库尔勒数字地震台台基噪声分析

选取库尔勒地震台FBS—3数字地震仪不同时段的无震记录资料，运用傅里叶变换对其台基噪声进行频谱分析，并计算台基的平均噪声水平及仪器的实际动态范围。库尔勒地震台数字地震仪台基噪声主要来自随机干扰，噪声频段相对稳定，噪声幅度随时段有所变化。观测系统实际动态范围符合数字地震仪架设的要求。     

江西数字测震台网建设效益分析

介绍“十五”江西数字测震台网建设的基本情况,分析台站布局、观测动态范围和台基环境地噪声水平对台网地震监测能力的影响,阐述江西数字测震台网技术成果及所取得的社会经济效益.实现与邻省台网的联网与数据共享后,台网监测能力得到提高.     

The declining but non-rejuvenating base level—The Lisan lake,the Dead Sea area,Israel

Laboratory experiments investigating the effects of a lowering base level do not simulate natural eustatic lowering along concave river profiles. The field data on this issue are also quite limited. In evaluating the control exercised by lowering base level on a drainage network, distinction must be made between its influence and those of other hydromorphological processes operating within the basin. Field data on morphological relations, based on photogrammetric mapping and longitudinal profiling, have been gathered in the Dead Sea area, Israel, where a rapid fall in base level has occurred during the Holocene. The study area is an entrenched fan delta with a sequence of 14 unpaired fan terraces which die out at intersection points within an alluvial fan system. The results suggest that the intersection points did not function as base levels. The receding base level played only a passive role, allowing entrenchment without transmitting a head-cutting feedback basinwards. The arid environment caused a delay in transmission of information through the system. The results support the model of short, episodic, and discontinuous erosional events, inherent in the evolution of drainage basins. It is suggested that base level effects in temperate and humid regions are not transferrable to arid zones.     

Preliminary study on variation characteristics of ocean tide dynamic stress in crust and its relationship with earthquakes

~~Preliminary study on variation characteristics of ocean tide dynamic stress in crust and its relationship with earthquakes@陆明勇$China Center for Earthquake Disaster Emergency and SAR,Beijing 100049,China @郑文衡$Huazhong University of Science and Technology,Wuhan 430074,China①Strong earthquake catalogues in China. Earthquake catalogues reported monthly by Center for Analysis and Prediction, CEA. ①YI Zhi-gang. Institute of Crustal Dynamics, China Earthquake Administrati…     

模型化方法对钢筋混凝土框架地震反应的影响分析

结构非线性动力分析平台OpenSees具备丰富的材料、单元、模型化方法等分析选项和强大的求解功能。在OpenSees平台,对按我国规范设计的八度区二级和九度区一级典型钢筋混凝土框架结构进行了一系列罕遇烈度地震作用下的非线性动力反应分析。通过对分析结果的对比、判断,并结合各种模型化方法对结构地震反应的影响方式进行解释,从顶点侧移、层间侧移角、基底剪力、框架塑性铰分布等方面揭示了不同单元力学模型以及箍筋、板筋对结构整体、局部地震反应的影响规律。     

Optimal design and seismic performance of tuned mass damper inerter (TMDI) for structures with nonlinear base isolation systems

The tuned mass damper inerter (TMDI) couples the classical tuned mass damper (TMD) with an inerter, a mechanical device whose generated force is proportional to the relative acceleration between its terminals, thus providing beneficial mass‐amplification effects. This paper deals with a dynamic layout in which the TMDI is installed below the isolation floor of base‐isolated structures in order to enhance the earthquake resilience and reduce the displacement demand. Unlike most of the literature studies that assumed a linearized behavior of the isolators, the aim of this paper is to investigate the effectiveness of the TMDI while accounting for the nonlinearity of the isolators. Two nonlinear constitutive behaviors are considered, a Coulomb friction model and a Bouc‐Wen hysteretic model, representative of friction pendulum and of lead‐rubber‐bearing isolators, respectively. Optimal design is based on the stochastic dynamic analysis of the system, by modeling the base acceleration as a Kanai‐Tajimi filtered stationary random process and resorting to the stochastic linearization technique to handle the nonlinear terms. Different tuning criteria based on displacement, acceleration, and energy‐based performance indices are defined, and their implications in a design process are discussed. It is proven that the improved robustness of the TMDI reduces its performance sensitivity to the tuning frequency and to the earthquake frequency content, which are well‐known shortcomings of TMD‐like systems. This important feature makes the TMDI particularly suitable for nonlinear base‐isolated structures that are affected by unavoidable uncertainties in the isolators' properties and that may experience changes of isolators effective stiffness depending on the excitation level.     

广西数字测震台网建设成果及效益分析

介绍了"十五"广西数字测震台网建设的基本情况,分析了台站布局、观测动态范围和台基环境地噪声水平对台网地震监测能力的影响。实现与邻省台网和地方社会台网的联网与数据共享后,台网监测能力得到进一步提高。以广西数字测震台网投入运行前后记录到的地震情况,阐述了广西数字测震台网技术成果及所取得的社会经济效益。     

动力相互作用分析中无质量地基的应用研究

关于结构-地基的动力相互作用分析已经提出了很多方法，但由于方法复杂而没有得到广泛应用，无质量地基模型仍然是应用最为广泛的近似方法。本文通过结构-地基的动力相互作用分析公式的推导，详细阐明了考虑无限地基影响的动力相互作用分析中无质量地基的概念和应用范围，并通过算例进行了说明。     

新疆数字地震台站观测动态范围和台基噪声的分析

介绍了新疆数字地震台仪器的配置,对新疆23个数字地震台站台基噪声进行分析计算。台站的观测动态范围,反映了观测仪器本身的性能和台基环境干扰背景的水平,有效动态范围大小反映记录地震信号的最大能力。台站(台网)的监测能力不仅取决于仪器的性能,而且还与台基的噪声背景有关。得出了各地震台台基的脉动噪声的均方根值、观测动态范围、地噪声功率谱。有效观测动态范围的大小与数字地震仪的种类和配置有关。新疆23个数字地震台中的21个台的台基地动噪声在1~20 Hz内符合中国数字测震台网技术规程的要求,而另外2个台,即二宫和石河子数字地震台没有达到规定指标。     

Rocking vibrations of a rigid embedded foundation in a poroelastic soil layer

An approximate analytical method is presented for the dynamic response of a rigid cylindrical foundation embedded in a poroelastic soil layer under the excitation of a time-harmonic rocking moment. The soil underlying the foundation base is represented by a single-layered poroelastic soil based on rigid bedrock while the soil along the side of the foundation is modeled as an independent poroelastic stratum composed of a series of infinitesimally thin layers. The accuracy of the present solution is verified by comparisons with existing solutions obtained from other researchers. Numerical results for the rocking dynamic impedance and dynamic response factor are presented to demonstrate the influence of nondimensional frequency of excitation, poroelastic soil layer thickness, depth ratio of the foundation and internal friction of the poroelastic soil.     

Dynamic characteristics of lateral load-deflection relationships of flexible piles

Most offshore platforms are supported on long and large-diameter piles with variable wall-thickness along the length, and soil properties varying with depth. The design and analyses of these piles are made by modelling the soil-pile system with a beam-on-Winkler foundation. Therefore, evaluation of appropriate soil-pile springs for use in such analyses is a matter of concern. Fundamental characteristics of dynamic lateral load-deflection relationships for piles were studied analytically considering the soil-pile-structure interaction under seismic loading conditions. The soil layer was assumed homogeneous, linearly elastic with hysteretic type material damping, and overlying a rigid base. A superstructure with multi-degrees of freedom was supported by a single vertical pile hinged at the rigid base. Parametric studies were carried out to identify the influence of the system parameters on the behaviour of the dynamic lateral load-deflection relationships of piles. The lateral load-deflection relationships vary considerably with depth and are influenced not only by the dynamic properties of soil but also by the structural properties of a pile and loading conditions. These lateral load-deflection relationships can be used to define the soil-pile springs for the seismic response analysis of a soil-pile-structure system, and the results can be extended to problems with soil profiles with layering and non-linearity.     

非平稳时间序列的动态水位神经网络预报模型

水文预报系统是一个复杂的非线性动力学过程,站点水位受各种因素的影响不仅呈现出非平稳动态随机变化特性,而且各因素间的关系也很难确定。淮河流域五河站水位由于受到洪泽湖回水影响及季节性的影响,也呈现出这一动力学的非平稳特性,因此本文在考虑了相关站点和回水影响的基础上,建立了一种多站变量时间序列的神经网络预报模型,预报结果表明该方法预测效果较好,运行简单。     

Centrifuge modeling of batter pile foundations under sinusoidal dynamic excitation

Batter pile (or inclined pile) foundations are widely used in civil engineering structures. However, their behavior under dynamic loadings is not yet thoroughly understood. This paper presents an experimental work on the behavior of batter and vertical piles considering dynamic soil-pile-superstructure interactions. A series of dynamic centrifuge tests were performed using sinusoidal excitations. The influence of the base shaking (frequency content and amplitude) and of the height of the center of gravity of the superstructure is investigated. Seismic responses are analyzed considering the pile cap displacements and forces (total base shear, overturning and residual moments, axial forces). It is found that in certain cases batter piles play a beneficial role on the dynamic behavior of the pile foundation system. This novel experimental work provides an important database on the behavior of batter pile foundations under dynamic loadings.     

Accuracy of discharge determined from a rating curve

ABSTRACT

An error analysis shows that three types of errors influence the random error of a single discharge measurement determined from a rating curve. They are rating curve error, water level measurement error and an error caused by ignoring all physical parameters, other than water level, that affect discharge. Methods in the literature for evaluating the first two types of errors are reviewed and a method for evaluating the third type is given. The error of average discharge for an arbitrary period is also considered.     

稳态机械阻抗法动测规律的应用研究

利用改进的复合平面应变轴对称的Ｂ－Ｎ法，计算得到了桩顶动力复刚度公式，并通过计算机分析得到完整桩、缩颈桩、断桩、离析桩、扩颈桩的速度导纳曲线规律及动刚度的变化规律，并结合实例对其应用作了说明．     

Behavior of braced wall embedded in saturated liquefiable sand under seismic loading

It is well known that the generation of excess pore water pressure and/or liquefaction in foundation soils during an earthquake often cause structural failures.This paper describes the behavior of a small-scale braced wall embedded in saturated liquefiable sand under dynamic condition.Shake table tests are performed in the laboratory on embedded retaining walls with single bracing.The tests are conducted for different excavation depths and base motions.The influences of the peak magnitude of the ground motions and the excavation depth on the axial forces in the bracing,the lateral displacement and the bending moments in the braced walls are studied.The shake table tests are simulated numerically using FLAC 2D and the results are compared with the corresponding experimental results.The pore water pressures developed in the soil are found to influence the behavior of the braced wall structures during a dynamic event.It is found that the excess pore water pressure development in the soil below the excavation is higher compared to the soil beside the walls.Thus,the soil below the excavation level is more susceptible to the liquefaction compared to the soil beside the walls.     

维尼迪科夫调和分析对大甸子井水位潮汐因子和相位的气象影响研究

利用维尼迪柯夫潮汐调和分析方法计算内蒙古大甸子井水位原始资料和剔除气压、降雨资料后的潮汐因子和相位。结果显示,两种情况下得到的潮汐因子和相位具有较好的一致性,说明采用维尼迪柯夫潮汐调和分析方法得到的结果基本不受降水、气压等因素的影响。这对于缺少气压和降水等辅助观测的水位观测资料,使用原始资料进行维尼迪科夫潮汐调和分析,可获取比较可靠的潮汐因子和相位参数。     

Pseudo‐dynamic testing of a concrete gravity dam

Inspired from the simplified single degree of freedom modeling approach used in the preliminary design of concrete gravity dams, a pseudo‐dynamic testing method was devised for the seismic testing of a concrete gravity dam section. The test specimen was a 1/75 scaled section of the 120‐m‐high monolith of the Melen Dam, one of the highest concrete gravity dams to be built in Turkey. The single degree of freedom idealization of the dam section was validated in the first stage of the study using numerical simulations including the dam–reservoir interaction. Afterwards, pseudo‐dynamic testing was conducted on the specimen using three ground motions corresponding to different hazard levels. Lateral displacement and base shear demands were measured. The crack propagation at the base of the dam was monitored with the measurement of the crack widths and the base sliding displacements. After the pseudo‐dynamic loading, a static pushover test was conducted to determine the reserve capacity of the test specimen. Despite major cracking at the base of the monolith, neither significant sliding nor a stability problem that might jeopardize the stability of the dam was observed. Copyright © 2015 John Wiley & Sons, Ltd.     

对利用跨断层基线和水准测量资料推算断层活动参数公式的改进

分析了利用两条跨断层基线和水准测量资料推算断层三维活动参数传统公式存在的问题,指出传统的计算公式实际是一个要求两侧点位处于同一水平面时的近似公式。本文对这一公式重新进行了严格的数学推导,得到了适用于一般情况的改进后的计算公式,并以实际算例指出传统公式对计算结果可能造成的误差量级。     

抗差自适应Kalman滤波在动态变形监测中的应用研究

抗差自适应Kalman滤波算法中,抗差等价权矩阵和自适应因子的计算,要求观测信息具有多余观测量且准确可靠,但在动态变形监测应用中,通常滤波观测值仅为三维坐标且存在较强噪声和粗差的影响。为此,先对该算法中的自适应因子和抗差等价权矩阵的计算进行研究和改进,然后计算了某高速公路边坡的GPS动态监测数据。结果表明,抗差自适应Kalman滤波能够有效地抵制动态变形监测中观测值异常的影响。