Seismic isolation of bridges using isolation systems based on flat sliding bearings     

Mauro Dolce  Donatello Cardone  Giuseppe Palermo 《Bulletin of Earthquake Engineering》2007,5(4):491-509

Three different isolation systems (IS’s) for bridges and viaducts are considered in the present study. All of them are made of steel-PTFE sliding bearings (SB) to support the weight of the deck and auxiliary devices, based on different technologies and materials (i.e. rubber, steel and shape memory alloys), to provide re-centring and/or additional energy dissipating capability. An extensive numerical investigation has been carried out in order to (i) assess the reliability of different design approaches, (ii) compare the response of different types of IS’s, (iii) evaluate the sensitivity of the structural response to friction variability due to bearing pressure, air temperature and state of lubrication and (iv) identify the response variations caused by changes in the ground motion, bridge and isolation characteristics. The nonlinear time-history analyses have been carried out using a simplified pier-deck model, where the pier is modelled as an elastic cantilever beam and the mass of the deck is connected to the pier through suitable nonlinear elements, simulating the behaviour of the IS. Both artificial and natural seismic excitations have been used in the nonlinear dynamic analyses.  相似文献   

Polymineralic orientation analysis of magmatic rocks using Electron Back-Scatter Diffraction: Implications for igneous fabric origin and evolution     

I. Romeo  R. Capote  R. Lunar  N. Cayzer   《Tectonophysics》2007,444(1-4):45-62

Electron Back-Scatter Diffraction (EBSD), which provides an easy way of acquiring large numbers of individual crystallographic orientation data from different phases, has been applied to the study of magmatic fabrics. Using this technique, the crystallographic preferred orientation (CPO) of plagioclase, biotite, orthopyroxene, hornblende and quartz in natural tonalites and quartzdiorites (from the Santa Olalla Igneous Complex, SW Iberia) deformed during the magmatic stage have been determined. Plagioclase is the coarser phase defining the main fabric in each sample, whereas biotite can display either the same fabric as plagioclase or a completely different one. The differences between these two phases occur because: (1) smaller phases interact with the larger ones to produce more random orientations, (2) under simple shear, finer phases can completely rotate giving a girdle included in the XZ plane, (3) finer phases can more easily preserve relict fabrics, while the coarser phases are completely reoriented by the last stress tensor. The last phases to crystallize show weak to completely random CPOs (hornblende) or completely random distributions (quartz). The study was completed with a shape preferred orientation analysis using the Intercept Method in order to detect weak magmatic lineations, and numerical modelling simulations of theoretically equivalent simple shear situations for each sample.  相似文献   

柱坐标三维等参元法向载荷等效     

陈荐俊 《地球科学与环境学报》1992,(2)

本文推导了柱坐标中三维等参元载荷等效公式。  相似文献   

How to Choose Priors for Bayesian Estimation of the Discovery Process Model   总被引：1，自引：0，他引：1  

Jingzhen?Xu  Richard?Sinding-LarsenEmail author 《Natural Resources Research》2005,14(3):211-233

The Bayesian version of the discovery process model provides an effective way to estimate the parameters of the superpopulation, the efficiency of the exploration effort, the number of pools and the undiscovered potential in a play. The posterior estimates are greatly influenced by the prior distribution of these parameters. Some empirical and statistical relationships for these parameters can be obtained from Monte Carlo simulations of the discovery model. For example, there is a linear relationship between the expectation of a pool size in logarithms and the order of its discovery, the slope of which is related to the discoverability factor. Some simple estimates for these unknown play parameters can be derived based upon these empirical and statistical conclusions and may serve as priors for the Bayesian approach. The priors and posteriors from this empirical Bayesian approach are compared with the estimates from Lee and Wang's modified maximum likelihood approach using the same data.  相似文献   

台阶式加筋土挡墙的原型试验研究   总被引：2，自引：1，他引：2  

雷胜友 《工程地质学报》2001,9(1):44-50

对一座台阶式钢筋混凝土串联拉筋加筋土挡墙的筋带应力、土侧向压力、土竖向压力及挡墙变形进行了实测和分析, 所得结论可供设计类似支挡结构时参考。  相似文献   

图斑形状特征对原面积中误差公式的修正——一个面积中误差估算模型   总被引：3，自引：0，他引：3  

柯正谊  李子川 《测绘学报》1992,21(1):57-66

本文考虑到多边形图斑形状特征对面积量算误差的显著影响，用一“特征参数”T，将图斑形状特征量化。经参数T修正的面积中误差估算公式有较低的“偏离度”，且数学形式简单，采用修正模型可设定新的面积量算容许误差，并可改进图斑面积平差的传统方法。  相似文献   

中国地区地磁场日变形态的分析   总被引：1，自引：0，他引：1  

冯忠孝  陈英方  蒋伯琴 《地震地磁观测与研究》1992,(5)

根据资料系统地分析了中国地区地磁场 Z 分量 S_q、S_D 时空变化现象及11年变化规律,在此基础上同时研究了出现的低点位移和拉平现象。结果表明,这是多发生在我国北部台站的冬季现象,同时也是迭加在正常地磁场的一种正常变化现象。  相似文献   

Discovery process modeling—A sensitivity study     

Zhuoheng Chen  Richard Sinding-Larsen 《Natural Resources Research》1994,3(4):295-303

Lognormal discovery process modeling characterizes oil and gas discovery as sampling from a lognormal parent distribution with probability proportional to size and without replacement. In this article, we present a sensitivity study that is based on simulated discovery sequences with different assumptions regarding discovery efficiency, exploration status, and the shape of the parent field size distribution. The results indicate that lognormal discovery process modeling provides good overall estimates of the lognormal parameters if the parent field size distribution is lognormal. If the parent field size distribution is Pareto, an underestimation of the play potential may occur if a lognormal discovery process model is applied. Failure of the likelihood value converging to a maximum is more frequent when sample size is small and/or discovery efficiency is low.  相似文献   

Granitoid emplacement during syn-convergent transtension:An example from the Huamenlou pluton in North Qinling,central China     

Yang Li  Wentian Liang  Guowei Zhang  Yazhou Ran  Qi Shen  Jingli Wang  Chunsheng Jin 《地学前缘(英文版)》2018,9(1):191-205

The Huamenlou pluton,is an elongated granite intrusion with high aspect ratio,emplaced within the southern margin of the North Qinling(central China).Here we investigate this pluton through multiple techniques including the fabric study,microstructural observation and zircon geochronology.Our zircon U-Pb data confirm that the granite crystallized at ca.462 Ma which is consistent with the ages of other linear plutons in North Qinling.Microstructural observations of the Huamenlou granites illustrate that the pluton has undergone superimposed deformation during its emplacement,from magmatic to hightemperature solid state conditions.The internal fabric obtained by anisotropy of magnetic susceptibility(AMS)and shape preferred orientation(SPO)show similar results.The fabrics are relatively concordant and generally vary from NE-SW to NEE-SWW which are roughly oblique to the trend of the pluton elongation and the regional structures.Meanwhile,scalar parameters reflect two completely different strain regimes for the pluton and its host rocks,i.e.,the fabrics within host rocks are mainly oblate while the central part of the intrusion displays mainly prolate fabrics.It is inferred that the structural pattern recorded in this pluton was caused by local dextral transtension in consequence of oblique convergence between the South and North China Blocks.We propose that the local transtension in convergence setting probably evolved from vertical extrusion tectonics that provided room for the magma emplacement and imparted prolate fabrics in the Huamenlou pluton.  相似文献   

形状记忆合金（SMA）智能混凝土的研究与应用综述     

王伟  崔迪  王桂萱 《东北地震研究》2012,28(2):72-78

形状记忆合金（SMA）是一种性能良好的智能材料,它与混凝土结构的结合克服了传统混凝土的一些缺陷,并在抗震设计方面体现出强大的优势。通过介绍智能材料结构的发展概况,详细阐述了形状记忆合金的工作原理、特性,根据使用方式的不同划分的内置与外置SMA智能混凝土,以及不同研究者的成果,总结了各自的特点及不足,并探讨了未来的发展方向及研究重点。  相似文献