Earthquake Response Analysis Research Articles

Characteristics of Local Site Effects on Seismic Motion. Non-linearity of Soil and Geological Irregularity.

To determine seismic ground motion for aseismic design, it is necessary to take site effects into account, such as non-linearity of soil and geological irregularities. In this paper, we discuss two aspects of site effects. One is the estimation of nonlinear earthquake response of soil deposits, and the other the estimation of seismic motion on the ground that has topographical and geological irregularities. We propose a new stress-strain model that is applicable to earthquake response analyses of soil deposits under large earthquakes. Next, we develop a practical method to evaluate amplification characteristics of ground motion on the irregularly layered ground.

鋼構造強柱偏心立体骨組におけるエネルギー消費部材の必要塑性変形能力 : 1層1スパン耐力偏心骨組

When a steel space frame with eccentricity is subjected to horizontal force due to earthquake, torsional vibration is developed and plastic deformation is concentrated in the outer plane frame. Many studies to investigate the effect of eccentricity on earthquake response of space frames has been carried out. In this paper, the effect of the structural parameters and input earthquake direction on plastic deformation capacity demand of strong column type steel space frame members is solved theoretically. The analytical model is one story - one bay rectangular plane type frame, whose each plane frame's strength and rigidity are proportional. The relation between load and deformation of space frame against any input earthquake direction can lead the formula to estimate plastic deformation capacity demand of members. The results of earthquake response analysis agree well with the theoretical prediction.

Correlation of damage and analysis of R/C building: Experience from the 1995 Kobe earthquake

During the 1995 Hyogoken-Nanbu Earthquake, a reinforced concrete building, called Jeunesse Rokko, suffered intermediate damage by forming a beam-yielding (weak-beam strong-column) mechanism, which has been regarded as the most desirable earthquake resisting mechanism throughout the world. High cost to repair damage at many beam ends and poor appearance expected after the repair work made the owner decide to tear down the building. Nonlinear earthquake response analyses were conducted to simulate the behavior of the building during the earthquake. The influence of non-structural members was considered in the analysis. The calculated results were compared with the observed damage, especially the location of yield hinges and compression failure of spandrel beams, and the degree of cracking in columns and in column-girder connections.

複合基礎の地震応答解析法に関する実証的研究

Dynamic characteristics of a composite foundation of wall and pile group are investigated using the results of forced vibration test and earthquake observation. It is clarified that the interior piles show similar vibration mode to that of the wall foundation, and the existence of basement and interior piles restrict the natural vibration of the interior soil. The analytical results using an axisymmetric FEM show the shear force during earthquake is largely burdened by the wall foundation and that is large at the deep part of the soil. The effectiveness of the simplified lumped-mass model is verified through earthquake response analyses.

Nonlinear Behavior of Surface Deposit during the 1995 Hyogoken-Nambu Earthquake

ABSTRACT Behavior of the ground during the 1995 Hyogoken-Nambu earthquake is investigated through various analyses on and comparisons with the earthquake records. Behavior of the Holocene clay, a soft clay layer, as well as the fill, the liquefied layer, is shown to affect the response of the ground significantly through effective stress analysis. Earthquake response analysis carried out on the section passing the Sannomiya station indicates that the existence of the Holocene clay and its thickness controls the response of the ground surface to a great degree. It is also shown that there was no deamplification effect caused by the non-linear behavior of the soil in the area called the damage belt, where damage to houses was especially severe. Incident waves on the top of the upper Osaka Group formation are estimated for several sites where earthquake records were obtained by deconvolution analysis. Their waveforms on the base layer are very similar to each other in a narrow region a few kilometers wide, but are different from those at distant sites, although their PGV are nearly the same at about 80 cm/s. It is shown that the ground shaking observed at the 1995 Hyogoken-Nambu earthquake was characterized mainly by the surface geology, and that it was are controlled by the nonlinear behavior of the soft clay layer and liquefaction of fill.

Poly-linear型履歴ダンパーを用いた多層構造物の最適地震応答制御について

This paper presents an analytical approach to the optimality of ploy-linear type hysteretic damper useful for near-field ground motions such as the Hyogo-ken Nanbu(1995) earthquake on the basis of seismic random earthquake response analysis. Numerical calculations are carried out for six-degree-of-freedom structural systems with the damper. From two viewpoints of preservation of structural seismic safety and improvement of structural amenity, the optimum parameters of the damper are determined in such a way that the structural systems suffer no damage under medium or strong earthquake excitations, while the systems suffer only minor recoverable damage under severe or catastrophic earthquake excitations. The applicability of the optimum poly-linear type hysteretic damper based on the stationary non-white random process is demonstrated through the simulation analysis using the recorded earthquake accelerogram during the Hyogo-ken Nanbu earthquake.

Non-linear seismic cracking analysis of medium-height concrete gravity dams

The non-linear dynamic response of concrete gravity dams under seismic loads is a little-understood phenomenon due to limitations in the previous studies. The choice of a reliable concrete constitutive model and constitutive parameters to predict the performance of concrete gravity dams under severe earthquake ground motion is one of the most complex tasks. The response of a typical medium-height concrete gravity dam to a realistic motion is examined using the ADINA concrete model. The fracture energy cracking criterion is applied to remove the unreasonable mesh sensitivity of the results. The influence of the constitutive parameters on the earthquake response analysis of concrete gravity dams is also discussed.

Vibration Tests on a Full-Size Suspen-Dome Structure

A “suspen-dome” structural system consisting of a thin-walled dome and a tensegric system is described, and an overview and results of vibration tests on a full-sized structure are given. The tests revealed the vibration characteristics of the suspen-dome. Close agreement between analytical results based on design information and the test results confirms that the design method used is appropriate. Effectiveness of the suspen-dome against earthquake motions, particularly vertical motions, was confirmed through elastic earthquake response analysis.

Study of Dynamic Collapse of Single Layer Reticular Domes Subjected to Earthquake Motion and the Estimation of Statically Equivalent Seismic Forces

The present paper investigates the dynamic response characteristics of single layer reticular domes subjected to horizontal earthquake motions from the following view points: (1) how to estimate the statically equivalent seismic forces applied to domes both for high rise and low rise; and (2) how to estimate the collapse accelerations under which the domes collapse dynamically. For these purposes, linear response analyses, linear buckling analyses, geometrically and materially nonlinear static analyses and geometrically and materially nonlinear earthquake response analyses are performed. Based on the results, the collapse accelerations are expressed as a function of the safety factor for domes under self weight. The expression for the collapse accelerations leads to an approximate measure by which structural designers may balance the static resistant capacity under self weight and the dynamic resistant capacity under earthquake motions.

Interpretation of Large-Strain Seismic Cross-Hole Tests

At sites in earthquake-prone areas, a reliable expression of the nonlinear dynamic stress-strain behavior of soil for the different depths of interest is needed for earthquake-response analyses. Most currently used geophysical seismic tests generate only small amplitude waves, which are in the linear stress-strain range, and the nonlinear behavior is inferred from laboratory tests. A seismic cross-hole test has been developed in which large dynamic forces are applied at different depths in a borehole. Velocity sensors located in three additional boreholes at various distances from the source hole measures the particle velocity and the time it takes the shear wave generated at the source borehole to travel horizontally to each of the receiver boreholes. The generated shear strains are well into the nonlinear stress-strain range. This paper provides a systematic interpretation scheme for the data from these large-strain geophysical crosshole tests. Use is made of both the measured particle velocities at each sensor and the travel times to each borehole to develop modulus degradation curves. The interpretation procedure is applied to a well-documented case study.

Soil-structure interaction analysis of the Hualien containment model

This paper presents results from forced vibration tests, microtremor observations and earthquake response analysis of a nuclear reactor containment model constructed on stiff soil in Hualien, Taiwan. The dynamic behavior of the soil-structure system is simulated successfully with two numerical models: a sway-rocking model, whose soil parameters are evaluated on the basis of the continuum formulation method, and a finite element model, using the program SASSI with the flexible volume substructuring approach. The dependences of the soil parameters of both models on the amplitudes of the different dynamic excitations are investigated in detail. An original numerical simulation of microtremor is performed. Comparison with results of a previous study involving a rigid tower on a soft soil site in Chiba, Japan is offered.

Application of Object-Oriented Approach to Earthquake Engineering

A variety of computer programs has been developed in order to analyze complicated structures. As the number of functions in their programs increase, it becomes difficult to manage them. The fundamental problem lies in the fact that they are designed in a computer-oriented manner which is totally different from our intuition. Therefore the object-oriented approach is efficient to overcome the above mentioned problems. In this study, the three-module model for the structural analysis system is proposed. The system is characterized by the structure, load and analysis modules passing messages each other. This model is more flexible and more useful than the conventionally used structure-based model for the earthquake response analysis problem as well as the structure analysis problem. Recently, Object-Oriented technique (OO) has be- come popular and it's advantage is being recognized in many field. Some researchers are applying the OO ap- proach to the structural analysis field and a great deal of effort has been made on its application to the finite element method 1) 2)3)4) . In their articles, the OO tech- nique was only applied to the structure and the other objects were not modeled positively. In earthquake engineering, an earthquake is not only a load. It is an objective of our seismic design, so we would better focus on it in the system. And since we use many method besides the FEM, it is desirable to be able to select a proper method to an objective model. In this paper, we propose a flexible object-oriented analytical system based on modules. Firstly, we sum- marize the problem domain of the earthquake engineer- ing system and pick up some important items. Secondly, the detailed analysis of each item is described. Finally, through the implementation of the models, we explain the benefits of this approach and the reusage of objects.

A simplified effective stress method of soil mass earthquake response analysis (in Chinese): Chen Guoxing, Xie Junfei, Han Wei & Zhang Kexu, Earthquake Engineering & Engineering Vibration, 15(2), 1995, pp 52–61

A simplified effective stress method of soil mass earthquake response analysis (in Chinese): Chen Guoxing, Xie Junfei, Han Wei & Zhang Kexu, Earthquake Engineering & Engineering Vibration, 15(2), 1995, pp 52–61

Earthquake response analysis of soil-pile-nuclear power station auxiliary workshop structure interaction system (in Chinese): Ying Jianian, Wang Rongchang & Yu Zaidoao, Earthquake Engineering & Engineering Vibration, 15(1), 1995, pp 44–52

Earthquake response analysis of soil-pile-nuclear power station auxiliary workshop structure interaction system (in Chinese): Ying Jianian, Wang Rongchang & Yu Zaidoao, Earthquake Engineering & Engineering Vibration, 15(1), 1995, pp 44–52

Role of viscous damping in nonlinear vibration of buildings exposed to intense ground motion

Abstract It is the purpose of this paper to present how important the role of viscous damping is in preventing buildings from story collapse during intense earthquake ground motion. The paper first covers an earthquake response analysis of a single-degree-of-freedom model with various types of damping. The study shows that only the viscous damping can decrease the displacement of the model subject to large plastic deformation. Then, with the use of some ten-degree-of-freedom shear models, it is found that the viscous damping is capable of making up for a deficient strength of any story of a building, preventing the structural damage from concentrating into that story. Finally, installation of visco-elastic dampers into RC buildings is found to be a better means of improving their ultimate seismic stability than other conventional means of seismic strengthening.

Seismic Wave Propagation in Elastic Soil With Continuous Variation of Shear Modulus in the Vertical Direction

A conventional type of earthquake response analysis of ground gave a maximum acceleration for soft deposits that is lower than that for stiffer soil conditions. Since this was contradictory against the knowledge that soft deposits are more hazardous, an improvement of the analysis was attempted. A series of geophysical surveys was carried out to investigate the variation of shear wave velocity in the vertical direction and it was suggested that the velocity and shear modulus vary more continuously with depth even though the soil type changes from cohesive to cohesionless. The idea of continuity in soil property was further supported by the variation of fines content with depth. With these in mind, a wave propagation equation was developed and then solved analytically by taking into account the continuity of modulus. The calculated amplification of seismic motion indicated that more wave energy can reach the ground surface with this new analysis than in the more conventional way of calculation.

接合部パネルの変形を考慮した角形鋼管柱・H形鋼梁ラーメン構造の地震応答解析

This paper describes the results of earthquake response analysis of rigid frames with RHS columns allowing for deformation of joint panels. The major objective of this analysis is to investigate the inelastic response of member in the frames under strong earthquake ground motions. From the results of the response analysis, maximum story deformation anale of the frames and cumulative plastic deformation of members can be obtained. The effect of energy absorption by joint panels and the influence of vertical earthquake around motions are also discussed in this paper.

Earthquake analysis of arch dams including dam‐water‐foundation rock interaction

AbstractThe available substructure method and computer program for the earthquake response analysis of arch dams, including the effects of dam‐water interaction, reservoir boundary absorption, and foundation rock flexibility, is extended to include the effects of dam‐foundation rock interaction with inertia and damping of the foundation rock considered. Efficient techniques are developed for evaluating the foundation impedance terms, computationally the most demanding part of the procedure.

大スパン構造物の弾塑性振動特性に関する基礎的研究 : 定常振動解に基づく偏平三角ラーメンの振動性状の考察

Dynamic elasto-plastic behavior of long span structures has been investigated by performing time-domain earthquake response analysis. However, such a numerical simulation is not suitable to examine thoroughly the overall. characteristics of the obtained solution related to various parameters. The purpose of this paper is to discuss the nonlinear dynamics of the long span structures with geometrical and material nonlinearities based on the frequency-domain periodic solution. In this approach, we obtain the resonance curves, which are closely related with the resistant capacity against dynamic load, by applying equivalent linearization technique and harmonic balance method. The elasto-plastic shallow triangular frame, which is originally the example of the so-called Williams' toggle frame, was analyzed in order to examine the typical characteristics of the long span structures. As a result, the significant properties of the elastoplastic vibration were revealed clearly in the form of the resonance curves.

Discussion on a paper by X. N. Duan and A. M. Chandler

AbstractThe authors have presented the results of inelastic earthquake response analysis of a class of asymmetric building models and concluded that regularly asymmetric buildings excited well into the inelastic range may not be conservatively designed via modal analysis of their elastic models. The purpose of this short communication is to refer to the results in contrast to the authors' and to make some comments on their paper.