Study of the earthquake response of pine flat dam

The earthquake response of Pine Flat Dam is examined by a study of time history responses computed for a large set of earthquake ground acceleration records whose time axes have been systematically varied. Linear elastic behaviour is assumed. Topics considered include an investigation of the importance of the presence of water, water compressibility and the vertical component of ground motion; an evaluation of the accuracy of the lumped, added mass representation of the water; and a determination of the intensity of earthquake required to initiate non-linear behaviour in both the dam and water.     

二滩水电站拱坝强震台阵介绍

论证二滩水电站拱坝反应台阵建设的必要性,介绍了台阵的设计安装和组成。最后,通过展示系统2002年4月20日记录到的强地震动加速度记录说明系统已经正常运行。     

强震下地铁车站结构动力响应特性

研究地下结构在地震中的动力响应,对地铁的建设和安全运营有重要的现实意义.根据试验条件和Bockingham定理,作者确定了试验相似比,针对北京地区的地质条件和典型的地铁车站结构进行了大型振动台试验,并对得到的加速度时程进行了分析.通过分析,发现土与地下结构间存在相互作用,但地下结构不会表现出其自振频率,而是随着土体一起振动;在低强度地震下,地下结构对土体影响较小;在高强度地震下,地下结构对土体影响较大;峰值加速度的放大倍数不会超过2,且同一点的放大倍数基本保持不变;随埋深的增加,卓越频率和其振幅会减小,且加速度峰值也有相似的规律.     

Dynamics of the Yenisei and Pur River Deltas

Variations in the mouth areas of the Yenisei and Pur rivers over the period of 50 years were revealed on the basis of comparison of topographic maps prepared in the 1950s and space images made from the Landsat satellite in 1973 (MSS System) and 1999, 2000 (ETM System). Maps of the drainage network dynamics were compiled; they show that, over a period of many years, mouth areas of northern rivers undergo slow but steady changes, which are indicative of the continuing protrusion of deltas into bays at a rate up to 20 m/year, the increment in mouth areas reaching 0.05–0.07% a year. As noted, secondary water streams die off under the condition of flow concentration in main branches, and small islands get integrated. It was found that, over the period under study, natural variations in the level of the receiving water body and human-induced changes in river basins (construction of a chain of reservoirs) did not have considerable impact on dynamic processes occurring in deltas.     

Linear and nonlinear response of concrete slab on CFR dam during earthquake

The joint between concrete slab and rockfill is designed as welded contact in the classical modeling of concrete-faced rockfill (CFR) dams and earthquake response of the CFR dams is determined by this method. In this study, linear and nonlinear response of Torul CFR Dam including interface element between concrete slab and rockfill were investigated for the duration of strong seismic excitation. The finite element analyses were performed by employing both cases, empty and full reservoir, to research the effect of the reservoir water on the earthquake response of the dam. The reservoir water was modeled with fluid finite elements by the Lagrangian approach. The Drucker-Prager model was used in nonlinear analyses for concrete slab, rockfill and soil materials. According to finite element analyses, displacement and stress components were increased by hydrodynamic pressure. The nonlinear response of the concrete slab was monitored about the peak ground acceleration (pga). This study reveals that the size of sliding zone increases with increasing acceleration amplitudes.     

神户大开地铁车站的地震反应分析

本文对阪神地震中大开地铁车站的地震破坏机理进行了分析，复反应分析方法的计算结果表明大开车站的中柱在水平和竖向地震动作用下产生的较大内力，导致了整个地下结构的破坏；计算结果还表明在阪神地震中，竖向地震动作用下地下结构所产生的内力比水平地震动作用下产生的内力要大。     

The source and aftershocks of the Altai (Chuya) earthquake of 2003

Results derived from processing of data of field observations in the epicentral zone of the Altai earthquake of 2003 are presented. Accurate location of aftershocks showed that their spatial distribution is in good agreement with the source rupture outcropping on the Earth’s surface. According to aftershock data, the source had a length of 75 km and a maximum width of 20 km and extended in the vertical direction for 17 km; the displacement in the source averaged 2.5 m. Clusters identified in the aftershock cloud define variously dipping planes. The location of hypocenters by regional, national, and global seismic networks is not accurate enough to examine spatial features of the aftershocks.     

漫湾水电站拦污栅框架的动力模型试验

根据动力核模型相似原理，通过对漫湾水电站拦污栅框架的动力模型试验，把握了解其自振特性和地震响应，为拦污栅框架设计提供了可靠依据，结果应用于工程实际，对类似拦污栅架的抗震设计有参考作用。     

Shear hysteretic elasto-plastic earthquake response of soil systems

An analytical/numerical procedure is developed to calculate the shear hysteretic elasto-plastic earthquake response of soil systems. Dynamic level ground response as well as earth-dam response is evaluated on the basis of the analytical one-dimensional (ID) shear-beam and shear-wedge models respectively. Soil is modelled as an elasto-plastic hysteretic material following the principles of flow or incremental plasticity. Stiffness and strength degradation of this material may be specified as a function of accumulated plastic strain and associated pore-pressure build-up. The entire numerical procedure may be executed on a personal computer and consequently qualifies as a versatile tool in conducting preliminary design calculations or parametric-type investigations. Using this procedure, the responses of the Mexico City SCT site during the September 19, 1985 earthquake, and the California Wildlife site during the November 24, 1987 earthquake are computed and compared to those actually observed.     

Numerical investigation of the response of the Yele rockfill dam during the 2008 Wenchuan earthquake

In this paper the seismic response of a well-documented Chinese rockfill dam, Yele dam, is simulated and investigated employing the dynamic hydro-mechanically (HM) coupled finite element (FE) method. The objective of the study is to firstly validate the numerical model for static and dynamic analyses of rockfill dams against the unique monitoring data on the Yele dam recorded before and during the Wenchuan earthquake. The initial stress state of the dynamic analysis is reproduced by simulating the geological history of the dam foundation, the dam construction and the reservoir impounding. Subsequently, the predicted seismic response of the Yele dam is analysed, in terms of the deformed shape, crest settlements and acceleration distribution pattern, in order to understand its seismic behaviour, assess its seismic safety and provide indication for the application of any potential reinforcement measures. The results show that the predicted seismic deformation of the Yele dam is in agreement with field observations that suggested that the dam operated safely during the Wenchuan earthquake. Finally, parametric studies are conducted to explore the impact of two factors on the seismic response of rockfill dams, i.e. the permeability of materials comprising the dam body and the vertical ground motion.     

Impact of hydroelectric power releases on the morphology and sedimentology of the bed of the Warche River (Belgium)

The Butgenbach dam on the Warche River was built in 1932 in order to maintain a suf?cient supply of water to the Robertville reservoir situated 7 km downstream, for the production of hydroelectricity. During winter months, releases are made almost every day from the Butgenbach dam. From a hydrological point of view, this has resulted in signi?cantly reducing the number of discharges that are higher than bankfull. Despite the reduction in peak discharge, there is a signi?cant increase in the number of ef?cient discharges (0·6 bankfull). The impacts of these hydrological modi?cations on the bed morphology and sedimentology below the Butgenbach dam have been studied and the following geomorphological modi?cations have been identi?ed: a doubling of the width of the channel in 45 years, a reduction in the number of rif?es and pools, an increase in the number of gravel bars and islets and an increase in bedrock outcrops in the channel. Moreover, the ?nest bed particles are mobilized by the almost daily releases, inducing a signi?cant increase in bed‐material size sorting. The reduction of sinuosity and the disappearance of bed differentiation and rif?e/pool sequences have produced a diminution of bed roughness and an increase of the competence of the river. Thus relatively small ?oods can remove the armoured layer. Copyright © 2003 John Wiley & Sons, Ltd.     

The effects of repeated earthquake ground motions on the non‐linear response of SDOF systems

In many parts of the world, the repetition of medium–strong intensity earthquake ground motions at brief intervals of time has been observed. The new design philosophies for buildings in seismic areas are based on multi‐level design approaches, which take into account more than a single damageability limit state. According to these approaches, a sequence of seismic actions may produce important consequences on the structural safety. In this paper, the effects of repeated earthquake ground motions on the response of single‐degree‐of‐freedom systems (SDOF) with non‐linear behaviour are analysed. A comparison is performed with the effect of a single seismic event on the originally non‐damaged system for different hysteretic models in terms of pseudo‐acceleration response spectra, behaviour factor q and damage parameters. The elastic–perfect plastic system is the most vulnerable one under repeated earthquake ground motions and is characterized by a strong reduction of the q‐factor. A moment resisting steel frame is analysed as well, showing a reduction of the q‐factor under repeated earthquake ground motions even larger than that of an equivalent SDOF system. Copyright © 2002 John Wiley & Sons, Ltd.     

Stochastic earthquake response of secondary systems in base-isolated structures

This paper studies the stochastic responses of secondary systems in base-isolated shear beam structures. A number of base isolation systems such as the laminated rubber bearing (LRB), the resilient-friction base isolator (R-FBI) with or without sliding upper plate, and the EDF system are considered. The stochastic models for the El Centro 1940 and the Mexico City 1985 earthquakes which preserve the non-stationary evolutions of amplitude and frequency content of ground accelerations are used as earthquake excitations. The technique of equivalent linearization is utilized and the mean-square response statistics of secondary systems and primary structure are evaluated. The accuracy of the linearization scheme is verified by comparison with the Monte Carlo simulation results. Statistically estimated peak responses of the secondary system are evaluated and the results are compared with the response spectra for actual earthquake accelerograms. It is shown that the use of base isolation systems, generally, provides considerable protection for structural contents. In particular, the LRB system is remarkably effective in reducing responses of secondary systems. Results for the Mexico City earthquake show that the base-isolated structures are sensitive to long period ground excitations.     

核电厂堆芯燃料组件地震反应分析

核电厂堆芯燃料组件在强震作用下难以避免地将产生摩擦、滑移和相互间的碰撞等非线性反应。关于燃料组件之间以及燃料组件与围板之间的碰境模拟对燃料给件地震反应的影响已有计算分析成果,但量,由于摩擦、滑移引起的燃料组件的非线性动力特性在燃料组件地震反应的现有计算模型中还未得到考虑。本文基于试验测定的燃料组件的非线性动力特性,提出了考虑上述因素的燃料组件地震反应分析方法。     

Dynamic response of concrete face rockfill dam affected by polarity reversal of near-fault earthquake

In China, an increasing number of high concrete face rockfill dams(CFRDs) are located in high intensity earthquake zones, some of which are close to the seismic fault line. Recordings suggest that near-fault ground motions are characterized by large one-sided velocity pulses. The conventional dynamic analysis of dams, however, neglects the features of strong ground movements. In this study, under different ground motion levels some numerical dynamic studies considering the one-sided broadband pu...     

液化大变形条件下地铁车站结构动力反应大型振动台试验研究

本文对浅埋于可液化南京细砂地基中的地铁车站结构的大型振动台试验结果进行了进一步的整理,主要分析了地铁车站结构侧向地基土发生液化大变形时车站结构的应变反应、加速度反应和土与结构侧墙之间接触面的动土压力反应,结果表明:地铁车站结构侧向土体发生液化大变形时,地基土的大变形造成地铁车站结构中柱和侧墙都发生较大的不可恢复的残余变形;在侧墙底部记录的动土压力反应幅值明显比中部和顶部处记录的值要大,中板处的峰值加速度都比底板处的对应值要大。     

Formation of Frazil Ice and Ice Jams on the Rivers of the Yenisei River Basin

The effect of different factors on the duration of spring ice jams and the flood water level in the Siberian rivers is considered. Observational data on the frequency of ice jams of different probabilities within some reaches of the Yenisei River are presented.     

Analytical earthquake response of 1D hybrid base isolation systems

The work presents several dynamic analyses of an actual base isolation system previously identified by using a non-linear 1D model and full scale free vibration tests. After a short introduction to the building and the base isolation system considered, reference is made to previous studies where the model used was developed. The analytical model, originally derived for free vibration analyses and system identification applications, is extended in the present paper to earthquake response simulations. First a theoretical harmonic ground motion is considered, in order to identify resonance conditions for the system and stress how these should be avoided in actual design, by carefully studying the seismological and site conditions. The response of the system to a nearly harmonic natural ground motion is then predicted. Next the performance of the system under several significant ground motions from the Friuli 1976, Irpinia 1980 and L'Aquila 2009 earthquakes is considered, and the reasons for its satisfactory or unsatisfactory behaviour are pointed out and explained. Means for correcting unsatisfactory performances are also suggested and discussed. The behaviour of the system under near fault records from the L'Aquila 2009 earthquake is then considered, the conditions leading to the maximum demands are highlighted and the reasons behind them are clearly explained. Finally the 1D model presented is used to predict the 2D response to 2D ground motions.     

The effect of spatially varying earthquake ground motions on the stochastic response of bridges isolated with friction pendulum systems

In this paper, a comprehensive investigation of the effect of spatially varying earthquake ground motions on the stochastic response of bridges isolated with friction pendulum systems is performed. The spatially varying earthquake ground motions are considered with incoherence, wave-passage and site-response effects. The importance of the site-response effect, which arises from the difference in the local soil conditions at different support points of the isolated bridge, is investigated particularly. Mean of maximum and variance response values obtained from the spatially varying earthquake ground motions are compared with those of the specialised cases of the ground motion model. It is shown that site-response component of the spatially varying earthquake ground motion model has important effects on the stochastic response of the isolated bridges. Therefore, to be more realistic in calculating the isolated bridge responses, the spatially varying earthquake ground motions should be incorporated in the analysis.     

Analysis of absorption effects on the dynamic response of dam reservoir systems by boundary element methods

Using reciprocal theorems for dynamic and static boundary value problems, boundary integral equations are presented for wave propagation in elastic, isotropic media and compressible, inviscid fluids in the time domain as well as in the frequency domain. For the analysis of fluid–soil and fluid–structure systems, suitable coupling conditions are prescribed along the interfaces. The numerical treatment of the boundary integral equations consists of a point collocation and of a discretization of the boundary, in which constant and linear approximation functions are assumed. Step-by-step integration is applied to the time-dependent equations, where again the states are taken to be linear and constant over each time interval. These boundary element procedures are used to analyse the response of dams due to horizontal and vertical ground motions considering dam–water interaction and absorption of hydrodynamic pressure waves at the reservoir bottom or at the far end into the soil medium. Both the frequency response and the impulse generated transient response are investigated.