Current state of integrated earthquake simulation for earthquake hazard and disaster

This paper presents the current state of integrated simulation for earthquake hazard and disaster. This simulation takes advantage of the macro–micro analysis method; this method estimates an earthquake’s strong motion with high spatial and temporal resolution, using the bounding medium theory to obtain optimistic and pessimistic estimates of expected strong motion distribution and the singular perturbation expansion that results in an efficient multi-scale analysis. Integrated earthquake simulation calculates seismic responses for all structures in a target area, inputting simulated strong ground motion to a structure analysis method that is plugged into the system by means of a wrapper; a suitable method, linear or nonlinear, is chosen depending on the type of the structure. The results of all simulations are visualized so that residences and government officials can share a common recognition of earthquake hazard and disaster. Two examples of this integrated earthquake simulations are presented; one is made by plugging nonlinear structure analysis methods into the system, and the other is made for an actual city, the computer model of which is constructed with the help of available geographical information systems.     

悬挂结构体系地震响应特性及其突变性分析

对现有悬挂结构动力分析模型作了改进,引入了悬挂子结构的随动刚度,将子结构对主结构的非线性驱动力添加到运动方程中。用数值解法给出了悬挂结构体系的地震响应分析,进而给出了振幅与频率响应的计算结果。分析了结构响应突变的复杂特性,结果表明体系参数的微小变化使响应振幅及其突变值等特性产生明显变化,反映出结构体系的地震响应特性对参数变化非常敏感。另外,当吊杆长度较大时,非线性参数较小,结构的突变现象消失,产生"伪线性"性质。     

Stochastic modeling of Iranian earthquakes and estimation of ground motion for future earthquakes in Greater Tehran

Strong-motion data from eight significant well-documented earthquakes in Iran have been simulated using a stochastic modeling technique for finite faults proposed by Beresnev and Atkinson [Bull Seismol Soc Am 87 (1997) 67–84; Seism Res Lett 69 (1998) 27–32]. The database consists of 61 three-component records from eight earthquakes of magnitude ranging from M 6.3 to M 7.4, recorded at hypocentral distances up to 200 km. The model predictions are in good agreement with available Iranian strong-motion data as evidenced by near-zero average of differences between logarithms of the observed and predicted values for all frequencies. The strength factor, sfact, a quantity that controls the high-frequency radiation from the source is determined, on an event-by-event basis, by fitting simulated to observed response spectra.     

Stochastic dynamic response of dam–reservoir–foundation systems to spatially varying earthquake ground motions

In this paper, stochastic dynamic responses of dam–reservoir–foundation systems subjected to spatially varying earthquake ground motions are investigated using the displacement-based fluid finite elements. For this purpose, variable-number-node two-dimensional (2D) fluid finite elements based on the Lagrangian approach is programmed in FORTRAN language and incorporated into a computer program SVEM, which is used for stochastic dynamic analysis of solid systems subjected to spatially varying earthquake ground motion. The spatially varying earthquake ground motion model includes incoherence, wave-passage and site-response effects. The incoherence effect is examined by considering the Harichandran and Vanmarcke coherency model. The effect of the wave passage is investigated by using various wave velocities. Homogeneous medium and firm soil types are selected for considering the site-response effect where the foundation supports are constructed. The Sar?yar concrete gravity dam, constructed in Turkey is selected for numerical example. The ground motion is described by filtered white noise and applied to each support point of the 2D finite element model of the dam–reservoir–foundation system. The record of Kocaeli earthquake in 1999 is used in the analyses. Displacements, stresses and hydrodynamic pressures occurring on the upstream face of the dam are calculated for four cases. It is concluded that spatially varying earthquake ground motions have important effects on the stochastic dynamic response of dam–reservoir–foundation systems.     

Partitioned multiobjective risk modeling of carcinogenic compounds in groundwater

Quantifying human cancer risk arising from exposure to contaminated groundwater is complicated by the many hydrogeological, environmental, and toxicological uncertainties involved. In this study, we used Monte Carlo simulation to estimate cancer risk associated with tetrachloroethene (PCE) dissolved in groundwater by linking three separate models for: (1) reactive contaminant transport; (2) human exposure pathways; and (3) the PCE cancer potency factor. The hydrogeologic model incorporates an analytical solution for a one-dimensional advective–dispersive–reactive transport equation to determine the PCE concentration in a water supply well located at a fixed distance from a continuous source. The pathway model incorporates PCE exposure through ingestion, inhalation, and dermal contact. The toxicological model combines epidemiological data from eight rodent bioassays of PCE exposure in the form of a composite cumulative distribution frequency curve for the human PCE cancer potency factor. We assessed the relative importance of individual model variables through their correlation with expected cancer risk calculated in an ensemble of Monte Carlo simulations with 20,000 trials. For the scenarios evaluated, three factors were most highly correlated with cancer risk: (1) the microbiological decay constant for PCE in groundwater, (2) the linear groundwater pore velocity, and (3) the cancer potency factor. We then extended our analysis beyond conventional expected value risk assessment using the partitioned multiobjective risk method (PMRM) to generate expected-value functions conditional to a 1 in 100,000 increased cancer risk threshold. This approach accounts for low probability/high impact outcomes separately from the conventional unconditional expected values. Thus, information on potential worst-case outcomes can be quantified for decision makers. Using PMRM, we evaluated the cost-benefit relationship of implementing several postulated risk management alternatives intended to mitigate the expected and conditional cancer risk. Our results emphasize the importance of hydrogeologic models in risk assessment, but also illustrate the importance of integrating environmental and toxicological uncertainty. When coupled with the PMRM, models integrating uncertainty in transport, exposure, and potency constitute an effective risk assessment tool for use within a risk-based corrective action (RBCA) framework.     

方钢管混凝土柱的延性系数

在空钢管中填充混凝土可以避免或延缓钢管早地发生局部屈曲,可以有效地提高构件的延性,从而增强构件的抗震性能,本文研究钢管混凝土桩的延性性能,本文首先提出方钢管混凝土柱延性系数的计算方法,然后,在大规模参数分析结构的基础上,考察了轴压比,长细比,含钢率,钢材屈服极限和混凝土抗压强度等参数对延性系数的影响规律,本文的研究成果可供有关工程实践参考。     

Characteristics of annual runoff variation in major rivers of China

The statistical properties of annual runoff in major rivers of China are studied based on the theory of stochastic process and technology of time series analysis. These properties include the characteristics of intra‐annual and inter‐annual variations of runoff, trends, abrupt changes and periodicities. The new findings from the intensive calculations and appropriate analysis of data in longer period are as follows: (i) compared with the nonuniformity of intra‐annual runoff before 1980, the nonuniformity of intra‐annual runoff in China generally decreased after 1980, except for Huaihe River and Songhua River; (ii) compared with the annual runoff before 1980, the annual runoff in China generally decreased after 1980 except for WangJiaba station in Huaihe River and Ha‐Erbin station in Songhua River; the frequency of continuous low flow and continuous high flow in Haihe River and the downstream of Yellow River is higher than those in other rivers in China; (iii) annual runoff shows a downward trend in major rivers of China especially in Haihe River, Liao River and the midstream and downstream of Yellow River; (iv) there exist certain abrupt changes of annual runoff in major rivers of China; the abrupt change‐points are different among different river basins; and (v) almost periodicities of annual runoff sequences in major rivers of China are generally 20 years below, that is, 3~7 and 12~20 years. The reasons for these changes are mainly caused by climate change and human activities. Copyright © 2011 John Wiley & Sons, Ltd.     

基于模拟退火算法的随机模拟方法研究

随着油气田开发难度的加大和技术的进步,储层随机建模技术已经成为储层表征的主要手段.基于地质统计学理论的认识,并结合模拟退火算法,本文研究了退火随机模拟储层地质模型,其结果表明该方法是一种易理解、易实现、较灵活、适应性强、较实用的算法.应用该方法可以建立渗透率、孔隙度、含油饱和度,以及波阻抗等参数的空间分布模型,这些模型很好的保持了已知数据所反映的储层空间特征,并真实地展现了各种参数在储层内的分布,为油气田储层预测和开发提供依据.     

多球面滑动摩擦隔震支座的设计原理和理论模型

介绍一种用于桥梁抗震的多球面滑动摩擦隔震支座,分析这种支座的设计原理,阐明其构造特点,分析了其工作机理和滑动隔震过程,并由此建立了该隔震支座的力—位移关系恢复力模型。理论分析表明,该支座除具备完善的减隔震支座所要求的功能之外,还构造简单、隔震机理清楚、数学物理模型明确,能够满足实际应用中简单性的要求。此外,该支座在不同强度的外部激励下,可以表现出不同的阻尼和刚度。并且具备单独优化性能,即该支座可以基于多性能目标或多水准地震,对于给定的桥梁隔震系统的各个参数分别进行优化。这两种特性使得该支座适合多水准地震动作用下,基于性能的隔震桥梁抗震设计。