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Showing papers in "Earthquake Engineering & Structural Dynamics in 2002"


Journal ArticleDOI
TL;DR: Incremental dynamic analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads as mentioned in this paper, which involves subjecting a structural model to one or more ground motion record(s), each scaled to multiple levels of intensity, thus producing one (or more) curve(s) of response parameterized versus intensity level.
Abstract: Incremental dynamic analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. It involves subjecting a structural model to one (or more) ground motion record(s), each scaled to multiple levels of intensity, thus producing one (or more) curve(s) of response parameterized versus intensity level. To establish a common frame of reference, the fundamental concepts are analysed, a unified terminology is proposed, suitable algorithms are presented, and properties of the IDA curve are looked into for both single-degree-of-freedom and multi-degree-of-freedom structures. In addition, summarization techniques for multi-record IDA studies and the association of the IDA study with the conventional static pushover analysis and the yield reduction R-factor are discussed. Finally, in the framework of performance-based earthquake engineering, the assessment of demand and capacity is viewed through the lens of an IDA study. Copyright © 2001 John Wiley & Sons, Ltd.

3,334 citations


Journal ArticleDOI
TL;DR: In this paper, an improved pushover analysis procedure based on structural dynamics theory, which retains the conceptual simplicity and computational attractiveness of current procedures with invariant force distribution, is presented. But, the MPA procedure is not accurate enough for practical application in building evaluation and design.
Abstract: Developed herein is an improved pushover analysis procedure based on structural dynamics theory, which retains the conceptual simplicity and computational attractiveness of current procedures with invariant force distribution. In this modal pushover analysis (MPA), the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by a pushover analysis using the inertia force distribution for each mode. Combining these ‘modal’ demands due to the first two or three terms of the expansion provides an estimate of the total seismic demand on inelastic systems. When applied to elastic systems, the MPA procedure is shown to be equivalent to standard response spectrum analysis (RSA). When the peak inelastic response of a 9-storey steel building determined by the approximate MPA procedure is compared with rigorous non-linear response history analysis, it is demonstrated that MPA estimates the response of buildings responding well into the inelastic range to a similar degree of accuracy as RSA in estimating peak response of elastic systems. Thus, the MPA procedure is accurate enough for practical application in building evaluation and design. Copyright © 2001 John Wiley & Sons, Ltd.

1,130 citations


Journal ArticleDOI
TL;DR: In this article, a simplified linearized displacement-based procedure is presented along with recommendations for the selection of an appropriate substitute structure in order to provide the most representative analytical results for assessing the seismic resistance of brick masonry walls subject to out-of-plane bending.
Abstract: This paper addresses the problem of assessing the seismic resistance of brick masonry walls subject to out-of-plane bending. A simplified linearized displacement-based procedure is presented along with recommendations for the selection of an appropriate substitute structure in order to provide the most representative analytical results. A trilinear relationship is used to characterize the real nonlinear force–displacement relationship for unreinforced brick masonry walls. Predictions of the magnitude of support motion required to cause flexural failure of masonry walls using the linearized displacement-based procedure and quasi-static analysis procedures are compared with the results of experiments and non-linear time-history analyses. The displacement-based procedure is shown to give significantly better predictions than the force-based method. Copyright © 2002 John Wiley & Sons, Ltd.

298 citations


Journal ArticleDOI
TL;DR: In this paper, the optimal utilization of viscous and viscoelastic dampers in a structure to achieve a desired performance under earthquake-induced ground excitations is discussed. But the use of the genetic approach is not limited to any particular form of performance function as long as it can be calculated numerically.
Abstract: The effectiveness of viscous and viscoelastic dampers for seismic response reduction of structures is quite well known in the earthquake engineering community. This paper deals with the optimal utilization of these dampers in a structure to achieve a desired performance under earthquake-induced ground excitations. Frequency-dependent and -independent viscous dampers and viscoelastic dampers have been considered as the devices of choice. To determine the optimal size and location of these dampers in the structure, a genetic algorithm is used. The desired performance is defined in terms of several different forms of performance functions. The use of the genetic approach is not limited to any particular form of performance function as long as it can be calculated numerically. For illustration, numerical examples for different building structures are presented showing the distribution and size of different dampers required to achieve a desired level of reduction in the response or a performance index. Copyright © 2002 John Wiley & Sons, Ltd.

258 citations


Journal ArticleDOI
TL;DR: In this paper, the seismic response of single-degree-of-freedom (SDOF) systems incorporating flag-shaped hysteretic structural behavior, with self-centring capability, is investigated numerically.
Abstract: The seismic response of single-degree-of-freedom (SDOF) systems incorporating flag-shaped hysteretic structural behaviour, with self-centring capability, is investigated numerically. For a SDOF system with a given initial period and strength level, the flag-shaped hysteretic behaviour is fully defined by a post-yielding stiffness parameter and an energy-dissipation parameter. A comprehensive parametric study was conducted to determine the influence of these parameters on SDOF structural response, in terms of displacement ductility, absolute acceleration and absorbed energy. This parametric study was conducted using an ensemble of 20 historical earthquake records corresponding to ordinary ground motions having a probability of exceedence of 10% in 50 years, in California. The responses of the flag-shaped hysteretic SDOF systems are compared against the responses of similar bilinear elasto-plastic hysteretic SDOF systems. In this study the elasto-plastic hysteretic SDOF systems are assigned parameters representative of steel moment resisting frames (MRFs) with post-Northridge welded beam-to-column connections. In turn, the flag-shaped hysteretic SDOF systems are representative of steel MRFs with newly proposed post-tensioned energy-dissipating connections. Building structures with initial periods ranging from 0.1 to 2.0s and having various strength levels are considered. It is shown that a flag-shaped hysteretic SDOF system of equal or lesser strength can always be found to match or better the response of an elasto-plastic hysteretic SDOF system in terms of displacement ductility and without incurring any residual drift from the seismic event. Copyright © 2002 John Wiley & Sons, Ltd.

257 citations


Journal ArticleDOI
TL;DR: In this paper, six approximate methods to estimate the maximum inelastic displacement demand of single-degree-of-freedom (SFO) systems are evaluated, based on equivalent linearization.
Abstract: Six approximate methods to estimate the maximum inelastic displacement demand of single-degree-of-freedom systems are evaluated. In all methods, the maximum displacement demand of inelastic systems is estimated from the maximum displacement demand of linear elastic systems. Of the methods evaluated herein, four are based on equivalent linearization in which the maximum deformation is estimated as the maximum deformation of a linear elastic system with lower lateral stiffness and with higher damping coefficient than those of the inelastic system. In the other two methods the maximum inelastic displacement is estimated as a product of the maximum deformation of a linear elastic system with the same lateral stiffness and the same damping coefficient as those of the inelastic system for which the maximum displacement is being estimated, times a modifying factor. Elastoplastic and stiffness-degrading models with periods between 0.05 and 3.0 s are considered when subjected to 264 ground motions recorded on firm sites in California. Mean ratios of approximate to exact maximum displacements corresponding to each method are computed as a function of the period of vibration and as a function of the displacement ductility ratio. Finally, comments on the advantages and disadvantages of each method when applied to practical situations are given. Copyright © 2001 John Wiley & Sons, Ltd.

233 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a conceptual comprehensive numerical procedure for the performance-based seismic design of buildings and discuss the main requirements that a reliable PBSD should satisfy and why some approaches that have been proposed fail in satisfying those requirements, focusing on what is considered a promising probabilistic PBSD approach.
Abstract: The main objectives of this paper are: (i) to review briefly as to what is understood by performance-based engineering, performance-based seismic engineering, and performance-based seismic design (PBSD); (ii) to discuss the main requirements that a reliable PBSD should satisfy and why some approaches that have been proposed fail in satisfying those requirements; (iii) to focus on what is considered a promising probabilistic PBSD approach; and (iv) to present a conceptual comprehensive numerical procedure for the PBSD of buildings. It is shown that to satisfy the objectives of a reliable PBSD philosophy and procedure it is necessary to start with a multi-level seismic design criteria, to consider a probabilistic design approach, to consider local structural and non-structural damage and therefore design spectra for buildings (n degrees of freedom), to take into account the cumulative damage, and to control not only displacements but also ductility (minimum strength) to limit damage. Finally, it is concluded that a transparent and conceptual comprehensive preliminary design approach is necessary. Copyright © 2001 John Wiley & Sons, Ltd.

224 citations


Journal ArticleDOI
TL;DR: In this paper, a closed-form expression for estimating the fundamental vibration frequency of homogeneous triangular mountains is obtained, using Rayleigh's method, and numerical modelling based on the spectral element approximation is used to study the 3D seismic response of several real steep topographic irregularities excited by vertically propagating plane S-waves.
Abstract: The problem of amplification of seismic waves by surface topographic irregularities is addressed through analytical and numerical investigations. First, a closed-form expression for estimating the fundamental vibration frequency of homogeneous triangular mountains is obtained, using Rayleigh's method. Subsequently, numerical modelling based on the spectral element approximation is used to study the 3D seismic response of several real steep topographic irregularities excited by vertically propagating plane S-waves. A topographic amplification factor is obtained for each case, by a suitable average of the ratio of acceleration response spectra of output vs input motion. The 3D amplification factors are then compared with those derived by 2D analyses as well as with the topographic factors recommended in Eurocode 8 for seismic design. Copyright © 2002 John Wiley & Sons, Ltd.

210 citations


Journal ArticleDOI
TL;DR: In this paper, the distinct element method is used in order to predict the earthquake response of a multi-drum marble model of a classical column, and the results are compared with experimental data for an ‘identical’ specimen under the same excitation.
Abstract: In this paper, the distinct element method is used in order to predict the earthquake response of a multi-drum marble model of a classical column. The results are compared with experimental data for an ‘identical’ specimen under the same excitation. Both the numerical analysis and the experiments were conducted in three dimensions. The results show that the distinct element method can capture quite well the main features of the response, in spite of the sensitivity of the response to even small perturbations of the characteristics of the structure or the excitation. Attention, however, should be given to the appropriate values of the joint properties to be used. In any case, it seems that the method can be used with confidence in the restoration process of ancient monuments, in order to estimate the response to expected earthquake motions. Copyright © 2002 John Wiley & Sons, Ltd.

184 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical investigation into earthquake-induced floor horizontal accelerations that arise in regular buildings built with rigid diaphragms is presented, based on modal superposition modified to account for the inelastic response of the building's lateral force resisting system.
Abstract: Floor horizontal accelerations are needed for obtaining forces for the design of diaphragms, for the design of their connections and for the design of non-structural components and equipment supported by structures. Large floor horizontal accelerations have been recorded in buildings during earthquakes. Such accelerations have been responsible for inertia forces causing damage to services and are a major reason for structural damage and even building collapse. This paper describes an analytical investigation into earthquake-induced floor horizontal accelerations that arise in regular buildings built with rigid diaphragms. The paper also describes several methods prescribed by design standards and proposes a new method. The method is based on modal superposition modified to account for the inelastic response of the building's lateral force resisting system. Results obtained from time-history inelastic analysis are compared with the proposed method. Copyright © 2001 John Wiley & Sons, Ltd.

176 citations


Journal ArticleDOI
TL;DR: In this article, the structural response of SDF systems with a non-linear fluid viscous damper (FVD) was investigated and it was shown that structural deformation is reduced by up to 25% when ζsd = 5% and up to 60% when ǫ = 30%.
Abstract: The steady-forced and earthquake responses of SDF systems with a non-linear fluid viscous damper (FVD) are investigated. The energy dissipation capacity of the FVD is characterized by the supplemental damping ratio ζsd and its non-linearity by a parameter designated α. It is found that the structural response is most effectively investigated in terms of ζsd and α because (1) these two parameters are dimensionless and independent, and (2) the structural response varies linearly with the excitation intensity. Damper non-linearity has essentially no influence on the peak response of systems in the velocity-sensitive spectral region, but differences up to 14% were observed in the other spectral regions. The structural deformation is reduced by up to 25% when ζsd= 5%; and by up to 60% when ζsd= 30%. Non-linear FVDs are advantageous because they achieve essentially the same reduction in system responses but with a significantly reduced damper force. For practical applications, a procedure is presented to estimate the design values of structural deformation and forces for a system with non-linear FVD directly from the design spectrum. It is demonstrated that the earthquake-induced force in a non-linear FVD can be estimated from the damper force in a corresponding system with linear FVD, its peak deformation, and peak relative velocity; however, the relative velocity should not be approximated by the pseudo-velocity as this approximation introduces a large error in the damper force. Finally, a procedure is presented to determine the non-linear damper properties necessary to limit the structural deformation to some design value or the structural capacity for a given design spectrum. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a parametrical study of the pounding phenomenon associated with the seismic response of simply supported bridges with base isolation devices is carried out, focusing on the causal relationship between pounding and the properties of a spatially varying earthquake ground motion.
Abstract: This paper carries out a parametrical study of the pounding phenomenon associated with the seismic response of multi-span simply supported bridges with base isolation devices In particular, the analyses focus on the causal relationship between pounding and the properties of a spatially varying earthquake ground motion In order to include the effect of the torsional component of pounding forces on the seismic response of the whole structure, a three-dimensional (3D) finite element model has been defined and 3D non-linear time-history analyses have been performed A parametrical study on the size of the gaps between adjacent bridge decks has highlighted that the pounding effects are amplified when the spatially varying ground motion time histories at each support are considered Because of a spatially varying input, the pounding forces can assume values 3–4 times larger than those derived by a conventional seismic analysis with uniform input or with spatial input but considering ground motion wave passage effect only The numerical results show that in order to achieve an acceptably safe structural performance during seismic events, a correct design of the isolation devices should take into account the relative displacements calculated by means of a non-linear time-history analysis with multi-support excitation Copyright © 2002 John Wiley & Sons, Ltd

Journal ArticleDOI
TL;DR: In this article, a statistical method with combined uncertain frequency and mode shape data for structural damage identification is proposed, where the effects of uncertainties in both the measured vibration data and finite element model are considered as random variables in model updating.
Abstract: A statistical method with combined uncertain frequency and mode shape data for structural damage identification is proposed. By comparing the measured vibration data before damage or analytical finite element model of the intact structure with those measured after damage, the finite element model is updated so that its vibration characteristic changes are equal to the changes in the measured data as closely as possible. The effects of uncertainties in both the measured vibration data and finite element model are considered as random variables in model updating. The statistical variations of the updated finite element model are derived with perturbation method and Monte Carlo technique. The probabilities of damage existence in the structural members are then defined. The proposed method is applied to a laboratory tested steel cantilever beam and frame structure. The results show that all the damages are identified correctly with high probabilities of damage existence. Discussions are also made on the applicability of the method when no measurement data of intact structure are available. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a genetic algorithm is used to search for the optimum parameter values for the four dampers, installed in pairs along two orthogonal directions, for response control of torsional building systems subjected to bi-directional seismic inputs.
Abstract: This paper presents an approach for optimum design of tuned mass dampers for response control of torsional building systems subjected to bi-directional seismic inputs. Four dampers with fourteen distinct design parameters, installed in pairs along two orthogonal directions, are optimally designed. A genetic algorithm is used to search for the optimum parameter values for the four dampers. This approach is quite versatile as it can be used with different design criteria and definitions of seismic inputs. It usually provides a globally optimum solution. Several optimal design criteria, expressed in terms of performance functions that depend on the structural response, are used. Several sets of numerical results for a torsional system excited by random and response spectrum models of seismic inputs are presented to show the effectiveness of the optimum designs in reducing the system response. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, a study is conducted to search for the preferable MTMD which performs better and is easily manufactured from the five available models (i.e. MTMD-1 -MTMD-5), which comprise various combinations of the stiffness, mass, damping coefficient and damping ratio in the MTMD.
Abstract: Multiple tuned mass dampers (MTMD) consisting of many tuned mass dampers (TMDs) with a uniform distribution of natural frequencies are taken into consideration for attenuating undesirable vibration of a structure under the ground acceleration. A study is conducted to search for the preferable MTMD which performs better and is easily manufactured from the five available models (i.e. MTMD-1 -MTMD-5), which comprise various combinations of the stiffness, mass, damping coefficient and damping ratio in the MTMD. The major objective of the present study then is to evaluate and compare the control performance of these five models. The structure is represented by its mode-generalized system in the specific vibration mode being controlled by adopting the mode reduced-order approach. The optimum parameters of the MTMD-1 - MTMD-5 are investigated to reveal the influence of the important parameters on their effectiveness and robustness using a numerical searching technique. The parameters include the frequency spacing, average damping ratio, tuning frequency ratio, mass ratio and total number. The criteria selected for the optimum searching are the minimization of the maximum value of the displacement dynamic magnification factor (DDMF) and that of the acceleration dynamic magnification factor (ADMF) of the structure with the MTMD-1 - MTMD-5 (i.e. Min.Max.DDMF and Min.Max.ADMF). It is demonstrated that the optimum MTMD-1 and MTMD-4 yield approximately the same control performance, and offer higher effectiveness and robustness than the optimum MTMD-2, MTMD-3, and MTMD-5 in reducing the displacement and acceleration responses of structures. It is further demonstrated that for both the best effectiveness and robustness and the simplest manufacturing, it is preferable to select the optimum MTMD-1.

Journal ArticleDOI
TL;DR: In this article, a displacement-based design procedure for continuous concrete bridges is proposed which can be incorporated into a performance based design philosophy, and applied to the transverse response of bridge structures; however, it is equally well-suited for longitudinal response.
Abstract: A displacement-based design procedure for continuous concrete bridges is proposed which can be incorporated into a performance-based design philosophy. The procedure is applicable to multi-degree-of-freedom bridges with flexible or rigid superstructures, and for varying degrees of abutment restraint. The background and development of the design procedure is presented first, followed by a series of examples and validation studies using dynamic inelastic time-history analysis. The procedure is applied to the transverse response of bridge structures; however, it is equally well-suited for longitudinal response. The results indicate that the process is able to capture non-linear deformation patterns and thus reasonably control damage.

Journal ArticleDOI
TL;DR: In this paper, a marble model of a classical column of the Parthenon on the Acropolis of Athens was used to investigate the earthquake response of a 1:3 scale replica made from the same material as the original.
Abstract: Experimental results concerning the earthquake response of a marble model of a classical column are reported herein. The model was a 1:3 scale replica of a column of the Parthenon on the Acropolis of Athens, made from the same material as the original. Several earthquake motions, scaled appropriately in order to cause significant rocking but no collapse of the column, were used as the excitation. The base motion was applied in plane (in one horizontal and the vertical direction) or in space (in two horizontal and the vertical direction), using the shaking table facility at the Laboratory for Earthquake Engineering of the National Technical University of Athens. It was found that the column might undergo large deformations during the shaking, which are not necessarily reflected by the residual displacements at the end of it. For planar excitations, significant out-of-plane displacements can happen, triggered by the inevitable imperfections of the specimen. It was also verified that the response is very sensitive, even to small changes of the geometry or the input motion parameters. For this reason, the experiments were not repeatable and 'identical' experiments produced different results.

Journal ArticleDOI
TL;DR: In this article, an elementary stick model and a more sophisticated finite element formulation were employed to compute response quantities for highway overcrossing. But the results of the analysis were limited to the first six modes of interest and the validity of the proposed method was examined by comparing the computed time response quantities with records from the Meloland Road and Painter Street overcrossings located in southern and northern California, respectively.
Abstract: This paper presents a systematic procedure for the seismic response analysis of highway overcrossings. The study employs an elementary stick model and a more sophisticated finite element formulation to compute response quantities. All dynamic stiffnesses of approach embankments and pile groups are approximated with frequency-independent springs and dashpots that have been established elsewhere. A real eigenvalue analysis confirms the one-to-one correspondence between modal characteristics obtained with the three-dimensional finite element solutions and the result of the simpler stick-model idealization. A complex eigenvalue analysis yields modal damping values in the first six modes of interest and shows that modal damping ratios assume values much higher than those used by Caltrans. The validity of the proposed method is examined by comparing the computed time response quantities with records from the Meloland Road and Painter Street overcrossings located in southern and northern California, respectively. The proposed procedure allows for inexpensive parametric analysis that examines the importance of considering soil–structure interaction at the end abutments and centre bent. Results and recommendations presented by past investigations are revisited and integrated in comprehensive tables that improve our understanding of the dynamic characteristics and behaviour of freeway overcrossings. The study concludes with a step-by-step methodology that allows for a simple, yet dependable dynamic analysis of freeway overcrossings, that involves a stick model and frequency-independent springs and dashpots. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the body is sensitive to small changes in the friction coefficient and slenderness, and to the wave properties and intensity of ground motions, and it is concluded that governing equations of motion and boundary conditions in view of discontinuous nonlinear systems are necessary to analyse actual motions of the rectangular rigid bodies subjected to horizontal and vertical ground motion.
Abstract: This investigation deals with non-linear seismic responses of free-standing rectangular rigid bodies on horizontally and vertically accelerating rigid foundations. The responses are classified into two initial responses and four subsequent responses, accordingly the equations of motion governing the liftoff, slip and liftoff–slip interaction motions and boundary conditions corresponding to commencement and termination of the motions are defined. The time histories of responses presented herein show that the body is sensitive to small changes in the friction coefficient and slenderness, and to the wave properties and intensity of ground motions. Systematic trends are observed: the bodies on the low-grip foundation avoid overturning while they are allowed to slip regardless of details of ground motions; the long period earthquakes tend to make the body overturn and slip largely. In contrast, the timing when liftoff and slip commences and terminates and their directions do not directly correspond with intensity of ground motions. Moreover, the vertical ground motion adds irregularities on the responses, since it excites or damps the responses. It is concluded that governing equations of motion and boundary conditions in view of discontinuous non-linear systems are necessary to analyse actual motions of the rectangular rigid bodies subjected to horizontal and vertical ground motion. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, a 3D model that is practically suitable to precisely analyse pounding between bridge girders is presented, and experiments have been conducted to verify the proposed pounding model.
Abstract: Unseating of bridge girders/decks during earthquakes is very harmful to the safety and serviceability of bridges. Evidence from recent severe earthquakes indicates that in addition to damage along longitudinal direction, lateral displacement and rotation of bridge girders caused by pounding to adjacent girders can also lead to unseating. To simulate this effect, 3D modelling of the dynamic performance of whole bridge structures, including pounding, is needed strongly. This paper presents a 3D model that is practically suitable to precisely analyse pounding between bridge girders. Experiments have been conducted to verify the proposed pounding model. The 3D non-linear modelling of steel elevated bridges is also discussed. A general-purpose dynamic analysis program for bridges, namely dynamic analysis of bridge systems (DABS) has been developed. Seismic analyses on a chosen three-span steel bridge are conducted for several cases including pounding as a case study. The applicability of the proposed pounding model is illustrated by the computations. The effects of poundings on the response of bridge girders are discussed and the computation results are given. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: Based on the approximation by polynomial-fraction, a series of systematic lumped-parameter models are developed in this article for efficiently representing the dynamic behaviour of unbounded soil.
Abstract: Based on the approximation by polynomial-fraction, a series of systematic lumped-parameter models are developed in this paper for efficiently representing the dynamic behaviour of unbounded soil. Concise formulation is first employed to represent the dynamic flexibility function of foundation with a ratio of two polynomials. By defining an appropriate quadratic error function, the optimal coefficients of the polynomials can be directly solved from a system of linear equations. Through performing partial-fraction expansion on this polynomial-fraction and designing two basic discrete-element models corresponding to the partial fractions, systematic lumped-parameter models can be conveniently established by connecting these basic units in series. Since the systematic lumped-parameter models are configured without introducing any mass, the foundation input motion can be directly applied to these models for their applications to the analysis of seismic excitation. The effectiveness of these new models is strictly validated by successfully simulating a semi-infinite bar on an elastic foundation. Subsequently, these models are applied for representing the dynamic stiffness functions for different types of foundation. Comparison of the new models with the other existing lumped-parameter models is also made to illustrate their advantages in requiring fewer parameters and featuring a more systematic expansion. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, three identification algorithms are developed to estimate the control parameters of hysteresis for different classes of inelastic structures, based upon the simplex, extended Kalman filter, and generalized reduced gradient methods.
Abstract: The generalized model of differential hysteresis contains 13 control parameters with which it can curvefit practically any hysteretic trace. Three identification algorithms are developed to estimate the control parameters of hysteresis for different classes of inelastic structures. These algorithms are based upon the simplex, extended Kalman filter, and generalized reduced gradient methods. Novel techniques such as global search and internal constraints are incorporated to facilitate convergence and stability. Effectiveness of the devised algorithms is demonstrated through simulations of two inelastic systems with both pinching and degradation characteristics in their hysteretic traces. Owing to very modest computing requirements, these identification algorithms may become acceptable as a design tool for mapping the hysteretic traces of inelastic structures.

Journal ArticleDOI
TL;DR: In this article, the authors proposed energy input spectra applicable to seismic design of structures located in low-to-moderate-seismicity regions, which represent the load effect, in terms of input energy, of the most severe earthquake that the construction might encounter during its lifetime.
Abstract: This paper proposes energy input spectra applicable to seismic design of structures located in low-to-moderate-seismicity regions. These spectra represent the load effect, in terms of input energy, of the most severe earthquake that the construction might encounter during its lifetime. The spectra have been derived through dynamic response analyses of over 100 ground motion records obtained from 48 earthquakes that have occurred in Spain. An empirical equation for estimating the energy input contributable to damage from the total input energy is also suggested. This equation takes into account both the damping and the degree of plastification of the structure. Finally, the proposed design energy input spectra are compared with the provisions of the current Spanish Seismic Code and with the response spectra of recent earthquakes that have occurred in Turkey and Taiwan. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the authors compared approximate analytical solutions and finite element results to conclude on a simple procedure that allows for the estimation of the kinematic response functions and dynamic stiffnesses of approach embankments.
Abstract: Recognizing that soil-structure interaction affects appreciably the earthquake response of highway overcrossings, this paper compares approximate analytical solutions and finite element results to conclude on a simple procedure that allows for the estimation of the kinematic response functions and dynamic stiffnesses of approach embankments. It is shown that the shear-wedge model yields realistic estimates for the amplification functions of typical embankments and reveals the appropriate levels of dynamic strains which are subsequently used to estimate the stiffness and damping coefficients of embankments. The shear-wedge model is extended to a two-dimensional model in order to calculate the transverse static stiffness of an approach embankment loaded at one end. The formulation leads to a sound closed-form expression for the critical length, , that is the ratio of the transverse static stiffness of an approach embankment and the transverse static stiffness of a unit-width wedge. It is shown through two case studies that the transverse dynamic stiffness (“spring” and “dashpot”) of the approach embankment can be estimated with confidence by multiplying the dynamic stiffness of the unit-width wedge with the critical length, . The paper concludes that the values obtained for the transverse kinematic response function and dynamic stiffness can also be used with confidence to represent the longitudinal kinematic response function and dynamic stiffness respectively.

Journal ArticleDOI
Jie Li1, Jun He1
TL;DR: In this article, a new probabilistic analytical approach to evaluate seismic system reliability of large lifeline systems is presented, which takes the shortest path from the source to the terminal of a node weight or edge weight network as decomposition policy.
Abstract: A new probabilistic analytical approach to evaluate seismic system reliability of large lifeline systems is presented in this paper. The algorithm takes the shortest path from the source to the terminal of a node weight or edge weight network as decomposition policy, using the Boolean laws of set operation and probabilistic operation principal, a recursive decomposition process then could be constructed. For a general weight network, the modified Torrieri method (NTR/T method) is introduced to combine with the suggested algorithm. Therefore, the recursive decomposition algorithm may be applied to evaluate the seismic reliability of general lifeline systems. A series of case studies, including a practical district electric power network system and a large urban water supply system, show that the suggested algorithm supplies a useful probabilistic analysis means for the seismic reliability evaluation of large lifeline systems. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, an analytical model for high damping elastomeric isolation bearings is presented, which is used to describe mathematically the damping force and restoring force of the rubber material and bearing.
Abstract: An analytical model for high damping elastomeric isolation bearings is presented in this paper. The model is used to describe mathematically the damping force and restoring force of the rubber material and bearing. Ten parameters to be identified from cyclic loading tests are included in the model. The sensitivity of the ten parameters in affecting the model is examined. These ten parameters are functions of a number of influence factors on the elastomer such as the rubber compound, Mullins effect, scragging effect, frequency, temperature and axial load. In this study, however, only the Mullins effect, scragging effect, frequency and temperature are investigated. Both material tests and shaking table tests were performed to validate the proposed model. Based on the comparison between the experimental and the analytical results, it is found that the proposed analytical model is capable of predicting the shear force–displacement hysteresis very accurately for both rubber material and bearing under cyclic loading reversals. The seismic response time histories of the bearing can also be captured, using the proposed analytical model, with a practically acceptable precision. Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
Abstract: The objective of this study is to investigate the effect of masonry infills on the seismic performance of low-rise reinforced concrete (RC) frames with non-seismic detailing. For this purpose, a 2-bay 3-storey masonry-infilled RC frame was selected and a 1 : 5 scale model was constructed according to the Korean practice of non-seismic detailing and the similitude law. Then, a series of earthquake simulation tests and a pushover test were performed on this model. When the results of these tests are compared with those in the case of the bare frame, it can be recognized that the masonry infills contribute to the large increase in the stiffness and strength of the global structure whereas they also accompany the increase of earthquake inertia forces. The failure mode of the masonry-infilled frame was that of shear failure due to the bed-joint sliding of the masonry infills while that of the bare frame appeared to be the soft-storey plastic mechanism at the first storey. However, it is judged that the masonry infills can be beneficial to the seismic performance of the structure since the amount of the increase in strength appears to be greater than that in the induced earthquake inertia forces while the deformation capacity of the global structure remains almost the same regardless of the presence of the masonry infills. Copyright © 2001 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the results of pseudo-dynamic tests for the development of a mathematical model of a three-storey reinforced concrete frame building with masonry infill in the bottom two storeys were used.
Abstract: In this paper, a technique is presented which employs the results of pseudo-dynamic tests for the development of a mathematical model. This technique, described by means of the mathematical modelling of a three-storey reinforced concrete frame building with infill in the bottom two storeys, which was tested at ELSA in Ispra, proved to be effective and to lead to a fairly accurate structural model. The results of analyses suggest that the global non-linear seismic response of reinforced concrete frames with masonry infill can be adequately simulated by a relatively simple mathematical model, which combines beam elements with concentrated plasticity, simple connection elements, and equivalent strut elements representing the infill walls (provided that the infill does not fail out of plane and that no shear sliding failure occurs). Copyright © 2002 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the governing equations for dynamic transverse motion of a cable-stayed beam are obtained by means of a classical variational formulation, which permits a parametric investigation of linear and non-linear behaviour in a family of cable-stood beam systems.
Abstract: The governing equations for dynamic transverse motion of a cable-stayed beam are obtained by means of a classical variational formulation. The analytical model permits a parametric investigation of linear and non-linear behaviour in a family of cable-stayed beam systems. Analytical eigensolutions of the linearized equations are used to investigate how the mechanical characteristics influence the occurrence of global, local and coupled modes. The exact eigenfunctions are assumed to describe the forced harmonic motion in the neighbourhood of a selected frequency. The frequency–amplitude relationship, obtained by the use of the multiple scale method, permits the description of softening and hardening behaviour in the global, local and coupled classes of motion. Copyright © 2002 John Wiley & Sons, Ltd

Journal ArticleDOI
TL;DR: In this paper, a Monte Carlo simulation approach is followed in conjunction with advanced finite element procedures to determine the risk of damage to the soil-structure system due to liquefaction under a wide range of earthquake intensities.
Abstract: The present study deals with the non-linear stochastic dynamic analysis of a soil-structure interacting system. The ultimate objective is to determine the risk of damage to the system due to liquefaction under a wide range of earthquake intensities. A Monte Carlo simulation approach is followed in conjunction with advanced finite element procedures. The stochastic spatial variability of soil properties and the randomness of the seismic excitation are taken into account in order to estimate the statistics of the response, measured in terms of uniform foundation settlement and tilting. Specifically, soil properties are modelled as non-Gaussian random fields and seismic excitations as non-stationary random processes. The probabilistic characteristics of the stochastic field modelling soil properties are established from in situ tests. The risk of damage to the soil-structure system due to liquefaction is assessed by establishing fragility curves, which are of paramount importance for risk assessment and management studies of such systems. Fragility curves express the probability of exceeding various thresholds in the response. The relative effect of the variability of various soil parameters on the variability of the response is also examined. Copyright (C) 2002 John Wiley Sons, Ltd.