基于场地-结构整体模型的桩基斜拉桥地震反应分析方法

针对我国普遍采用的大跨度桩基桥梁,应用无限元有限元土体边界、桩土面面接触算法和显式求解技术,提出了场地结构整体模型的地震反应分析方法.以一座主跨为202.5 m+300.0 m的独塔斜拉桥为工程实例,构建了河谷场地桥梁整体有限元动力模型,研究了二维河谷场地对该斜拉桥纵向地震反应的影响,分析了基础附近扰动场地震动的特点.结果表明,场地中不同河岸高度和二维土层分布会对主塔处地震动的短周期分量产生一定影响,对结构短周期振型产生的地震力有较大影响;扰动场的地震动中接近基础振动频率的分量得到了加强,和自由场的地震动有显著区别,但长周期的分量变化较小.     

可液化河谷场地不同形式梁式桥的地震反应

场地液化对河谷场地中不同结构体系、不同基础形式的梁式桥的地震反应可能具有不同程度的影响.针对该问题,以典型可液化河谷场地三跨梁式桥为背景,建立了二维场地-桥梁结构一体化有限元模型,包括群桩基础简支梁桥、群桩基础连续梁桥和桩柱式基础简支梁桥3种桥型,并进行非线性地震反应分析.从场地和桥梁震后变形、桩基础变形分布、桥墩漂移率、滑动支座位移和桥台伸缩缝位移等方面,探究不同形式梁桥的地震反应规律,重点揭示场地液化对不同形式梁式桥地震反应的影响规律.结果表明:场地液化会显著增大群桩基础简支梁桥的落梁风险,群桩基础连续梁桥受场地液化的影响次之,桥台处的落梁、台梁碰撞风险也较大,而桩柱式基础简支梁桥受场地液化的影响较小.     

三维河谷场地效应对钢管混凝土空间组合桁架连续梁桥地震响应的影响

为揭示三维河谷场地"钢管混凝土空间组合桁架连续梁桥"地震响应规律,以京昆高速公路"干海子特大桥"为工程背景,建立三维河谷场地-多跨连续梁桥动力有限元计算模型;结合黏弹性人工边界及相应的地震动等效输入技术,研究三维河谷场地放大效应对连续梁桥地震响应影响,并和一致激励、二维河谷场地效应进行比较.结果表明:较一致激励,三维河谷场地效应作用下,该类桥梁低墩较高墩对地震动的敏感性增大,且在墩高突变区域最为明显;较一致激励,多点激励下,三维河谷场地效应显著增大了多数桥墩、梁跨的位移和内力,且对墩高突变处低墩、梁跨的放大作用最为明显;较二维河谷场地效应,三维河谷场地效应减小山坡上所有观测值,增大谷底处墩底剪力、墩底弯矩、墩底轴力、墩顶位移,减小谷底处跨中纵向位移、跨中下弦杆和斜腹杆轴力,且在坡顶附近放大效应有所减弱,在谷底较厚低波速沉积层处地震动放大效应更为明显,因此实际处于复杂形状河谷场地结构进行抗震分析宜建立三维模型分析.     

软土场地桩-土-LNG储罐地震响应及场地放大效应分析

目的研究中软场地上大型LNG储罐的地震响应,分析桩土相互作用对上部结构的影响.方法利用有限元软件ADINA建立了1. 6×105m3刚性基础储罐与80 m桩土储罐模型;计算刚性基础储罐和桩土储罐的地震响应、桩土储罐和纯土体情况下沿地基深度分布的最大加速度值并进行对比分析.结果考虑桩-土-储罐的相互作用后除晃动波高外,其他地震响应均有不同程度的减小;长周期地震动的场地放大效应小于短周期地震动,而频谱特性复杂且具有多峰性的地震动场地放大效应最大;纯土体的场地放大效应小于有上部结构的场地放大效应.结论地震动沿土体传播具有放大效应,上部结构的存在会增大放大效果,且按照刚性地基标准设计LNG储罐可以保证其安全性.     

非基岩场地核电厂CAP1400结构地震反应分析

针对核电工程的新型核岛结构CAP1400,建立屏蔽厂房和辅助厂房结构的整体有限元模型,进行模态分析获取了核岛结构的振动模态.进一步采用有限元模拟非基岩场地,考虑岩土与结构相互作用,针对不同的地震动情况开展不同剪切波速岩土场地上核岛结构的地震反应分析.研究表明:非基岩场地使核岛结构基础处的实际地震动输入有显著的改变,随着场地岩土剪切波速的增加,核岛结构基础处反应的加速度和应力增大,而位移及加速度反应谱峰值所对应的周期值减小.建议核岛结构抗震设计中非基岩场地导致的土-结相互作用影响应予以考虑,但当场地岩土剪切波速值大于1 250m/s时,其影响可以忽略.     

深软场地地铁地下车站结构近、远场地震反应数值分析

场地条件和地震动特性对地铁地下车站结构地震反应有重要影响,为了研究深软场地地铁地下车站结构近、远场地震反应特性,以苏州地铁一号线星海站为工程背景,基于苏州地震构造环境,建立深软地基-地铁车站结构二维非线性静动力耦合有限元分析模型,对深软场地地铁地下车站结构在近场中强震和远场强地震作用下的地震反应特性进行了数值模拟分析,得到了2种地震动作用下车站结构加速度、变形、应力反应规律和损伤特性的差异。     

河漫滩-阶地复合地形场地的非线性地震反应特征

以滁州市地震小区划场地为原型,针对由河漫滩、阶地、波状起伏的低丘等组成的典型复合场地,基于ABAQUS软件显式有限元并行计算平台,建立了大尺度场地二维模型,考虑土体的非线性特征,以SH波作为输入地震动,分析了河漫滩-阶地复合场地地震动力响应特征.结果表明,(1)与基岩地震动峰值加速度相比,土层近地表范围内(15m以浅)峰值加速度均表现出明显的放大现象,15m以深土层地震动放大效应随深度增加而逐渐减弱,且随深度增大,PGA放大系数值逐渐小于1.0;(2)土层峰值加速度随着深度增加非单一递减,局部土层深度地震动出现聚集效应,这一现象在河漫滩区表现比较明显;(3)场地不同区域地震动放大效应差异较大,河漫滩区地震动放大效应要明显比阶地低丘区更大;且输入地震动峰值相同时,河漫滩区反应谱特征周期要大于阶地区域,两者差距达0.05—0.15s;(4)随着输入地震动增加,反应谱谱峰向长周期方向移动明显.     

不同类别场地大型异跨地铁地下车站结构地震反应分析

场地类别对地下结构的地震反应具有重要影响,随着地下结构横截面尺寸及其复杂程度的增加,这一影响将愈发显著.针对现有异跨地铁车站结构的特殊性,以苏州地铁工程建设为背景,通过对不同类别场地土-异跨地铁车站相互作用的120个静动耦合整体有限元数值模型结果进行分析,研究了场地类别和地震动特性对此类复杂截面地下结构地震反应的影响规...     

双线地铁隧道对三维非线性场地地表地震反应的影响

地铁隧道的存在破坏了原有场地的完整性,进而在地震来临时影响场地的地震反应。为探讨双线地铁隧道建成后对场地地表水平地震动的影响,针对北京某一典型双线地铁隧道工程场地,建立三维非线性场地模型。采用自由场边界和应力时程地震波输入方式,运用有限差分数值分析软件FLAC~(3D)进行模型计算,分析了双线地铁隧道对三维非线性场地地表地震反应的影响。结果表明:1双线地铁隧道的存在使隧道附近场地地表地震动峰值加速度呈现先增大后减小并趋于自由场的趋势;2双线地铁隧道的存在主要影响场地加速度反应谱的短周期部分;3入射地震动频谱对双线地铁隧道的场地地震反应有着显著的影响。文中得出的影响规律,为双线地铁隧道附近场地的设计地震动参数确定提供参考依据。     

地震动速度脉冲对大跨斜拉桥减震控制的影响

地震动的速度脉冲特性是加重工程结构在地震中的破坏程度的重要因素,速度脉冲已成为近断层地震动的重要工程特性之一.以一座大跨飘浮体系斜拉桥为例,选择了4组具有速度脉冲特性的实际地震动加速度记录及人工模拟的具有相同加速度反应谱而无速度脉冲的地震动时程分别作为地震动输入,利用三维有限元方法计算了地震动的速度脉冲对斜拉桥地震反应和减震控制反应,分析了地震动速度脉冲对斜拉桥地震反应和减震控制效果的影响特征.总体上看,斜拉桥在速度脉冲型地震动作用下的地震反应大部分要大于无速度脉冲型地震动的,近断层地震动的速度脉冲对斜拉桥无控制、半主动控制和被动控制地震反应均具有一定的不利影响,且地震动的速度脉冲对半主动控制和被动控制减震效果的影响趋势大体相同.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the