Winkler地基梁在温度场中受简谐激励的1/3次亚谐共振分析

研究W inkler地基梁在温度场中受简谐激励作用的1/3次亚谐共振问题。应用弹性理论和Galerk in方法建立W inkler地基梁在温度场中受简谐激励作用的非线性动力方程,根据非线性振动的多尺度法求得系统满足1/3次亚谐共振情况的一次近似解,并对其进行数值计算,分析了温度、调谐值、激励、阻尼、地基刚度等参数对系统的影响。     

A comparative study between China and U.S. on seismic design philosophy and practice of a long span arch bridge

This paper presents the first of a series of case studies on the seismic design of long span bridges （cable-stayed bridges, suspension bridges and arch bridges） under a cooperative research project on seismic behavior and design of highway bridges between the State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University and the Multidisciplinary Center for Earthquake Engineering Research, University at Buffalo. The objective of this series of case studies is to examine the differences and similarities on the seismic design practice of long span bridges in China and the U.S., to identify research needs and to develop design guidelines beneficial to bridge engineers in both countries. Unlike short to medium span bridges, long span bridges are not included in most seismic design specifications, mainly because they are location dependent and structurally unique. In this paper, an available model of a steel tied half through arch bridge with a main span of 550m in China is discussed. Analysis is focused on comparisons of the seismic responses due to different ground motions. Seismic design criteria and seismic performance requirements for long span bridges in both countries were first introduced and compared, and then three near field earthquake records with large vertical components were selected as the excitations to examine the seismic behavior and seismic vulnerability of the bridge. Results show that （1） the selected near field ground motions cause larger responses to key components （critical sections） of the bridge （such as arch rib ends） with a maximum increase of more than twice those caused by the site specific ground motions; （2） piers, longitudinal girders and arch crowns are more vulnerable to vertical motions, especially their axial forces; and （3） large vertical components of near field ground motions may not significantly affect the bridge＇s internal forces provided that their peak acceleration spectra ordinates only appear at periods of less than 0.2s. However, they may have more influence on the longitudinal displacements of sliding bearings due to their large displacement spectra ordinates at the fundamental period of the bridge.     

Kinematic source model for simulation of near-fault ground motion field using explicit finite element method

1 Introduction The prediction of broadband near-fault ground motion is an important aspect of seismic risk analysis, and is essential for the evaluation of urban seismic safety. Many methodologies are used to model the near-fault ground motions, such as the Green function method, ?nite element (FE) / ?nite difference (FD) method and a hybrid method (Aagaard, 1999; Oprsal and Zahradnik, 2002; Oprsal et al., 2003 a and b). In the hybrid method, the FE / FD method is used to model the low fr…     

储层结构控制下的开发响应特征初探--以双河油田为例

储层结构体现在层次性和拼合性2个方面.双河油田含油层段在地质层次上划分为10级:地层段、油层组、小层、单层、单砂体、成因砂体、成因增量、层系组、层系和纹层,体现了各级次的地质作用.拼合性体现为储层由不同的要素相互镶嵌叠置而成,其中较重要的是结构要素的规模及其空间匹配.基于储层的这种层次性和拼合性,形成了相应的储层剖面和平面预测模型,在区内划分出4类剖面模型样式和6类平面模型样式.不同的模型样式体现了不同的内部结构特征,而这种结构特征影响注水开发过程中的流体流动,进而形成不同的剩余油气分布样式.     

低级序复杂断块构造应力场定量模型与油气分布

在对现河低级序帚状断块构造体系研究的基础上,建立了沙一、东营及现今3期构造应力场定量模型,研究了构造应力场特征及其与油气分布的关系。研究表明,不同地质时期应力强度不同,应力的方向和大小都有变化,认为应力值由老到新呈增大趋势。最大水平主应力在平面上自帚状构造的撒开端向收敛端逐渐变低,在剖面上随深度增加而增加,断裂带是应力低值区,也是油气富集区。提出应力转换带为应力低值区,也是低幅断鼻构造的有利分布区,还是开发中后期复杂断块油藏剩余油富集区。      

印度-澳大利亚板块应力场数值模拟及其动力学分析

印度-澳大利亚板块的边界类型和性质十分复杂。本文采用伪三维有限元方法,利用WSM2000观测应力场数据的应力取向和应力状态作为主要约束,建立了印度-澳大利亚板块岩石层三维模型,对印度-澳大利亚板块构造应力场进行了数值模拟,进而探讨印度-澳大利亚板块所受边界力对板块内部应力场的影响。结果显示,印度-澳大利亚板块的构造应力场主要受到两个因素的控制:①软流层静压推力;②来自碰撞带的阻力,包括喜马拉雅、巴布亚新几内亚、新西兰和印度-澳大利亚板块与欧亚板块的西北边界。而来自俯冲消减带的拉张作用力对板内应力场的作用相对较小。      

安宁河-则木河断裂带地震视应力研究

利用四川和云南数字遥测地震台网的数字地震记录资料。研究了包括地震视应力在内的震源参数。首先对资料进行预处理,然后计算地动位移和速度的功率谱积分,再计算地震辐射能量和视应力等震源参数。根据计算结果分震级区间研究了视应力值沿安宁河-则木河断裂带的分布情况,及该断裂带上中等地震的震源谱及参数差异,认为安宁河断裂带视应力相对更高。     

华清4#泉水溶气体百分含量合计的强震远场前兆特征

华清4#泉水溶气体百分含量合计(QB)的取值范围为100±5.按4舍5入法取整数值,将其分为11个区段.以年为单位,统计QB落在每个区段内的频次.频率分布直方图显示,在QB取值区间内,分区段频率呈近似正态分布.将落入QB频率最高的区段称为轴,将轴在不同区段上位置的变化称为轴漂.研究表明,QB在不同区段上轴的漂移,反映了区域应力场的不同状态.轴落入99区段上,反映的是区域应力场的增强,与远场M≥7.0地震及伴生中强地震、鄂尔多斯块体周边后继中强地震有很好的相关性;轴落入98区段上,反映的是区域应力场的相对稳定;轴落入97区段上,反映的是巨大地震后,区域应力场的调整及中强地震活动格局的变化.文中还阐述了99区段轴值与地震对应关系的几个特征.     

盐津5.1级地震现场调查与烈度分布

对盐津5．1级地震现场38个居民点、20所学校、8个卫生院（室）及计生站、21项生命线工程及水利工程结构、文化旅游设施和铁路等的震害调查资料进行了分析,得出了本次地震的等烈度分布及有关参数。分析了场地条件、断层、震害异常原因及各类房屋、生命线工程、水利设施等的震害特征和地质灾害特点,并提出了灾区恢复重建的减灾措施和建议。     

龙首山几个镁铁-超镁铁质岩体比较

文章选择龙首山隆起区金川、塔马子沟、毛草泉、小口子、藏布台几个镁铁-超镁铁质岩体进行地质、地球化学比较研究,发现岩体普遍具有橄榄石堆晶特征,中段金川岩体以二辉橄榄岩为主要特征,外围岩体以单辉橄榄岩为特征.地球化学数据显示,这些镁铁-超镁铁质岩体处于相同的岩石系列,源区具有相似性,岩体含矿差异主要源自岩浆演化.结合地质综合场模型,提出金川外围岩体在龙首山隆起区,沿构造带东西长约80～100km范围存在金川深部岩浆房响应的产物.