bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transients in cylindrical shells
Authors: Thambiratnam D. P. , Shah A. H. , Cohen H. 
Published: March 2007

AbstractThe propagation of non‐axially symmetric transients in linear, elastic, isotropic and homogeneous cylindrical shells subjected to impulsive boundary loads is treated in this paper. Expressing the displacement components in the form of a Fourier series in the circumferential co‐ordinate, the displacement equations of motion are written for each harmonic.The analysis is based on the concept of a wave as a carrier of discontinuities in the field variable and its derivatives. These discontinuities are determined from a set of recurrence relations which are in turn generated by the use of time‐harmonic asymptotic series solutions to the equations of motion. The method is illustrated by presenting detailed numerical results pertaining to the influence of earthquake or blast‐induced ground excitation on cylindrical tanks.
Seismic dynamic response by approximate methods
Authors: Bieber Ray E. , Hovland H. John 
Published: March 2007

AbstractCurrent seismic safety evaluation for earth dams relies on approximate methods of analysis for prediction of non‐linear, transient, dynamic response. One of these approximate methods uses a Strain Reduction Factor (SRF), and has been widely applied in a variety of one‐dimensional and two‐dimensional soil structural analyses. A second method considered, Equivalent Temporal Damping (ETD), has been previously applied to several seismic dynamic analyses of earth dams. The relative accuracy of the two methods is assessed by comparing them with incremental plasticity, nearly exact numerical solutions. For a simple shear element subjected to deterministic and non‐stationary random input accelerations, a serious overprediction of the maximum peak shear response occurs by the SRF method, whereas the ETD results agree very closely with the incremental plasticity solutions. The SRF and ETD methods are also applied to seismic dynamic response analysis of a Vertical Soil Column system, and the same trends as established in the previous case are observed. It is concluded that, in lieu of combined incremental plasticity and finite difference or finite element numerical solutions, the ETD approach is the more accurate of the methods tested for seismic dynamic response analysis of earth dams.
Bridge dynamic loading due to road surface irregularities and braking of vehicle
Authors: Gupta R. K. , Traill‐Nash R. W. 
Published: March 2007

AbstractSingle span highway bridges of composite construction are idealized as beams as well as orthotropic plates. A standard HS–20–44 highway vehicle is represented by a planar, two‐axle, sprung mass system with frictional device. The response equations are derived in terms of the natural modal co‐ordinates of the bridge and of displacement co‐ordinates of the vehicle. The road surface irregularities, generally found at the junctions of the approach road and bridge ends, are idealized as a 45° ramp. The maximum impact factors for bending moment and deflection are obtained due to the ramp and in combination with the braking of vehicle for symmetric as well as essentric loading of the vehicle.
The estimation of earthquake‐generated additional tension in a suspension bridge cable
Authors: Irvine H. M. 
Published: March 2007

AbstractA simple formula, equation (15), is derived for the peak additional cable tension that can be expected in a suspension bridge undergoing earthquake excitation. The method involves application of the response spectrum technique and rests on several plausible assumptions. The formula gives a reasonable upper bound, suitable for preliminary design estimates, irrespective of whether the ground motions at each end are in‐phase or, as is probable with a long span bridge, whether they are out‐of‐phase.
Base isolation for torsion reduction in asymmetric structures under earthquake loading
Authors: Lee David M. 
Published: March 2007

AbstractThis paper examines the effectiveness of a bilinear hysteretic base isolation system in lowering the shear forces and torques generated in a structure by two‐way, translatory ground motions. The study is restricted to single‐storey, three‐dimensional structures having asymmetries in both horizontal directions and being excited by the El Centro (May 1940) earthquake motions.It is shown that with base isolation the structural torques are drastically reduced, even if the structural eccentricity is large. This reduction in structural torque is greatest when the isolation system's centre of stiffness coincides with the structure's centre of mass. The highly dissipative action of the isolation system provides strong modal decoupling which prevents the translational motions from resonantly driving the torsional motions. The maximum base displacements, due to both translation and rotation combined are less than 11 cm, which is well within the limits of currently available isolation system components.The dynamic action of the base isolation system is outlined and currently available isolation system components described.
Estimating inelastic response spectra from elastic spectra
Authors: Iwan W. D. 
Published: March 2007

AbstractInelastic displacement response spectra are determined for a broad class of single‐degree‐of‐freedom hysteretic structures. Based on these spectra, effective linear period and damping parameters are defined as a function of ductility. A simple empirical formula is derived which may be used to estimate the mid‐period range inelastic response spectrum of a general hysteretic structure given the linear response spectrum of the excitation. The estimates obtained from this formula are compared with those obtained by the Newmark‐Hall method, the substitute–structure method and the ATC–3 tentative procedure. It is found that the empirical formula not only gives good estimates of the average behaviour of the inelastic spectrum, but also reproduces some of the details of the spectrum.
Soil—foundation interaction and differential ground motions
Authors: Bycroft G. N. 
Published: March 2007

AbstractDifferential ground motions due to horizontally propagating surface waves are of importance in determining the stresses and displacements developed in extended structures such as large mat foundations for nuclear power stations, dams, bridges and pipe‐lines. A general method is developed for determining the motion of a large rigid mat foundation subjected to travelling surface waves and observations made on the relative displacements of individual foundations and their importance in bridge failure.
Vibrations of the elastic half‐space due to vertical surface loads
Authors: Holzlöhner U. 
Published: March 2007

AbstractThe displacements of the surface of the homogeneous elastic half‐space subjected to a vertical concentrated load acting at the surface are calculated. The solution is shown to approach Lamb's simple formula for the far‐field. The solution for the concentrated load can be used to calculate displacements due to distributed loads with high accuracy and economically. The results are applied to define the regions ‘near‐field’ and ‘far‐field’. Some near‐field phenomena are described.
Influence of geometry and of the constitutive law of the supporting columns on the seismic response of a hyperbolic cooling tower
Authors: Wolf J. P. , Skrikerud P. E. 
Published: March 2007

AbstractThe supporting columns and their foundation influence the cooling tower's seismic response decisively. At the same time, they represent the most vulnerable part of the structure. To determine the optimum seismic design, the influence of the geometry of the columns is investigated parametrically. The dominant parameter, the in‐plane angle of inclination, should be selected to be as large as possible. For a specific geometric configuration, the response for increasing seismic excitation is studied. The constitutive laws of the concrete and of the reinforcement steel in the columns as well as slipping and lift‐off of the foundations are incorporated into a non‐linear analysis. The largest reduction in response results from the behaviour of the columns in tension. The tower can thus withstand much larger seismic excitations than those indicated in a linear analysis. Slipping and lift‐off, which develop for extreme earthquakes only, play a less important role, even when occurring in the entire foundation.
Response of a circular cylindrical shell to disturbances in a half‐space
Authors: El‐Akily Nabil , Datta S. K. 
Published: March 2007

AbstractThe response of a circular cylindrical shell to disturbances in an elastic half‐space is the subject of this paper. Two methods of solution are presented. The first is a method of matched asymptotic expansions, and the second is a method of successive reflections.
Rocking response of rigid blocks to earthquakes
Authors: Yim Chik‐Sing , Chopra Anil K. , Penzien Joseph 
Published: March 2007

AbstractThis investigation deals with the rocking response of rigid blocks subjected to earthquake ground motion. A numerical procedure and computer program are developed to solve the non‐linear equations of motion governing the rocking motion of rigid blocks on a rigid base subjected to horizontal and vertical ground motion.The response results presented show that the response of the block is very sensitive to small changes in its size and slenderness ratio and to the details of ground motion. Systematic trends are not apparent: The stability of a block subjected to a particular ground motion does not necessarily increase monotonically with increasing size or decreasing slenderness ratio. Overturning of a block by a ground motion of particular intensity does not imply that the block will necessarily overturn under the action of more intense ground motion.In contrast, systematic trends are observed when the problem is studied from a probabilistic point of view with the ground motion modelled as a random process. The probability of a block exceeding any response level, as well as the probability that a block overturns, increases with increase in ground motion intensity, increase in slenderness ratio of the block and decrease in its size.It is concluded that probabilistic estimates of the intensity of ground shaking may be obtained from its observed effects on monuments, minarets, tombstones and other similar objects provided suitable data in sufficient quantity is available, and the estimates are based on probabilistic analyses of the rocking response of rigid blocks, considering their non‐linear dynamic behaviour.
Overturning effects in stiffened building frames
Authors: Huckelbridge Arthur A. , Ferencz Robert M. 
Published: March 2007

AbstractIn this paper seismically induced overturning effects in stiffened building frames are studied by examining the response of two structures: a 20‐storey ‘core wall’ reinforced concrete frame and a 10‐storey steel braced frame. The excitations utilized in the study are the 1971 Pacoima Dam S16E Record and the 1940 El Centro N‐S Record magnified by a factor of two. Non‐linear effects of the following types are considered: plastic hinging of beams and columns, yielding and/or buckling of bracing members and transient uplift of portions of the structures from the foundation. In particular, comparisions are made between response with unlimited base overturning capacity assumed and response with dead‐weight overturning resistance only. Providing dead‐weight overturning resistance only is shown to significantly reduce seismic load levels, with relatively little or no loss in drift control. Ductility demand in these stiffened frames is shown to be limited, when transient uplift is allowed, to the link beams connecting stiffened and unstiffened portions of the structures.
Modal methods in the dynamics of systems with non‐classical damping
Authors: Traill‐Nash R. W. 
Published: March 2007

AbstractWhen damping in a system is both significantly high and its distribution is non‐classical the solution of dynamical problems by conventional modal analysis is complicated by the presence of coupling between the normal co‐ordinates. Further, the convergence of a solution may be erratic with successive modal additions, leading to the need to include a larger number of modes than would otherwise be expected. In this paper methods of modal analysis in structural dynamics are discussed and their derivations briefly given. These include the conventional mode displacement method and the force summation method, employing normal modes, and the analogous procedures with damped modes. In the latter, dynamic response equations are not coupled. Dynamic loading solutions by the four approaches, each taking account of the non‐classical damping distribution, are demonstrated with a simple model representing a structure on a compliant foundation. The results strongly suggest that the use of damped modes with force summation could be the most effective procedure when damping is non‐classical.
Effect of earth media on the seismic motion of embedded rigid structures
Authors: Fedock Joseph J. , Schreyer Howard L. 
Published: March 2007

AbstractA finite element analysis is performed to determine the influence of the choice of a constitutive model for the earth medium upon the response to seismic waves of an embedded rigid structure. The seismic forcing function is characterized by Rayleigh waves with amplitude parameters adjusted to provide identical free‐field motion at a surface reference point for one particular sand represented with elastic, plastic and viscoelastic models. Within the limitations of the analysis, the result is that the steady‐state rigid body motions of the embedded structure are essentially identical for these constitutive relations and, consequently, it is appropriate to use an elastic representation for the earth medium.
Surface waves in a half‐space of submerged sand
Authors: Vardoulakis I. 
Published: March 2007

AbstractThe present analysis deals with harmonic Rayleigh‐type and transverse surface waves in a half‐space of incompressible material with constant density and with shear modulus linearly increasing with depth. This model is proposed for describing the response of a half‐space of submerged, dense sand to small strain vibrations of many cycles. It is shown that a discrete spectrum of polynomial solutions is always possible which makes the eigenvalue problem more tractable.
A response spectrum method for random vibration analysis of mdf systems
Authors: Kiureghian Armen Der 
Published: March 2007

AbstractA response spectrum method for stationary random vibration analysis of linear, multi‐degree‐of‐freedom systems is developed. The method is based on the assumption that the input excitation is a wide‐band, stationary Gaussian process and the response is stationary. However, it can also be used as a good approximation for the response to a transient stationary Gaussian input with a duration several times longer than the fundamental period of the system. Various response quantities, including the mean‐squares of the response and its time derivative, the response mean frequency, and the cumulative distribution and the mean and variance of the peak response are obtained in terms of the ordinates of the mean response spectrum of the input excitation and the modal properties of the system. The formulation includes the cross‐correlation between modal responses, which is shown to be significant for modes with closely spaced natural frequencies.The proposed procedure is demonstrated for an example structure that is subjected to an ensemble of earthquake‐induced base excitations. Computed results based on the response spectrum method are in close agreement with simulation results obtained from time‐history dynamic analysis. The significance of closely spaced modes and the error associated with a conventional method that neglects the modal correlations are also demonstrated.
Response spectrum techniques for three‐component earthquake design
Authors: Anagnostopoulos Stavros A. 
Published: March 2007

AbstractAn evaluation is made of response spectrum techniques as applied to seismic analysis and design of steel template offshore platforms. Such structures are designed as braced space frames for several loading conditions, including the simultaneous action of three earthquake components. Base shears as well as gross forces and combined stresses in members of three different platforms are computed for 30 real, three‐component earthquakes and response spectrum predictions, obtained by several modal‐spatial combination methods, are compared to time history solutions. Results are presented in the form of error statistics.The three approximations examined are: (a) combination of modes for one component input, (b) combination of the three partial responses to obtain estimates of total response and (c) combination of gross forces to derive maximum design stresses at a section. Attention is focused on corner piles because these are among the most heavily penalized members by three‐component excitations.It is shown that commonly used spatial combination rules may underestimate gross forces in design controlling corner members by 15–30 per cent on the average. This is attributed to correlations between motion components that create additive effects along certain directions. Typical estimates of combined stresses, however, are found to be slightly conservative.
Response of a circular cylindrical shell to disturbances in a half‐space—numerical results
Authors: El‐Akily Nabil , Datta S. K. 
Published: March 2007

AbstractIn this paper we present numerical results representing the response of an elastic cylindrical shell to disturbances in an elastic half‐space. These numerical results show the radial displacement at the middle surface of the shell and the hoop stress in the shell. The incident disturbance is in the form of a plane dilatational wave or a Rayleigh wave.
Generation of lateral and rotational floor response spectra by an alternative approach
Authors: Ishac Magdi F. , Heidebrecht Arthur C. 
Published: March 2007

AbstractA procedure is described to compute the lateral and rotational floor response spectra of an asymmetric reactor building structure without a time history analysis. The spectral values obtained by filtering the prescribed ground motion first through the structure and the resulting lateral‐rotational motions through simple oscillators are equal to the maximum lateral‐rotational responses of the structure developed when the order of filtration is reversed. Based on the preceding concept a deterministic method is presented to construct the lateral‐rotational floor response spectra utilizing the response spectrum technique.
Hydrodynamic and foundation interaction effects in frequency response functions for concrete gravity dams
Authors: Chopra Anil K. , Gupta Sunil 
Published: March 2007

AbstractThe linear response of idealized dam cross‐sections to harmonic horizontal or vertical ground motion is presented for a range of the important system parameters characterizing the properties of the dam, foundation rock and impounded water. Based on these frequency response functions, the separate effects of interaction between the dam and water and interaction between the dam and foundation, and the combined effects of the two sources of interaction, on dynamic response of dams are investigated.
Soil‐pile interaction in vertical vibration induced through a frictional interface
Authors: Akiyoshi T. 
Published: March 2007

AbstractThe interaction between a soil layer and an end bearing pile in vertical vibration induced through the frictional interface is theoretically investigated. The pile is assumed to be vertical and elastic, whereas the soil is considered as a linear visco‐elastic layer with hysteretic damping. Slip between the pile and the soil is allowed to occur along the frictional interface, in which the hysteretic frictional stress is linearized to permit modal decomposition. Approximate solutions of the pile and the soil for steady‐harmonic loads are obtained in closed form by composing the wave modes of the layer. The displacement amplitudes of the pile and the soil, the critical slip force, the stiffness of the pile head, and the modal stiffness contribution of the soil to the pile are evaluated numerically with respect to the ratio of applied force level to the slip stress level and the slenderness ratio, at various frequencies.
An engineering prediction model of acceleration response spectra and its application to seismic hazard mapping
Authors: Katayama Tsuneo 
Published: March 2007

AbstractA regression analysis was made on 277 acceleration response spectra computed from Japanese accelerograms by subdividing the data into discrete categories. Five magnitude and distance categories, and four ground condition categories were used. The maximum absolute acceleration amplitude is predicted as a product of three factors, each representing a weighting factor for magnitude, distance and ground condition category at each of the 18 response spectrum periods from 0·1 s to 4 s at a damping value of 5 per cent of critical. A method was then developed to evaluate seismic hazard in terms of acceleration response spectrum by using the prediction model and the seismicity data, and it was applied to obtain seismic macro‐zoning maps of Japan which are dependent on the natural period of a structure. The results of the analysis indicated that a single seismic zoning map may not be sufficient to cover a variety of structures with a wide range of periods because the expected spectral shape differs according to the seismicity of the area.
An imposed force summation method for non‐linear dynamic analysis
Authors: Dungar R. 
Published: March 2007

AbstractA method of obtaining the response of a non‐linear system is proposed, which involves imposing the solution upon the equations of motion for a linear system and solving using selected modes of vibration. Contribution from the remaining modes of the system is included in terms of their quasi‐static response. The method is developed and illustrated with reference to a system with material non‐linearity and special reference is given to the dynamic analysis of embankment dams.
A note on the perturbation analysis of the mode shapes of torsionally coupled buildings
Authors: Tsicnias T. G. , Hutchinson G. L. 
Published: March 2007

AbstractThe application of perturbation analysis in torsionally coupled buildings makes it possible to obtain an approximation of the dynamic properties of the buildings in question by combining appropriately the dynamic properties of the corresponding torsionally uncoupled buildings. This note aims to clarify the results obtained from a second‐order perturbation analysis of the mode shapes of torsionally coupled buildings. Numerical examples of building models are given to illustrate the theoretical points.
Seismic safety of reinforced concrete members and structures
Authors: Banon Hooshang , Veneziano Daniele 
Published: March 2007

AbstractBased on cyclic load tests of large‐scale reinforced concrete elements and assemblages, a probabilistic model of member failure is developed. The model gives the probability of survival at time t as a functional of damage ratio and dissipated energy up to t. After extension to multivariate survival of several members with correlated resistance, the model is used to calculate the safety of reinforced concrete frames subjected to given input motions. Results are in terms of the probability of local failure and of no failure anywhere in the system.