Seismic reliability of V‐braced frames: Influence of design methodologies     

Alessandra Longo  Rosario Montuori  Vincenzo Piluso 《地震工程与结构动力学》2009,38(14):1587-1608

According to the most modern trend, performance‐based seismic design is aimed at the evaluation of the seismic structural reliability defined as the mean annual frequency (MAF) of exceeding a threshold level of damage, i.e. a limit state. The methodology for the evaluation of the MAF of exceeding a limit state is herein applied with reference to concentrically ‘V’‐braced steel frames designed according to different criteria. In particular, two design approaches are examined. The first approach corresponds to the provisions suggested by Eurocode 8 (prEN 1998—Eurocode 8: design of structures for earthquake resistance. Part 1: general rules, seismic actions and rules for buildings), while the second approach is based on a rigorous application of capacity design criteria aiming at the control of the failure mode (J. Earthquake Eng. 2008; 12 :1246–1266; J. Earthquake Eng. 2008; 12 :728–759). The aim of the presented work is to focus on the seismic reliability obtained through these design methodologies. The probabilistic performance evaluation is based on an appropriate combination of probabilistic seismic hazard analysis, probabilistic seismic demand analysis (PSDA) and probabilistic seismic capacity analysis. Regarding PSDA, nonlinear dynamic analyses have been carried out in order to obtain the parameters describing the probability distribution laws of demand, conditioned to given values of the earthquake intensity measure. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

全球地震、火山分布及其变化特征   总被引：2，自引：0，他引：2       下载免费PDF全文

洪汉净  陈会仙  赵谊  胡久常 《地震地质》2009,31(4):573

地震和火山都反映了地球表层的构造活动,因而地震活动区往往也是火山活动区。根据全球大震、火山活动目录,分析研究了全球地震、火山分布的特征。描述了各区的地震、火山活动分布,总结了地震、火山活动强度的时、空分布特征。全球地震、火山活动可以分为碰撞带、大陆区和大洋区。大陆地震以其片状的分散分布而不同于板块边缘的带状分布,大陆火山活动比大洋火山更受应力场的影响。大洋区地震活动相对较弱,岩浆活动主要是平静的岩浆溢出与洋中脊的扩张,往往没有形成火山喷发。有记录的火山喷发主要来自深部地幔的热柱。俯冲-碰撞活动区地震活动与火山喷发最强烈,大角度俯冲的弧后火山活动最强,当板块运动方向与板块边缘走向成小角度相交时,缺少正面俯冲的动力,火山活动相对平静。>500km深震的地段,火山活动较弱。火山与地震强烈活动的大多在大地水准面(Geoid)异常高的区域。地震与火山平均纬度随时间表现出同步的变化外,火山和大震活动也显示了大致同步的变化  相似文献   

全球化与全球变化关系研究     

田光进 《热带地理》2009,29(2)

全球化是本世纪人类社会发展的最重要特征之一,它不仅促进了产品和服务的流动,而且促进了劳动力、金融、资源及环境生产要素等的流动,技术的发展提高了生产效率和物质要素的可利用性.全球化扩大了人类活动的范围和影响程度,对人类社会、政治、文化、经济等各个方面都产生了影响,从而加深了全球环境变化.全球环境变化已经成为伞球化进程的重要方面,人类对全球环境变化的应对方式直接关系到人类的生存及可持续发展.全球化深化了国际分工,发达国家制造业大量向发展中国家转移,从而导致发展中国家承担了更多的环境污染,造成发展中国家碳排放增长较快.在全球化进程中,中国在享受初级产品大量出口并产生顺差的同时,也把环境污染输入进来,并把大量资源输出去,从而造成中国资源紧张和环境污染.随着中国经济实力的增强,中国的政治、文化等都会在全球产生更大影响,研究全球化进程对中国现代化进程的影响及中国现代化进程对全球化的影响、全球化进程与全球环境变化的关系具有重要的理论和实践意义.  相似文献   

全球变化对宁夏近40 a极端气温变化的影响   总被引：4，自引：1，他引：3  

赵光平  杨淑萍  穆建华  马力文  陈晓娟  周虎 《中国沙漠》2009,29(6):1207-1211

 对全球气候变暖背景下宁夏气候变化基本事实,利用近40多年来宁夏基本气象资料,对年平均气温、极端气温的变化进行了研究。结果表明,近40多年宁夏年平均气温呈连续上升趋势,1986年之后增温速率加快,增温幅度高于全国平均值;年极端最高气温、极端最低气温均在波动中持续上升,年极端最低气温上升幅度明显超过年极端最高气温;各季极端最高、极端最低气温呈非对称性变化,秋季各地极端最高气温增温幅度超过极端最低气温,但春夏冬三季极端最低气温增温远比极端最高气温明显,该特点在夏季表现得更突出;各月极端最高气温、极端最低气温均呈升温趋势。  相似文献   

Modelling for prediction of global deforestation based on the growth of human population   总被引：1，自引：0，他引：1  

Krishna Pahari  Shunji Murai 《ISPRS Journal of Photogrammetry and Remote Sensing》1999,54(5-6)

Deforestation due to ever-increasing activities of the growing human population has been an issue of major concern for the global environment. It has been especially serious in the last several decades in the developing countries. A population-deforestation model has been developed by the authors to relate the population density with the cumulative forest loss, which is defined and computed as the total forest loss until 1990 since prior to human civilisation. NOAA-AVHRR-based land cover map and the FAO forest statistics have been used for 1990 land cover. A simulated land cover map, based on climatic data, is used for computing the natural land cover before the human impacts. With the 1990 land cover map as base and using the projected population growth, predictions are then made for deforestation until 2025 and 2050 in both spatial and statistical forms.  相似文献   

CMIP5模式对中国地区气温模拟能力评估与预估   总被引：5，自引：0，他引：5  

张艳武  张莉  徐影 《气候变化研究进展》2016,12(1):10-19

利用第五次国际耦合模式比较计划（CMIP5）中29个气候模式的气温模拟结果,评估了各模式对中国地区年平均气温的模拟能力,对未来不同典型浓度路径（RCPs）下中国地区气温的可能变化给出了预估。结果表明：各模式能较好地模拟过去100多年中国地区增温趋势和年平均气温的空间分布,从模式间标准差来看,各模式对中国中部、南部气温模拟具有较高的一致性。利用相对均方根误差分析了各模式的模拟能力,对于多时间尺度（月、年）气温的气候平均态,有7个模式表现良好,高于中等水平,5个模式的模拟能力低于中等水平,模式集合平均值的模拟效果优于大多数单个模式。根据29个模式的评估结果,使用模拟性能相对较好的模式分析了未来不同排放情景下中国地区气温变化,21世纪前期,不同排放情景之间的预估结果差别较小,21世纪中期各情景之间的差别逐渐增大,到21世纪后期,3种排放情景的升温差别明显增大。  相似文献   

近地空间环境的GNSS无线电掩星探测技术   总被引：1，自引：1，他引：0       下载免费PDF全文

乐新安  郭英华  曾桢  万卫星 《地球物理学报》2016,59(4):1161-1188

从GPS/MET计划开始,基于GNSS的无线电掩星技术已成为一种强大的近地空间环境探测手段.截至到目前,已经有20多颗发射的低轨道卫星带GPS掩星接收机,其中COSMIC是首个专门用于掩星探测的卫星星座.这些掩星数据被广泛应用于气象预报、气候与全球变化研究、及空间天气监测和电离层研究.由于COSMIC的成功,相关合作单位目前正积极推动COSMIC-2计划,该计划将总共有12颗卫星,于2016年与2019年各发射6颗.COSMIC-2将携带一个高级的GNSS掩星接收机,它将接受GPS与GLONASS信号,并具备接受其他可获得信号源的能力(如中国北斗定位信号),其每日观测的掩星数量将是COSMIC的4~6倍.同时COSMIC-2还将携带两个空间天气载荷,加强空间天气的监测能力.本文以COSMIC与COSMIC-2计划为主线,对掩星的发展历史、技术要点进行了简单介绍,并简要综述了COSMIC取得的部分科学成果,同时对未来包括技术发展和众多的掩星观测进行了展望.  相似文献   

Development of deformable connection for earthquake‐resistant buildings to reduce floor accelerations and force responses          下载免费PDF全文

Georgios Tsampras  Richard Sause  Dichuan Zhang  Robert B. Fleischman  Jose I. Restrepo  David Mar  Joseph Maffei 《地震工程与结构动力学》2016,45(9):1473-1494

This paper presents the development of a deformable connection that is used to connect each floor system of the flexible gravity load resisting system (GLRS) with the stiff lateral force resisting system (LFRS) of an earthquake‐resistant building. It is shown that the deformable connection acts as a seismic response modification device, which limits the lateral forces transferred from each floor to the LFRS and allows relative motion between the GLRS and LFRS. In addition, the floor accelerations and the LFRS story shears related to the higher‐mode responses are reduced. The dispersion of peak responses is also significantly reduced. Numerical simulations of the earthquake response of a 12‐story reinforced concrete shear wall example building with deformable connections are used to define an approximate feasible design space for the deformable connection. The responses of the example building model with deformable connections and the example building model with rigid‐elastic connections are compared. Two configurations of the deformable connection are studied. In one configuration, a buckling restrained brace is used as the limited‐strength load‐carrying hysteretic component of the deformable connection, and in the other configuration, a friction device is used. Low damping laminated rubber bearings are used in both configurations to ensure the out‐of‐plane stability of the LFRS and to provide post‐elastic stiffness to the deformable connection. Important experimental results from full‐scale tests of the deformable connections are presented and used to calibrate numerical models of the connections. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Seismic assessment of damaged piloti‐type RC building subjected to successive earthquakes          下载免费PDF全文

Jiuk Shin  JunHee Kim  Kihak Lee 《地震工程与结构动力学》2014,43(11):1603-1619

Building structures damaged by a seismic event may be exposed to the risk of aftershocks or another event within a certain period. In this paper, the seismic assessment of damaged piloti‐type RC buildings was carried out to evaluate probabilistic retrofitting effects under successive earthquakes. First, a framework to evaluate the effectiveness of retrofitting was proposed, and then the proposed methodology was demonstrated with a structure retrofitted with buckling‐restrained braces (BRBs). For consideration of realistic successive earthquakes, past records measured at the same station were combined. Within the framework, a series of nonlinear time history analyses were performed for an as‐is model subjected to single earthquake, a damaged model subjected to successive earthquakes, and a damaged model retrofitted with BRBs subjected to successive earthquakes. In addition, fragility analysis was systematically applied in the framework for evaluation of effectiveness of the retrofitting strategy. The proposed framework was capable of quantifying the influence of successive earthquakes and evaluating the effectiveness of BRB retrofitting by considering the severity of the first earthquake damage and the hysteresis behavior of the retrofit element. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

壳体稳定性问题的研究进展     

安镇文  许绍燮  乔森  柴金梅 《地震地磁观测与研究》2014,(1):1-9

为探索大地震成因的物理机理,根据板壳理论的研究结果,综述多年来柔韧壳体非线性大挠度变形研究中与地震成因相关的壳体结构变形问题的研究进展、壳体结构变形过程中的稳定性问题。同时,介绍壳体曲率变化对其变形过程中稳定性的影响,期望能为探索大地震成因机理的研究提供某些有用的物理依据与理论基础。  相似文献