Characteristics Of Earthquake Motions Research Articles

Effects of Vertical Motion on Uplift of Underground Structure Induced by Soil Liquefaction

The uplift of underground structures induced by soil liquefaction can damage underground structure systems. Numerical simulations have shown that uplift is positively correlated with the energy of horizontal input motion. However, the effects of vertical input motion on uplift have not been studied comprehensively in the past. Previous studies on the vertical motion concluded that the effects of vertical motion on uplift depend on the overall characteristics of earthquake motion. These motion characteristics have only been studied separately in previous studies. A comprehensive study to explore the interactions and overall effects of these characteristics on the uplift of underground structures is essential. In this study, the FLAC program with the PM4Sand model was used as a numerical tool to explore the effects of vertical input motion on the uplift of underground structures. The numerical model was calibrated using centrifuge test results, and 48 earthquake motions were selected as input motions to study the effects of the overall characteristics of earthquake motions on the uplift of underground structures. The simulation results show that the frequency content characteristics of horizontal and vertical motion are the major factors affecting the uplift magnitude and the responses of liquefiable soils. However, most simulation cases show that the inclusion of vertical motion causes a 10% difference in the tunnel uplift, compared to cases without vertical motion.

Performance-based-plastic-design of damage-control steel MRFs equipped with self-centring energy dissipation bays

Driven by the demand of producing novel seismic resilient structures, this study focused on steel moment resisting frames equipped with superelastic shape memory alloy (SMA) connections in the self-centring energy dissipation bays, and the emphasis was given to a direct-iterative design method for performance-based-plastic-design of the system under earthquake motions. Utilising the equivalent single-degree-of-freedom (SDF) oscillator which may reasonably quantify the dynamic responses of a multi-storey structure, an inelastic structural seismic demand model motivated by nonlinear spectral analyses was developed, and the statistic features were accounted. As the theoretical basis of the design philosophy, the seismic energy equilibrium equation of the structure was correlated with structural arrangement and earthquake motion characteristics. Then, a stepwise plastic design methodology enabling practising engineers to search for a feasible design strategy was proposed. Three prototype structures were developed following the proposed method, and finite element models of the systems were developed. The adequacy of the modelling techniques was verified by the test database, and the sufficiency of the hysteretic model of the structure was also justified. The seismic responses of the prototype structures were estimated by nonlinear static and dynamic analyses. The analysis data pool confirmed that the prototype structures were able to achieve the damage-control objective by limiting the maximum interstorey drifts below the prescribed deformation threshold, and inelastic actions were concentrated in the self-centring energy dissipation bays.

Seismic performance of high‐rise building with a rock‐slip isolation system with cables

SUMMARYTo avoid the overturning hazard of high‐rise buildings with traditional isolation technology, a rock‐slip structure with cables (RSSC) was proposed to improve their seismic performance. The mechanical model was established, and the motion behaviour equation of the RSSC was derived. Shake‐table tests of the RSSC were performed, and the results were compared with the corresponding finite‐element model simulations. The influences of key structural parameters and earthquake motion characteristics were analysed. The study results showed that the RSSC could effectively reduce the internal seismic force response and interlayer deformation under a severe earthquake, as well as decrease the overturning probability. The seismic reduction effect was influenced by the prestressed force, the aspect ratio of the structure, and the friction coefficient between the superstructure and foundation as well as seismic site type. The motion equation derived in this paper can be used to theoretically predict the motion behaviour of RSSC.

Fragility Assessment Model of Building Structures Using Characteristics of Artificial Aftershock Motions

AbstractAny additional loads applied to a damaged structure can aggravate its instability and thus, the impact of successive earthquakes need to be considered. This study proposed a quantitative assessment model for the fragility of a damaged structure subjected to aftershock. Mean period and the strong motion duration were considered as characteristics of earthquake motions. Simulation models of two reinforced concrete structures and one steel structure were selected to examine the applicability of the model. Based on the suggested fragility and residual deformation coefficients, critical earthquake sequences for each structure were identified. The proposed model was efficient in selecting critical earthquake sequences by using the limited number of aftershocks, and these sequences are expected to be useful indicators in the establishment of a retrofit plan according to the predicted structural response and target performance levels.

KL展開による地震動の経時特性のモード分解と合成

地震動の経時特性を表す特徴量として，正規化加速度累積パワー曲線 (Husid plot) に基づく98次元の特徴ベクトルが能島ら(2017)により提案されている．本研究ではこの98次元の特徴ベクトルにKL (Karhunen-Loéve) 展開を適用し，経時特性のモード分解とモード合成による近似方法を提案するものである．特徴ベクトルの分散共分散行列の固有値解析により固有値と固有ベクトルを求める．その直交行列を用いて特徴ベクトルを主成分に変換するとともに，主要モードからなる部分空間における逆変換により特徴ベクトルを近似し，情報損失の少ない次元縮約を図るものである．再合成された包絡形状の適合性の検証にはカーネル密度推定を用いる．2011年東北地方太平洋沖地震の691観測記録を対象とした適用例を示した．KL展開による正規直交基底を用いれば，3～6次元程度の部分空間で経時特性を概ね表現可能であることが明らかとなった．ただし振幅特性の変動が複雑な波形に対しては，より高次の情報を要する場合もあることもわかった．

地震動の経時特性の特徴抽出と階層的クラスター分析による分類

地震動の経時特性を表す特徴量として, 正規化加速度累積パワー曲線 (Husid plot) に基づく98次元の特徴ベクトルを提案した．また特徴ベクトル間のユークリッド距離によって波形間の非類似度を定義し, 階層的クラスター分析によって経時特性を分類する手法を提案した．2011年東北地方太平洋沖地震の観測記録に適用してクラスター分類結果をマップ化し, 多重震源過程や震源域からの距離の影響を受けた経時特性を的確に分類可能であることを明らかにした．また計量的多次元尺度法によって波形を二次元布置し, 経時特性の分類の意味を明らかにした．さらにSR継続時間の分布を示し, クラスター分類結果はSR継続時間のみでは表せない経時特性を反映していることを指摘した．

地震動特性と地盤の非線形応答特性を考慮した地中せん断応力の評価方法

地震動特性と地盤の非線形応答特性を考慮した地中せん断応力の評価方法

Effects of Characteristics of Earthquake Motion on Elastic-Plastic Seismic Response of Single-Degree-of-Freedom

320 strong motion records of four sites are appropriately selected. The elasto-plastic dynamic analysis program is used to research the effects of characteristics of earthquake motion on elasto-plastic acceleration spectra, elasto-plastic displacement spectra, residual displacement spectra and reduced strength spectra. The study results are obtained as follow: 1) The value of elasto-plastic acceleration spectra, elasto-plastic displacement spectra, residual displacement spectra are increased with the amplification of seismic magnitude. 2) When site soil softens, the elasto-plastic acceleration, displacement, residual displacement of the same period are amplified in site Ⅲ and Ⅳ. On the contrary, site conditions of site Ⅲ and Ⅳ have nothing to do with elasto-plastic response spectra. 3) When ductility is greater than two, reduced strength spectra can be affected by seismic magnitude and site conditions. 4) Elasto-plastic response spectra of other protected earthquake intensity can be obtained by adjusting elasto-plastic response spectra of the standard protected earthquake intensity according to the ratio of PGA (protected earthquake intensity) to PGA (standard protected earthquake). So, some meaningful references are provided for performance-based seismic design for bridge.

Effects of soil–foundation–structure interaction on seismic structural response via robust Monte Carlo simulation

Uncertainties involved in the characterization and seismic response of soil–foundation–structure systems along with the inherent randomness of the earthquake ground motion result in very complex (and often controversial) effects of soil–foundation–structure interaction (SFSI) on the seismic response of structures. Conventionally, SFSI effects have been considered beneficial (reducing the structural response), however, recent evidence from strong earthquakes has highlighted the possibility of detrimental effects or increase in the structural response due to SFSI. This paper investigates the effects of SFSI on seismic response of structures through a robust Monte Carlo simulation using a wide range of realistic SFS systems and earthquake input motions in time-history analyses. The results from a total of 1.36 million analyses are used to rigorously quantify the SFSI effects on structural distortion and total horizontal displacement of the structure, and to identify conditions (system properties and earthquake motion characteristics) under which SFSI increases the structural response.

Semi-Active Control for Base Isolated Structure Using Response Evaluator Subjected to Long-Period Earthquake Ground Motion

This paper presents a response evaluator as a semi-active control method for base isolated building in long-period earthquake response analysis. The absolute acceleration of each story and relative displacement of an isolated layer are the input signals and switching parameter for the damping coefficient is the output signal of the response evaluator. The response evaluator is designed by a multilayered neural network, and a genetic algorithm is used to adjust the neural network parameters which decide the performance of the response evaluator. Four oil dampers are installed at the isolated layer and each damping coefficient of the dampers is set to different value to correspond to various characteristics of earthquake motions, then the total damping force of the isolated layer is multi-step values regardless of using the oil dampers with two-step damping coefficient. By the numerical simulation with the proposed semi-active control method, both the acceleration of each story and the displacement of isolated layer which are trade-off relations with each other are reduced compared with the acceleration in case of all damping coefficient small (soft) and the displacement of isolated layer in case of all damping coefficient large (hard).

Semi-Active Control for Base Isolated Structure Using Response Evaluator Subjected to Long-Period Earthquake Ground Motion

This paper presents a response evaluator as a semi-active control method for a base isolated building in long-period earthquake response analysis. The absolute acceleration of each story and the relative displacement of an isolated layer are the input signals and the switching parameter for the damping coefficient is the output signal of the response evaluator. The response evaluator is designed by a multilayered neural network, and a genetic algorithm is used to adjust the neural network parameters which determine the performance of the response evaluator. Four oil dampers are installed in the isolated layer and each damping coefficient of the dampers is set to a different value to correspond to the various characteristics of earthquake motions, then the total damping force of the isolated layer is multi-step values, regardless of whether using oil dampers with two-step damping coefficients. By the numerical simulation with the proposed semi-active control method, both the acceleration of each story and the displacement of the isolated layer, which are in a trade-off relationship with each other, are reduced compared with the acceleration in the case of all damping coefficients being small (Soft) and the displacement of the isolated layer in the case of all damping coefficients being large (Hard).

404 地震動の特性を考慮した免震建物の応答評価に基づくセミアクティブ制御(免震I,OS-2 耐震・免震・制震,総合テーマ「伝統を,未来へ!」)

404 地震動の特性を考慮した免震建物の応答評価に基づくセミアクティブ制御(免震I,OS-2 耐震・免震・制震,総合テーマ「伝統を,未来へ!」)

EFFECTS OF THE IRREGULAR UNDERGROUND STRUCTURES OF THE WESTERN EDGE ON SEISMIC MOTION AT THE WESTERN PART IN THE NOBI PLAIN

In this paper, we discuss the propagation process of ground motions generated by two earthquakes through the analysis of seismograms recorded on rock and sediment sites. Significant later phases following the S-wave arrivals in horizontal components often appear in the ground motions recorded in the sedimentary plain. We applied 2-D finite difference method to simulate the later phases during the earthquakes observed at the sediment sites using the subsurface structures derived from the seismic and microtremors prospecting process. The results indicate that when considering basin-excited waves, the characteristics of the simulated waveforms including the later phases display good agreement with the observed seismograms. Moreover, the earthquake motion characteristics were clarified by the propagation process of seismic waves in the western part of Nobi Plain. We also clarified effects of the irregular underground structure on the Basin-Induced Love waves propagation.

Statistical analyses of damages to buildings in the 1988 Saguenay earthquake

The 1988 Saguenay earthquake caused a large variety of geotechnical and structural damage. A total of 1927 claim files, most of which were submitted under a compensation program sponsored by the ministère de la Sécurité publique du Québec, Direction générale de la sécurité civile, have been studied. The results of this study are presented in terms of correlations between damage and geographical distribution, earthquake motion characteristics, soil conditions, and type of structures. Site effects are pointed out as one of the main causes of damage to buildings even at large distances from the epicentre. Key words: Saguenay earthquake, distribution of damage, geotechnical damage, structural damage, site effects.

ボーリング柱状図データベースによるサイスミック・マイクロゾーニング

The data of about 30, 000 borehole records centering around the Metropolitan area has been stored in the database. The data were produced at the fundamental survey for construction of various structures. Regional distribution of the ground properties such as thickness of soft ground, vibrational characteristics of ground, liquefaction potential of sand layer, etc. are grasped from the database.In addition, using the characteristics of earthquake motions in the basement and in the sedimentary layer estimated by the model constructed from the observed data at the network of strongmotions including three deep boreholes, regional distribution of the size of surface ground motions were estimated.

山地, 山沿い地および平野部における地震波形の特徴

山地, 山沿い地および平野部における地震波形の特徴

Earthquake Environment for Physical Design: A Statistical Analysis

A statistical analysis of nationwide seismic activities is made to determine the level and characteristics of earthquake motions to be expected in different geographical locations. Such information is needed to identify the severity of the earthquake threat to telephone facilities and to specify adequate design requirements. This paper describes the essential seismic environment including the expected earthquake-magnitude levels and the corresponding frequency of occurrence for different seismic-risk zones, and the free-field and in-building motions that might be induced by earthquakes. Stochastic models are used to analyze the earthquake-occurrence statistics, and to describe the induced random ground motions. Historical earthquake data are used to verify the theory and to generate information useful for seismic design.

正誤表

正誤表

地震動の周期特性を考慮した地震危険度の表現方法

地震動の周期特性を考慮した地震危険度の表現方法