bluuebunny/crossref_metadata_2025_split huggingface dataset:
Base isolation by free rolling rods under basement
Authors: Lin Tsung‐Wu , Hone Chao‐Chi 
Published: April 2007

AbstractA new base isolation method is proposed for the protection of structures. Because of the efficiency of the isolation devices, the isolated structure may be made to remain elastic throughout major earthquakes. This device consists of two sets of mutually orthogonal free rolling rods under the basement of the structure. Since the coefficient of rolling friction of the rods is very small in practice, the structure can be isolated excellently from the support excitation. In this paper, the analytical method and the response of the isolated system for different parameters, such as the periods of the structure, the coefficient of rolling friction and the masses of rolling rods, are presented. The results indicate that the proposed method is excellent in isolating the structure from support excitations, as expected.
An indirect boundary element method applied to simulate the seismic response of alluvial valleys for incident P, S and Rayleigh waves
Authors: Sánchez‐Sesma F. J. , Ramos‐Martínez J. , Campillo M. 
Published: April 2007

AbstractA boundary integral formulation is presented and applied to model the ground motion on alluvial valleys under incident P, S and Rayleigh waves. It is based on integral representations for the diffracted and the refracted elastic waves using single‐layer boundary sources. This approach is called indirect BEM in the literature as the sources' strengths should be obtained as an intermediate step. Boundary conditions lead to a system of integral equations for boundary sources. A discretization scheme based on the numerical and analytical integration of exact Green's functions for displacements and tractions is used. Various examples are given for two‐dimensional problems of diffraction of elastic waves by soft elastic inclusion models of alluvial deposits in an elastic half‐space. Results are displayed in both frequency and time domains. These results show the significant influence of locally generated surface waves in seismic response and suggest approximations of practical interest. For shallow alluvial valleys the response and its resonant frequencies are controlled by a coupling mechanism that involves both the simple one‐dimensional shear beam model and the propagation of surface waves.
Damped resonant appendages to increase inherent damping in buildings
Authors: Villaverde Roberto , Koyama Leslie A. 
Published: April 2007

AbstractIt is demonstrated that the addition of a tuned mass‐spring‐dashpot system with a relatively small mass and a high damping ratio can be an effective way to increase the inherent damping characteristics of buildings and reduce, thus, their response to earthquake excitations. The demonstration is based on a theoretical formulation and on numerical and experimental studies that confirm this formulation. In the theoretical formulation, it is shown first that, if certain conditions are satisfied, the damping ratios in two of the modes of the system that is formed by a building and an appendage in resonance are approximately equal to the average of the corresponding damping ratios of the building and the appendage. Based on this finding, it is then shown that an attached appendage with a high damping ratio and tuned to the fundamental frequency of a building may increase the damping ratio in the fundamental mode of the building to a value close to half the damping ratio of the appendage. In the numerical study, the response of a ten‐storey shear building is analysed under two different earthquake ground motions with and without the proposed resonant appendages. Appendages with damping ratios of 20 and 30 per cent are considered. In this study, it is found that under one of the ground motions the maximum displacement of the building's roof is reduced 30 per cent with the appendage with 20 per cent damping and 39 per cent with the one with 30 per cent damping. Similarly, with these two appendages the building's base shear is reduced 31 and 41 per cent, respectively. In the experimental study, a wooden three‐storey structural model is tested in a shaking table with and without an appendage designed and constructed to have a damping ratio of 53‐5 per cent. The test is conducted under random and sinusoidal base excitations. In the shaking table test under random excitation, the attached appendage reduces the response of the model 38‐6 per cent, while in that under sinusoidal vibration 45‐2 per cent.
Modelling of material non‐linearities in steel structures subjected to transient dynamic loading
Authors: Elnashai A. S. , Izzuddin B. A. 
Published: April 2007

AbstractThis paper is concerned with the modelling of the behaviour of steel under cyclic and dynamic loading conditions. After a general discussion regarding the requirements for accurate and efficient modelling in dynamics, two models are described and implemented. The bilinear stress‐strain constitutive relationship with kinematic hardening is widely used in many computer codes, hence is used for ‘control’ purposes. The multisurface plasticity model is said to exhibit the important qualities of strain hardening, softening and relaxation to a mean stress. This model is described in detail and notes on model parameter evaluation are given. A number of validation examples are presented, due to the complexity of implementation of the multisurface formulation. This is followed by comparisons between the bilinear response predictions and those of the multisurface model for cyclic and dynamic tests on beam‐columns. It is concluded that in the absence of material test data under cyclic loading, the bilinear model provides acceptably accurate response predictions. However, the multisurface model provides a significantly closer fit to experimental results, due to its ability to model a yield plateau and a non‐linear strain‐hardening regime as well as cyclic degradation. It can also be used for new types of steel where no distinct yield point is observed.
A hybrid modelling of soil–structure interaction problems for deeply embedded structures in A multilayered medium
Authors: Romanel Celso , Kundu Tribikram 
Published: April 2007

AbstractDynamic response of deeply embedded structures, such as underground tunnels and deep foundations, in a multilayered elastic half‐space are analysed when the structure is excited by a plane P or SV wave propagating at some angle. The scattered field is represented by the sum of three Green's functions, corresponding to two oscillating forces and one oscillating moment at the centroid position of the buried structure. The amplitudes of these two forces and one moment are a priori unknown and are obtained by satisfying displacement and stress continuity conditions across the near‐field/far‐field boundary. The distinguishing feature of this technique from direct or indirect boundary integral techniques is that in these techniques a distribution of sources of unknown amplitude are considered at the near‐field/far‐field boundary, and a large number of sources are needed for different combinations of source‐receiver arrangements. But in this technique the sources of unknown amplitude are placed at the location of the structure, not at the near‐field/far‐field boundary and, using the Saint Venant's principle, the scattered field is modelled. Thus, the number of sources required is reduced to only three. Two example problems are solved. The first one is for a deeply embedded footing in a three‐layer soil mass and the second one is for a rectangular tunnel in a two‐layer soil mass.
Linear system response by DFT: Analysis of A recent modified method
Authors: Hall John F. , Beck James L. 
Published: April 2007

AbstractAn analysis of a recent modified frequency‐domain procedure for computing the response of linear systems using the fast Fourier transform (FFT) algorithm is described. This modified procedure eliminates the appended free‐vibration interval that is used in the standard approach. The duration of the period of computation still needs to be longer than that of the response interval of interest, but only slightly. Reducing the period of computation lowers the number of frequencies at which the transfer function needs to be defined. The major drawback of the method is a high sensitivity to errors in the computed values of the transfer function, which reduces the role of interpolation in the transfer function definition. The modified method is related to the discrete Laplace transform.
Dynamic behaviour and seismic response of El Infiernillo dam
Authors: Elgamal Ahmed‐W. M. , Gunturi Ramana V. 
Published: April 2007

AbstractEl Infiernillo, a 145 m high rockfill dam in Mexico built in a narrow V‐shaped canyon, was subjected to eight major earthquakes since its construction. In this study, the dynamic dam response is analysed using (i) the recorded November 15, 1975 bedrock‐crest acceleration histories and (ii) the results of a 1970 full‐scale test conducted by UNAM, in which eight upstream–downstream and longitudinal resonant frequencies and configurations were observed and documented. These observed and seismically induced dynamic responses are compared herein to predictions of two different numerical models of El Infiernillo dam; a newly developed simplified three‐dimensional (3D) model, and a 3D finite element model. The dynamic dam response characteristics are assessed, and performance of the employed numerical models is evaluated. It is found that (i) higher modes of vibration had participated significantly in the recorded seismic response and (ii) upstream–downstream response is well represented by the two numerical models employed. Using the simplified model, the September 19, 1985 earthquake non‐linear response is computed and shown to compare satisfactorily with its recorded counterpart in the upstream‐downstream and vertical directions. The largest computed dynamic accelerations, stresses and strains are found to occur within the upper third of the dam body.
A modal combination rule for spatially varying seismic motions
Authors: Berrah Mounir K. , Kausel Eduardo 
Published: April 2007

AbstractThe spatial variability of seismic ground motion is an important aspect for the earthquake resistant design of extended facilities. A modified response spectrum model, which addresses the problem of multiply supported structures subjected to imperfectly correlated seismic excitations, has already been developed (see References 1 and 2). The present paper proposes a modal combination rule for the case of non‐uniform seismic input, which would be used together with the modified response spectrum model in order to compute physical responses. This rule, which accounts for modal cross‐correlations, is an extension to an existing rule for the case of uniform seismic motions. It modifies the existing modal cross‐correlation coefficients through a correction factor which depends on structural properties and on the characteristics of the wave propagation phenomenon. Finally, some practical considerations on the theoretical development are addressed. They aim at suggesting reasonable simplifications which render the modal combination rule more appealing for engineering purposes. The proposed practical combination rule is validated through a numerical experiment which also characterizes the effect of non‐uniform seismic input on modal cross‐correlation.
Results from field testing A curved box girder bridge using simulated earthquake loads
Authors: Richardson James A. , Douglas Bruce M. 
Published: April 2007

AbstractThis paper presents the results of a unique field test on a curved highway overpass. In the test, large horizontal loads were applied to the superstructure of the bridge and quickly released, causing the bridge to vibrate. The resulting large‐amplitude vibrations were intended to be similar to the vibrations caused by earthquakes (horizontal accelerations of up to 25 per cent of gravity were measured on the bridge deck). Well‐defined lateral, longitudinal, vertical and torsional vibration modes were identified from the test data.The vibration modes were used to verify an analytical model of the bridge's dynamic response. For this paper, the model was verified using only the fundamental vibration mode, which was primarily a horizontal vibration mode. Using a system identification procedure, the dynamic response model was adjusted until its frequency and mode shape matched the measured frequency and mode shape. Parameters in the verified model were compared with the same parameters calculated from information in the structural drawings. Because the fundamental mode represents a horizontal mode, the bridge parameters identified in this paper were those parameters which strongly influence the horizontal response of the bridge.
Green's function of support‐excited structures with tuned‐mass dampers derived by A perturbation method
Authors: Tsai Hsiang‐Chuan 
Published: April 2007

AbstractA tuned‐mass damper is a small damped spring‐mass system which vibrates in resonance with the main structure to which it is attached so as to be able to dissipate vibration energy and reduce the structural response. In this paper, explicit forms of Green's function for the transient response of main structures equipped with the tuned‐mass damper and subjected to support excitation are derived by perturbation techniques and provide an insight into the characteristics of the damper. It is found that there exists a critical damping level for the tuned‐mass damper. If the damper damping is higher than this critical damping level, increasing the damper damping will enhance the structural response. When the damper damping is below this critical value, something called ‘beat phenomenon’ occurs where the structure will have a smaller response in the first beat cycle, but have a higher rebound in the following beat cycles.
Earthquake response of tension‐leg‐platforms in steady currents
Authors: Venkataramana Katta 
Published: April 2007

AbstractDynamic response of tethers of tension‐leg‐platforms to current and horizontal earthquake excitations is investigated. The static deflected shape of tether under a steady current is firstly identified. Next dynamic analysis for earthquake input is carried out for this deflected tether. The fluid loading due to surrounding water is included in the analysis as an added mass term and a hydrodynamic damping term. The tether is discretized by lumping masses at selected nodes. The platform is represented by a mass at the top end of the tether. The effect of pretension in the tether is taken into account in the form of a geometric stiffness term. At each node three degrees of freedom corresponding to surge, heave and pitch motion are considered. As the vibration modes and hence the responses are likely to be affected by the foundation characteristics, the study is extended to include the dynamic soil–structure interaction. The dynamic equations of motion for the tether–pile–soil system are derived using the substructure method. The natural frequencies and the vibration mode shapes of the total system are determined by eigenvalue analysis. The input ground acceleration is represented by Tajimi–Kanai's power spectrum for stationary conditions. The response analysis is carried out using the frequency‐domain random‐vibration approach. The coupled axial and lateral responses are evaluated for horizontal ground excitations. Numerical results indicate that the horizontal displacements of the tether increase with the input ground acceleration, but are nearly equal for all the cases of current velocities considered in the study; the vertical displacements however increase rapidly with the increase in current velocity. For the model considered in the present study, the responses are reduced when soil–structure interaction is included in the analysis.
Effect of transverse load‐resisting elements on inelastic earthquake response of eccentric‐plan buildings
Authors: Correnza J. C. , Hutchinson G. L. , Chandler A. M. 
Published: April 2007

AbstractThe accurate evaluation of code torsional provisions for plan‐eccentric structures exhibiting inelastic response relies on the adoption of appropriate systems defining both the torsionally balanced (reference) and torsionally unbalanced cases. Whilst a considerable number of analytical studies of this problem have been presented in the literature, inconsistencies have arisen in their conclusions. It is evident from a review of previous studies that one factor contributing significantly to these discrepancies arises in the definition of the structural layout. An issue of particular importance is whether the transverse load‐resisting elements oriented perpendicular to the assumed (lateral) direction of earthquake loading should, for purposes of realism, be included in model definitions. Given the diverse approaches in the existing literature, clarification of this issue is required in order to advance the understanding of inelastic torsional response behaviour and to assist the interpretation and comparison of previous studies. This paper aims to provide such clarification, based on analyses of a series of models defined rigorously according to code design provisions. Such models have been subjected to both uni‐ and bi‐directional ground motion input. It is concluded that for the flexible‐edge element, accurate estimates of additional ductility demand arising from torsional effects may be obtained from uni‐directional models (in which both the transverse elements and the corresponding earthquake component are neglected) only for medium‐period to long‐period systems. Such estimates may be over‐conservative for short‐period systems, which constitute a large proportion of systems for which code static torsional provisions are utilized. It is further concluded that models incorporating the transverse elements but analysed under uni‐directional lateral loading may underestimate by up to 100% the torsional effects in such systems, but are reasonably accurate for medium‐ and long‐period structures.
Soil–pile interaction during the passage of rayleigh waves: An analytical solution
Authors: Makris Nicos 
Published: April 2007

AbstractA simple analytical solution is presented to calculate the single‐pile response when excited by the passage of Rayleigh seismic waves. Closed‐form expressions for the horizontal and vertical displacement distributions are presented for piles with finite or infinite length. The analytical results for both free‐head and fixed‐head piles are obtained through a dynamic Winkler model, with realistic frequency‐dependent ‘springs’ and ‘dashpots’. The results of the presented method are in excellent agreement with results of a rigorous solution. It is shown that in vertical motion, the differences between pile and soil displacements are far more significant than in horizontal motion, and therefore, further work is needed to investigate the importance of pile‐soil‐pile interaction (group effects), because of the vertical component of Rayleigh seismic waves.
Dynamic stiffness matrices for two circular foundations
Authors: Liou Gin‐Show 
Published: April 2007

AbstractA systematic procedure is presented for generating dynamic stiffness matrices for two independent circular foundations on an elastic half‐space medium. With the technique reported in References 1–3, the analytic solution of three‐dimensional (3D) wave equations satisfying the prescribed traction due to the vibration of one circular foundation can be found. Since there are two analytic solutions for two prescribed tractions due to the vibrations of two circular foundations, the principle of superposition must be used to obtain the total solution. The interaction stresses (prescribed tractions) are assumed to be piecewise linear in the r‐directions of both cylindrical co‐ordinates for the two circular foundations. Then, the variational principle and the reciprocal theorem are employed to generate the dynamic stiffness matrices for the two foundations. In the process of employing the variational principle, a co‐ordinate transformation matrix between two cylindrical co‐ordinate systems is introduced. Some numerical results of dynamic stiffness matrices for the interaction of two identical rigid circular foundations are presented in order to show the effectiveness and efficiency of the present method, and some elaborations for its future extensions are also discussed.
Dynamic in‐plane racking tests of curtain wall glass elements
Authors: Pantelides C. P. , Behr R. A. 
Published: April 2007

AbstractAttention has been paid recently to the potentially serious life safety and economic loss issues related to the seismic performance of ‘architectural,’ or ‘non‐structural’ building elements such as glass lites in curtain wall systems. In response, a pilot study was undertaken at the University of Missouri‐Rolla to investigate the dynamic racking performance of a 15·6 × 12·0 ft (4·56 × 3·68 m) section of curtain wall containing three 5 × 6 ft (1·52 × 1·84 m) glass panels. The curtain wall system was a ‘wide mullion’ design that had generous 1 in (25 mm) clearances between glass edges and the aluminium glazing pocket. Dynamic racking tests were performed totally in plane; no out‐of‐plane or torsional motions were included. Various types of glass specimens were tested, including annealed, heat‐strengthened and fully tempered glass in monolithic and laminated configurations. Dry glazed and two‐side structural silicone curtain walls were tested. Test results for dry glazed specimens showed that annealed and heat‐strengthened laminated glass experienced no fallout whatsoever. By contrast, annealed monolithic glass experienced frequent fallout in both small and large shards. Fully tempered monolithic glass experienced dicing, which resulted in occasional fallout of entire glass lites. Loss of rigidity in fully tempered laminated glass (when both glass plies were broken) occasionally caused entire lites to fall out. Polyester film (not anchored to the mullions) was applied to annealed monolithic glass; it prevented small shards from falling out, but sometimes contributed to entire lite fallout after the onset of severe glass cracking. Annealed laminated glass units with two‐side structural silicone glazing exhibited only very minor glass damage and no glass fallout.
Dynamic‐stiffness matrix of unbounded soil by finite‐element multi‐cell cloning
Authors: Wolf John P. , Song Chongmin 
Published: April 2007

AbstractTo calculate the dynamic‐stiffness matrix of the unbounded soil, a multi‐cell cloning algorithm based solely on the finite‐element formulation is developed. A non‐linear system of equations has to be solved iteratively once for the whole range of frequency. For a specific frequency, two‐ and three‐cell cloning lead to highly accurate results, which is demonstrated by examples of increasing complexity.
Dynamic displacements and stresses in the vicinity of a cylindrical cavity embedded in a half‐space
Authors: Luco J. E. , de Barros F. C. P. 
Published: April 2007

AbstractThe two‐dimensional response of a viscoelastic half‐space containing a buried, unlined, infinitely long cylindrical cavity of circular cross‐section subjected to harmonic plane SH, P, SV and Rayleigh waves is obtained by an indirect boundary integral method based on the two‐dimensional Green's functions for a viscoelastic half‐space. An extensive critical review of the existing numerical results obtained by other techniques is presented together with some new numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity for P, SV, SH and Rayleigh waves.