基于网络效率的城市轨道交通网络震后性能评估∗

对于以地铁为主要组成部分的城市轨道交通系统,地震作用造成的车站、隧道等结构的损伤和破坏,会严重影响系统的交通运行功能。目前针对扰动事故场景下轨道交通网络性能的研究,主要集中于随机失效和蓄意攻击场景,缺乏地震场景下的相关研究。本文采用客流加权的网络效率指标,研究了不同地震作用下轨道交通网络的抗震性能。利用图论建模方法构建网络拓扑模型,基于车站、区间隧道等主体结构的地震易损性模型计算结构失效概率,采用 Monte Carlo 模拟方法抽样网络单元的震后状态,利用三类网络效率指标(拓扑网络效率、站点流量加权网络效率和网络服务效率)评价网络的震后性能。以北京市轨道交通网络为例,比较了不同地震作用场景下的网络性能指标,选择站点流量加权网络效率指标表示网络震后性能;计算不同 PGA 下的网络性能损失,拟合得到了案例轨道交通网络地震易损性模型,便于案例网络震后性能的快速评估。     

工作竖井与隧道连接处支护结构横向地震响应

建立了工作竖井与盾构隧道、明挖隧道相连的空间交叉结构三维模型,采用FLAC3D对该复杂结构进行了横向地震响应分析,得到了工作竖井与隧道连接处支护结构关键点的位移和应力响应规律。通过对地震横向激励过程中竖井与隧道连接处支护结构收敛位移和关键点主应力峰值的分析,对该结构的横向抗震性能做出了评价。     

桥梁群体震害预测方法的研究

本文研究了桥梁群体震害预测方法的理论,并采用模糊数学、灰色系统理论和概率分析方法,建立了中、小型桥梁群体震害预测的数学模型。在对江南一带城市地震震害预测工作中桥梁抽样单体震害预测经验法的计算基础上,给出了公路桥梁在不同地震烈度影响下的单因素评价矩阵,为区域性的地震震害预测工作提供了一个有力的实用工具。     

杭州过江隧道火灾时人员安全疏散研究

以杭州过江隧道为研究对象,分析了隧道火灾时人员安全疏散准则及影响因素,介绍了隧道内人员安全疏散研究的一种思路和方法。设定包含最不利情况的火灾场景,然后对各种火灾场景下的烟气蔓延及人员疏散进行模拟,得到了各种火灾场景下隧道内的可用安全疏散时间ASET曲线和必需安全疏散时间RSET曲线;比较分析这两条曲线,得到了疏散救援通道的设置参数,给隧道消防设计提供了依据。     

基于修正惯用法的埋深对圆形隧道地震反应影响∗

采用修正惯用法,在考虑土拱效应对圆形隧道结构受力状态影响的基础上,研究了埋深对地下结构地震反应的影响规律。首先,对比分析了不考虑和考虑土拱效应时、地震荷载作用前,隧道结构内力分布及随埋深的变化规律;将作用于隧道结构上的水平地震荷载等效为围岩土体变形导致的土压力的改变值;继而探讨了考虑土拱效应后,地震荷载引起的隧道结构内力的改变,研究了不同地震动强度下,埋深对圆形隧道结构地震反应的影响规律。 研究结果显示,地震作用下,圆形隧道结构的内力随着埋置深度的增加呈现出先增大后减小或趋于稳定的趋势,即圆形隧道结构地震反应存在一个抗震关键埋深。     

饱和土-隧道动力相互作用对地震动土作用和孔隙动水压力的影响

本文利用间接边界元方法,研究了饱和土-隧道动力相互作用对隧道地震动土作用和孔隙动水压力的影响,考虑了不同隧道质量和埋深,以及地震波斜入射情况。饱和场地根据Biot理论模拟为两相介质,通过将饱和两相介质模型所得隧道地震动土作用与单相介质模型结果进行比较,分析了饱和土骨架和孔隙水动力耦合作用的影响。结果表明,饱和土-隧道动力相互作用对地震动土作用有明显放大效应,本文算例中,隧道水平地震动土作用较自由场结果最大放大1. 7倍,竖向地震动土作用较自由场结果最大放大1. 6倍;饱和土骨架和孔隙水的动力耦合作用对隧道地震动土作用大小也有显著影响,本文算例中,单相介质模型所得地震动土作用较饱和两相模型的最大差别可达210%。     

软土地区地表结构对盾构隧道地震响应影响的风险分析

本文基于ABAQUS有限元软件建立了软土地区地表结构-土-隧道相互作用的非线性有限元模型,地表结构采用置于刚性筏板基础的单自由度体系模拟。考虑地表结构的有无,不同的土体模型及地震荷载,通过水平地震作用下的动力时程反应分析,研究了地表结构对盾构隧道周围土体以及衬砌地震响应的影响。研究表明,地表结构的存在会增大隧道周围土体地震响应,从而引起隧道结构变形以及动态内力的显著增加,同时发现采用弹塑性分析下的隧道地震响应大于采用黏弹性分析。因此,地表结构作用是影响盾构隧道响应的重要因素,综合分析地表结构-土-隧道作用下的结构动态响应有助于更合理的预测地震荷载下盾构隧道结构安全风险。     

下穿隧道对地铁车站结构地震反应的影响研究*

针对下穿隧道对临近地铁车站地震反应的影响问题,本文采用数值模拟方法,基于 ABAQUS 平台建立了隧道下穿大开地铁车站的整体三维非线性数值分析模型,通过改变地震动类型和隧道与车站结构的交叉净距,从结构构件的破坏比和竖向变形等角度,定量分析了不同工况下隧道下穿对车站结构地震反应的影响,并与单体大开车站原型结构的地震反应进行了对比。研究表明：下穿隧道会增大地铁车站结构中柱和侧墙的破坏比(相应的最大增幅：中柱为 35%,侧墙为 26%);同时,底板的竖向变形显著增大,最大增幅达到 100%;随着交叉净距的增大, 中柱和侧墙地震反应减小,而底板竖向沉降有所增大;下穿隧道对车站结构地震反应的影响范围约为隧道直径的 3 倍。研究成果对隧道近距离穿越地铁车站结构的设计与分析具有一定的参考价值。     

随机地震作用下悬浮隧道锚索的动力响应分析∗

研究了悬浮隧道锚索在地震与水动力共同作用下的动力响应。通过将悬浮隧道锚索简化为欧拉梁模型,建立悬浮隧道锚索受到水动力和地震共同作用振动的运动方程。采用分离变量法和伽辽金法求解运动方程,并使用四阶龙格-库塔法求解得到悬浮隧道锚索的位移响应情况。采用三角级数法模拟生成人工地震波,并选用了三种著名的地震记录,对悬浮隧道在不同地震波激励下的关键结构参数对锚索位移响应进行数值分析。结果表明:(1)地震的加速度越大,锚索的运动响应越剧烈,产生的位移和能量越大。地震波的峰值加速度出现时间和大小也对锚索的峰值振幅有一定影响。(2)参数频率和阻尼比等因素对锚索的位移都有重要的影响,但在不同的地震作用下影响程度不同。通过控制参数频率和阻尼比可以减小地震对悬浮隧道锚索及整体结构的破坏效果。     

大跨径预应力混凝土连续梁桥地震反应分析

大跨连续梁桥纵向延伸较长,地震发生时各个支承处的地震波的振幅和频率是不同的.以某12跨预应力混凝土连续梁桥为例,推导了结构的运动方程,采用有限元结构分析软件ANSYS建立了该桥的动力分析模型,进行了模态分析和时程分析.通过输入不同波速的地震波,计算行波激励下桥梁的地震反应,并和一致激励下的结果进行对比,分析了行波效应对桥梁地震反应的影响.结果表明:滑动支座摩擦力减小了桥梁纵向的地震反应,但对桥梁横向地震反应影响较小.行波效应减小了制动墩的纵向地震反应,增大了其它桥墩的纵向地震反应,但对桥梁横向地震反应影响较小.     

Cholera in Sudan: An account of an epidemic in a refugee camp in eastern Sudan, May-June 1985

In 1985 cholera has been a serious problem in the horn of Africa, particularly affecting the many famine victims and refugees in that region. In this paper the history of cholera in Africa is briefly summarized, as is the background to the current refugee situation in eastern Sudan. A cholera epidemic involving 1,175 cases in two adjacent refugee camps in eastern Sudan is described. In this epidemic there were thirteen inpatient deaths and thirty-eight known home deaths from cholera. The management of the epidemic is described in detail. Overall an average of 8 1. of intravenous fluid was used per case, a higher figure than was anticipated, probably because of the unexpected degree of vomiting and the shortage of trained nursing staff.
The relationship between cholera and malnutrition is explored and hypochlorhydria is suggested as the main reason for the increased susceptibility to cholera among malnourished populations. It was observed that severely malnourished adults and children appeared to nave less severe diarrhoea with their cholera, presumably because of reduced mucosal surface area and poor enterocyte function. Finally possible means of aborting cholera epidemics are discussed.     

A retrospective statistical review of deaths owing to migration through the southeasternmost land borders of the European Union,Greece 2000–14

The land borders of Evros, Greece, have been a common entry point for undocumented migrants on their way to Europe through Turkey. Adverse conditions, however, have resulted in many human casualties over the years. On the Greek side, 334 cadavers were retrieved between 2000 and 2014. This study provides a detailed forensic account of the humanitarian disaster in Evros to create an official scientific record of the situation. It showcases the gravity of the global issue of migration relating to health and mortality, and encourages communication and continual improvement of the approach and patterns of practices surrounding the subject. A retrospective statistical research review was conducted of border‐related fatalities between 2000 and 2014, assessing the age and gender of victims, the cause of death, the location of bodies, identification rates, and country of origin. Age ranged generally from 24 to 29 years, but infants and children were among the deceased.     

Complexity,continuity and change: livelihood resilience in the Darfur region of Sudan

Darfur farming and pastoralist livelihoods are both adaptations to the environmental variability that characterises the region. This article describes this adaptation and the longer‐term transformation of these specialised livelihoods from the perspective of local communities. Over several decades farmers and herders have experienced a continuous stream of climate, conflict and other shocks, which, combined with wider processes of change, have transformed livelihoods and undermined livelihood institutions. Their well‐rehearsed specialist strategies are now combined with new strategies to cope. These responses help people get by in the short term but risk antagonising not only their specialist strategies but also those of others. A combination of factors has undermined the former integration between farming and pastoralism and their livelihood institutions. Efforts to build resilience in similar contexts must take a long‐term view of livelihood adaptation as a specialisation, and consider the implications of new strategies for the continuity and integration of livelihood specialisations.     

The cultural politics of mining and natural disaster in Indonesia: by fire and sword

Natural disasters are inevitably the outcome of cultural agonisms. The cultural politics of natural disasters are shaped by competing claims and conceptions of ‘nature’. Recent disasters in Indonesia are directly linked to these contending conceptions and the ways in which different social groups imagine risk and reward. The Sidoarjo volcanic mudflow of 2006 represents a volatile and violent exemplar of contending cultural and economic claims. Like other disasters in Indonesia and elsewhere in the developing world, this ‘natural’ disaster is characterised by differing conceptions of ‘nature’ as cultural tradition, divine force, and natural resource. A new extractive project in East Java is exhibiting similar economic and cultural agonisms, particularly around the notion of development, environment, self‐determination, and tradition. This paper examines the ‘disputes over meaning’ associated with natural disasters in contemporary societies, and the ways in which they are related to human culture, social organisation, and hierarchical systems of violence.     

Reflections on 40 years of Disasters, 1977–2017

This reflection, based on a keynote address to celebrate the fortieth anniversary of Disasters on 14 September 2017, begins by considering some of the prevailing assumptions that existed at the time of the journal's creation. Next is a summary of significant milestones during the past 40 years, covering major global trends, changing disaster impacts, and key developments in disaster risk management. Contrasting approaches in the first and fourth decade of the journal's history are then followed by examples of changes in terminology in the disaster field as an indication of shifting values. The paper goes on to explore the context of 2017, with observations of problem areas such as the loss of knowledge, failures to tackle the root causes of disasters, shortfalls in international assistance, and some negative attitudes. It closes by evaluating some current positive occurrences, including a reduction in casualties, sharing of experience, technological advances, and dramatic improvements in disaster warning.     

Fiji, land of tropical cyclones and hurricanes: A case study of agricultural rehabilitation

Tropical cyclones and hurricanes have a severe impact on the social and economic activities of affected communities. For small island nations in the Pacific region, the effects can be devastating because of their smallness. FQi and several other countries in the region are vulnerable to such disasters as they are situated in the zone where cyclones occur frequently.
During the last decade, the frequency of natural disasters and their adverse impact on die economic and social development of small nations like Fiji, has aroused awareness mat relief efforts must go beyond immediate "mopping up" operations to those which contribute to attaining longer term benefits through reconstruction and rehabilitation.
The paper outlines the 1985 agricultural rehabilitation program and discusses related issues and problems.     

Risk communication in emergency response to a simulated extreme flood

Risk communication in flood incident management can be improved through developing hydrometeorological and engineering models used as tools for communicating risk between scientists and emergency management professionals. A range of such models and tools was evaluated by participating flood emergency managers during a 4-day, real-time simulation of an extreme event in the Thamesmead area in the Thames estuary close to London, England. Emergency managers have different communication needs and value new tools differently, but the indications are that a range of new tools could be beneficial in flood incident management. Provided they are communicated large model uncertainties are not necessarily unwelcome among flood emergency managers. Even so they are cautious about sharing the ownership of weather and flood modelling uncertainties.     

Tsunami survivors' perspectives on vulnerability and vulnerability reduction: evidence from Koh Phi Phi Don and Khao Lak, Thailand

This paper presents the results of primary research with 40 survivors of the 2004 Indian Ocean tsunami in two communities: Khao Lak (n=20) and Koh Phi Phi Don (n=20), Thailand. It traces tsunami survivors' perceptions of vulnerability, determines whether residents felt that the tsunami affected different communities differently, identifies the populations and sub-community groups that survivors distinguished as being more vulnerable than others, highlights community-generated ideas about vulnerability reduction, and pinpoints a range of additional vulnerability reduction actions. Tsunami survivors most consistently identified the 'most vulnerable' community sub-populations as women, children, the elderly, foreigners, and the poor. In Khao Lak, however, respondents added 'Burmese migrants' to this list, whereas in Koh Phi Phi Don, they added 'Thai Muslims'. Results suggest that the two case study communities, both small, coastal, tourism-dominated communities no more than 100 kilometres apart, have differing vulnerable sub-groups and environmental vulnerabilities, requiring different post-disaster vulnerability reduction efforts.     

The ethical contours of research in crisis settings: five practical considerations for academic institutional review boards and researchers

The number of research studies in the humanitarian field is rising. It is imperative, therefore, that institutional review boards (IRBs) consider carefully the additional risks present in crisis contexts to ensure that the highest ethical standards are upheld. Ethical guidelines should represent better the specific issues inherent to research among populations grappling with armed conflict, disasters triggered by natural hazards, or health‐related emergencies. This paper seeks to describe five issues particular to humanitarian settings that IRBs should deliberate and on which they should provide recommendations to overcome associated challenges: staged reviews of protocols in acute emergencies; flexible reviews of modification requests; addressing violence and the traumatic experiences of participants; difficulties in attaining meaningful informed consent among populations dependent on aid; and ensuring reviews are knowledgeable of populations' needs. Considering these matters when reviewing protocols will yield more ethically sound research in humanitarian settings and hold researchers accountable to appropriate ethical standards.