flexural and membrane components of the solution are separated. By close examination of the form of the resulting in‐plane stress distribution due to the thermal loading, it has been possible to obtain results for a wide selection of specimens by way of one equation and three graphs.
Effect of topography and subsurface inhomogeneity on seismic rayleigh waves
Authors: Ohtsuki Akira , Yamahara Hiroshi , Harumi Kasaburo 
Published: March 2007

AbstractThe effect of topography and subsurface inhomogeneity on surface motion is investigated in the case of Rayleigh waves. In the previous paper, the same effect was investigated in the case of SV waves. Several types of topography, such as cliffs both with and without a soft layer at the foot of the slope, are considered. Computations are made using a new hybrid method combining a particle model with a finite element method. In cases of harmonic Rayleigh waves, surface motions with amplitudes as large as 1.5 to 5 times the horizontal surface displacement of the incident Rayleigh waves are produced near the slope and the sloping interface. When a Rayleigh wave propagating through a hard single‐layered ground encounters a sloping interface where hard ground and soft ground make contact with each other, Rayleigh waves having two different, phase velocities are produced and they correspond to the fundamental mode, and the first mode determined by Haskell's method. In addition, the transient response when Rayleigh waves propagate through the cliff is also simulated. Assuming the vertical component of the Tokachi‐oki Earthquake (1968) measured on the surface to be a Rayleigh wave, the incident Rayleigh wave can be obtained by a Fourier synthesis of eigenfunctions of Rayleigh waves.
Dynamic response of 3‐D rigid surface foundations by time domain boundary element method
Authors: Karabalis D. L. , Beskos D. E. 
Published: March 2007

AbstractThe dynamic response of three‐dimensional rigid surface foundations of arbitrary shape is numerically obtained. The foundations are placed on a linear elastic, isotropic and homogeneous half‐space representing the soil medium and are subjected to either external dynamic forces or seismic waves of various kinds and directions, with a general transient time variation. The problem is formulated in the time domain by the boundary element method and the response is obtained by a time step‐by‐step integration. Two examples dealing with three‐dimensional rectangular foundations are presented in detail, together with comparisons with other methods, in order to document the accuracy of the method. The main advantages of the proposed method are that, unlike frequency domain techniques, it provides directly the transient response and forms the basis for extension to the case of non‐linear behaviour.
Effect of epicentral direction on seismic response of asymmetric buildings
Authors: Di Paola M. , Muscolino G. 
Published: March 2007

AbstractThe paper deals with the influence of the epicentral direction on the displacement and stress response of multistorey asymmetric buildings to earthquake horizontal ground motion.A method is given for computing for each plane frame of the complex structure a particular direction of the bidirectional stationary random input for which the horizontal floor displacement of the given frame is maximized. It is shown that this direction can be considered conservative for the corresponding non‐stationary process.
Cladding influence on dynamics response of tall buildings
Authors: Palsson Hafsteinn , Goodno Barry J. , Craig James I. , Will Kenneth M. 
Published: March 2007

AbstractPrecast concrete panels form attractive facades for steel frame buildings and are generally regarded as non‐structural by structural engineers. However, panels have been found to add lateral stiffness until their capacity or that of their connections is exceeded. Consequently, the computed dynamic response based on a model of the structural framing alone may be quite different from that experienced by the actual structure.As a case study, the influence of precast concrete panels on lateral and torsional stiffness of a 25‐storey building was investigated. The effect of cladding on dynamic properties and linear seismic response was explored by varying panel stiffness. Cladding stiffness was added to the bare frame model until analytical frequency values matched vibration test results. Then, using the cladding stiffness values obtained, an accidental eccentricity between centres of mass and rigidity at each floor level was imposed and linear seismic response computed. Torsional response effects were increased substantially. Finally, a modified cladding panel connection was developed based on previously‐reported studies for panelized construction. The influence of the proposed connection on overall structural response was determined for different ground motion inputs.
An alternative approach to the random response of bilinear hysteretic systems
Authors: Asano Koichiro , Iwan Wilfred D. 
Published: March 2007

AbstractAn analytical representation of the bilinear hysteretic characteristic is presented. Using this representation, the response of a single‐degree‐of‐freedom bilinear hysteretic system subjected to non‐stationary random excitation is examined by equivalent linearization. An ordinary differential equation is derived for the covariance matrix of the response. Numerical examples are presented and the accuracy of the approach is demonstrated. Extension of the approach to a wider class of hysteretic systems is discussed.
Earthquake response of structures with partial uplift on winkler foundation
Authors: Yim Chik‐Sing , Chopra Anil K. 
Published: March 2007

AbstractThe effects of transient foundation uplift on the earthquake response of flexible structures are investigated. The structural idealization chosen in this study is relatively simple but it incorporates the most important features of foundation uplift. In its fixed base condition the structure itself is idealized as a single‐degree‐of‐freedom system attached to a rigid foundation mat which is flexibly supported. The flexibility and damping of the supporting soil are represented by a Winkler foundation with spring‐damper elements distributed over the entire width of the foundation. Based on the response spectra presented for several sets of system parameters, the effects of foundation‐mat uplift on the maximum response of structures are identified. The influence of earthquake intensity, structural slenderness ratio, ratio of foundation mass to structural mass, foundation flexibility and p‐δ effects on the response of uplifting structures is also investigated.
Seismic analysis of a rotor‐bearing system
Authors: Srinivasan V. , Soni A. H. 
Published: March 2007

AbstractThe seismic analysis of a rotor‐bearing system is presented in the time domain. The governing equations of motion for the rotor are derived including the effects of rotatory inertia, shear deformation, gyroscopic effects, axial force, axial torque, stiffness and damping provided by the lubricants in the bearings, base translation and base rotation. A simple and efficient finite rotor element based on a Galerkin formulation is proposed to model the rotor. The effects of disks and flywheels mounted on the rotor are also included in the analysis. An example problem for a rotor‐bearing system is solved using El Centro earthquake data. Four cases are investigated that will permit one to study the influence of spin, base rotation, comparison between rigid body model and beam model and the influence of axial force and axial torque. The results of the above study show that the gyroscopic effects amplify the response of the rotor‐bearing system. The base rotations of the rotor‐bearing system under seismic excitation contribute significantly to the response.
A linear mathematical model for the seismic inplane behaviour of brick masonry walls part 1: Theoretical considerations
Authors: Mengi Yalcin , Sucuoǧlu Haluk , McNiven Hugh D. 
Published: March 2007

AbstractIn this study two mathematical models are presented for the linear dynamic behaviour of masonry walls. The study is completed in three stages: experimental observations, selection of a mathematical model and the determination of model parameters through optimization analysis. In the present paper (Part 1) the theoretical analysis used in the development of the mathematical models is presented. Part 2 is devoted to the optimization analysis.Evaluation of the experimental data, which is described in detail in Part 2, indicates that the first two modal frequencies of the wall specimen are close to each other. This may be attributed, on physical grounds, to strong interaction between the brick and mortar phases of the wall. Accordingly, a two‐phase mathematical model, namely a mixture model (MM), is chosen to describe the wall behaviour because it can differentiate between the two phases of the wall and take into account the interaction between them. The equations of MM are put into a discrete form to simplify the optimization analysis. As a special case, MM contains a simple one‐phase model called the effective modulus model (EMM). The equations of EMM are also established. Finally, the theoretical complex frequency response functions (CFRF) predicted by MM and EMM are obtained. CFRF relates the top acceleration of the wall to its base acceleration and is the response quantity chosen to be matched in the optimization analysis.
A linear mathematical model for the seismic inplane behaviour of brick masonry walls part 2: Determination of model parameters through optimization using experimental data
Authors: Sucuoǧlu Haluk , Mengi Yalcin , McNiven Hugh D. 
Published: March 2007

AbstractThe parameters appearing in the mixture and effective modulus models proposed in Part 1 are determined through optimization by matching theoretical and experimental responses. The optimization analysis is performed in frequency space. The response quantities chosen to be matched are the complex frequency response functions (experimental and theoretical) relating the Fourier transforms of top and base accelerations of the wall. Computations in optimization analysis are carried out by introducing an object (error) function and minimizing it using the Gauss‐Newton method. The results show that the mixture model is capable of predicting accurately the dynamic response of masonry walls up to a frequency which is well above the second modal frequency, whereas the effective modulus model describes the wall behaviour only up to the first modal frequency. Furthermore, it is shown that the mixture model is still valid when micro cracks, which may exist between the mortar and brick constituents, are present.
Dynamic‐stiffness matrix of soil by the boundary‐element method: Conceptual aspects
Authors: Wolf John P. , Darbre Georges R. 
Published: March 2007

AbstractStarting from a weighted‐residual formulation, the various boundary‐element methods, i.e. the weighted‐residual technique, the indirect boundary‐element method and the direct boundary‐element method, are systematically developed for the calculation of the dynamic‐stiffness matrix of an embedded foundation. In all three methods, loads whose analytical response in the unbounded domain can be determined are introduced acting on the continuous soil towards the region to be excavated. In the weighted‐residual technique and in the indirect boundary‐element method, a weighting function is used; in the latter case, it is selected as the Green's function for the surface traction. In the direct boundary‐element method, the surface traction along the structure‐soil interface is interpolated. The same type of boundary matrices which have a clear physical interpretation are identified in the three formulations, each of which is illustrated with a simple static example.The indirect boundary‐element method leads to the most accurate results. The guaranteed symmetry and the fact that the displacement arising from the applied loads can easily be calculated and compared to the prescribed displacement makes the indirect boundary‐element method especially attractive for calculating the dynamic‐stiffness matrix of the soil.Instead of calculating the dynamic‐stiffness matrix of the embedded foundation with the boundary‐element method, it can be determined as the difference of those of the regular free field and of the excavated part. The calculation of the former does not require the Green's function for the surface traction. The dynamic stiffness of the excavated part can be calculated by the finite‐element method.
On the solution of approximated systems when using reduced component modes
Authors: Martin K. F. , Ghlaim K. H. 
Published: March 2007

AbstractThe work described in this paper relates to the computation of vibrational characteristics of a system which consists of components connected together elastically. The vibrational characteristics of each component are known and these are used via matrix manipulation to find the system characteristics. This particular paper confines itself to examining the matrix manipulation in detail and it is shown that the mass normalized modal matrix [Ψ] and connection matrix [C] can be contracted in size without affecting the overall solution. When the system is approximated by deleting rows and columns from the involved matrices, it is confirmed analytically that which rows are deleted from the mass normalized modal matrix [Ψ] has no relevance to the approximate solution for the system.
Response to wind of a model chimney with added damping
Authors: Dosanjh H. , Johns D. J. 
Published: March 2007

AbstractSome ad hoc studies are reported which investigated the use of added damping layers at the base of a wind‐tunnel model of a chimney as a means of increasing its overall structural damping. Significant increases in the logarithmic decrement were obtained from decaying free‐vibration tests and in subsequent wind‐tunnel tests corresponding decreases in wind‐excited tip response were measured.It was concluded that the technique is promising for wind‐tunnel parametric studies in which significant changes in the structural damping are required and recommends further work.
A comparison of approximate techniques for non‐linear seismic soil response
Authors: Corsanego Alfredo , Solari Giovanni , Stura Dino 
Published: March 2007

AbstractSome equivalent linearization techniques, applicable to problems dealing with non‐linear seismic amplification of layered soils, are systematically treated and critically compared in this paper. The discussion concerns, in particular, the theoretical consistency, the operative modalities, the computational complexity and the numerical reliability of these methods.A comparison is made between the results furnished by some techniques among those examined and the results obtained through a step‐by‐step integration of the non‐linear equations of motion, assuming as a test‐problem the one‐dimensional amplification of a horizontally stratified soil deposit characterized by the Ramberg‐Osgood constitutive model.
The generation of spectrum compatible accelerograms for the design of nuclear power plants
Authors: Preumont André 
Published: March 2007

AbstractBased on the main features of the computer program THGE, the paper reviews the techniques which are available for the construction of an accelerogram whose response spectrum matches a design spectrum. First, a sample accelerogram is generated as the product of the stationary random sequence by a deterministic shape function. It is assumed that the spectral properties of the stationary process have been determined in a previous step, in order to lead to the design spectrum as expected maximum responses of a set of single degree of freedom oscillators. The principal properties of the Fast Fourier Transform which is used for this first step are reviewed. The paper then describes the procedures which are available, both in the frequency domain and in the time domain, to improve the agreement between the response spectrum and the target. It also discusses some related issues, such as the response spectrum calculations, the statistical dependence between the three earthquake components, the duration of the time history, the variability of the secondary response to various samples and the generation of an accelerogram whose response spectra envelop a set of design spectra. The point of view adopted is the one of the structural engineer.
Use of ritz vectors in wave propagation and foundation response
Authors: Bayo E. P. , Wilson E. L. 
Published: March 2007

AbstractThe accuracy of a numerical method is demonstrated for the dynamic analysis of large complex finite element systems in which the spatial distribution of the loading is constant. The method is based on the use of a special class of Ritz vectors which were previously proposed and can be generated with minimum numerical effort. The purpose of this paper is to extend the use of these vectors to the solution of wave propagation and foundation response problems.The method is applied to one‐, twoand three‐dimensional problems in order to illustrate the efficiency and accuracy of the technique. Unless it is necessary to evaluate the very high‐frequency behaviour of a structural system, it is shown that a small number of Ritz vectors will produce excellent results. Therefore, they can be very effective in the solution of three‐dimensional soil‐structure systems subjected to earthquake loading.
Complex response analysis of shells of revolution including uniform base translation and rocking
Authors: Lee Bor‐Jen , Gould Phillip L. 
Published: March 2007

AbstractA complex response algorithm for the dynamic analysis of axisymmetric thin shells supported on an interactive foundation is developed. The substructure deletion method is employed through the utilization of a dynamic boundary system at the contact area between the superstructure and the substructure. A new mathematical formulation in conjunction with the shell behaviour is developed to deal with rigid body motions due to the negation of the fixed base assumption. Four foundation conditions, that is, a fixed base, two pile foundation cases and a flexible base, are to examine the effect of base flexibility on the seismic response of cooling towers. Also, excellent comparative results between the frequency domain solution and a time domain solution are obtained.
Efficient analysis of dynamic response of linear systems
Authors: Veletsos Anestis S. , Ventura Carlos E. 
Published: March 2007

AbstractAfter reviewing briefly a recently proposed procedure for evaluating the dynamic transient response of a classically damped linear system from its corresponding steady‐state response, a modified procedure is presented which also appears to be highly efficient for non‐classically damped systems of the type encountered in studies of soil‐structure interaction. The concepts involved are developed by reference to viscously damped single‐degree‐of‐freedom systems, and numerical solutions are included to illustrate the accuracy and efficiency of the proposed procedure and its superiority over the classical Discrete Fourier Transform approach.