System reliability considerations in probabilistic risk assesment of nuclear power plants

The frequencies and consequences of severe accidents at nuclear power plants are examined using a systematic procedure called probabilistic risk assessment (PRA). These accidents may be initiated by equipment malfunctions, operator errors or external initiators such as earthquakes, floods and tornadoes. It is in the case of the external events that the structural system reliability concepts are utilized. Taking the seismic risk analysis as an example, this paper discusses the different elements of the analysis — hazard analysis, fragility evaluation, systems analysis and risk quantification — and examines how the structural system reliability methods are applied. Areas requiring further investigation by the PRA analysts are indicated and the data and research needs are identified.     

Structural reliability and error control in reinforced concrete design and construction

Available statistical data suggest that human error in design and construction causes a significant proportion of performance failures; namely, structural failure, cost overruns and delays. A Human Reliability Analysis (HRA) model has been developed to simulate the effect of human error on the design and construction of a reinforced concrete beam. The proposed HRA model incorporates the effect of designer checking, independent design checking, engineering inspections of construction works, and interaction between the designer and contractor. Human performance models are described for all design and construction microtasks. It was found that human error leads to a significant loss of structural safety, but that error control measures (particularly design checking) significantly reduce this loss. It was also shown that construction errors are more detrimental to structural safety and are more difficult to detect and correct.     

增量动力分析方法的改进及其在高层混合结构地震危害性评估中的应用

在基于性能的地震工程中,增量动力分析(IDA)常被用于计算结构的动力反应、损伤性能及可能的经济损失。这种定量的危险性分析方法主要包括:选择一组地震波并完成结构非线性模型的IDA,总结得到各种分位值对应的IDA曲线及相关状态性能限值,将IDA结果与地震危险性分析结果结合起来形成结构地震危害性评估的计算格式。本文介绍了IDA的基本原理与过程,提出了改进IDA曲线统计的方法。通过对一栋25层高层混合结构进行IDA分析,得到该结构概率分位值为16%,50%和84%的IDA曲线及其对应的极限状态值,结合上海市概率地震危险性分析曲线,对该高层混合结构的地震危害性进行评估,同时对这种评估方法在高层混合结构中应用的可靠性与可行性进行论证。     

工程施工风险评估及管理

介绍了工程施工风险的特点,对各种风险进行了分类。分析了施工风险评估过程中对风险率、风险等级和风险量的确定方法,总结比较了多种常用风险评估方法的原理及特点。最后对施工风险管理实施步骤进行了说明。分析表明,工程施工风险的评估与管理对现代工程管理至关重要,在一定程度上决定了施工目标能否顺利实现。     

A method for determining fire accidental loads and its application to thermal response analysis for optimal design of offshore thin-walled structures

More than 70% of accidents that occur on offshore installations stem from hydrocarbon fire and explosion, and as they involve heat and blast effects, they are extremely hazardous with serious consequences in terms of human health, structural safety and the surrounding environment. To prevent further accidents, substantial effort has been directed towards the management of fire and explosion in the safety design of offshore installations. The aim of this paper is to present a risk-based methodology procedure to help determine the fire accidental design load of an offshore installation (AL Living Quarter) in association with the thermal response characteristics for structural optimisation. A probabilistic sampling approach with numerical fire simulations was taken to determine the fire accidental load. To determine the optimisation of the thin-walled structures of the living quarter, an A60 based on the results of thermal response analyses was conducted and the temperature distribution calculated. The analysis results suggest incorporating both the design and safety planning aspects of offshore Living Quarter.     

车站明挖深基坑拆撑后围护结构稳定性分析

通过对北京地铁奥体中心站明挖深基坑变形规律的分析,从计算目的、计算原理、桩断面的计算等探讨了拆撑风险,以制定有效的预防措施,从而保证结构的整体受力,尽量消除现场施工误差影响。     

园林要素防雷风险评估探讨

针对主要园林防雷要素,建议将园林要素的重要性、人的因素、年预计雷击次数、自身结构、内部环境和结构变化、外部环境和其他因素、雷击史七个方面作为园林要素防雷风险评估的主控项目,且区分不同要素的评估计算方法,并提出园林要素防雷等级按风险评估计算E值可分为五类。     

Cyclone damage and temporal changes to building vulnerability and economic risks for residential construction

A risk analysis procedure is developed to predict economic risks due to changes to existing housing vulnerability over time. The wind hazard and building vulnerability models are based on exposure of residential construction to cyclones in North Queensland, Australia. A feature of the building vulnerability model is that it includes the effect of enhanced (post-1980) building standards in North Queensland. A cyclone damage risk-cost-benefit analysis is then used to assess the economic viability of strengthening existing houses to post-1980 construction quality for temporal changes in economic risks for two scenarios: (i) retrofitting pre-1980 houses to post-1980 quality immediately after they experience cyclone damage, or (ii) rate of growth of the proportion of post-1980 construction. The cost of retrofit or additional cost of strengthened construction can be included in the risk analysis to help assess the economic viability of these and other scenarios. Results are given in terms of annual and annualised economic risks and the damage loss conditional on occurrence of an Average Recurrence Interval event. The annualised economic risk is a time-variant measure of risk that is influenced by temporal changes in building vulnerability, which can be used to help determine the time when a particular strengthening strategy will be economically viable. “Zones of economic viability” determine the potential for cost-effective retrofitting of residential construction. The risk analysis also enabled the time to economic viability to be calculated.     

A HUMAN RELIABILITY ANALYSIS OF REINFORCED CONCRETE BEAM CONSTRUCTION

A significant proportion of performance failures (e.g., structural failure, cost overruns, delays) are due to human error in the construction of in-situ reinforced concrete elements. A Human Reliability Analysis (HRA) model has been developed to simulate the effect of human error on the construction of a reinforced concrete beam. The proposed HRA model incorporates the effect of (i) initial errors (i.e., before engineering inspections) and (ii) errors remaining after engineering inspections. The following typical construction tasks are considered: number and size of reinforcing bars, effective depth of steel reinforcing, beam width, and quality of concrete mix. Human performance models are described for each of these microtasks. It was found that human error leads to a significant loss of structural safety. It was also shown that engineering inspections significantly increased structural reliability, but the resulting structural reliability was still an order of magnitude lower than "nominal" estimates of structural reliability.     

国家体育场钢结构施工过程模拟分析

简要介绍了在国家体育场设计中确定大跨度钢结构安装方案的原则、临时支撑塔架布置与主要安装步骤,采用逐次“激活”单元技术对钢结构安装过程进行模拟计算。计算分析表明,施工顺序对构件的内力与变形有显著的影响。通过对构件安装顺序的调整,可以达到结构优化、降低用钢量、加快施工进度的目的。对临时支撑塔架反力与钢结构卸载变形量进行了估算,并对安装误差产生的原因、肩部与顶面次结构后装引起结构几何构型的变化情况进行了详细的分析,提出钢结构安装的技术要点。     

2008奥运场馆建设风险管理工具——风险表的建立

2008北京奥运场馆建设风险管理系统包括两部分:风险管理的工具和风险管理的工作框架。风险管理工具包括风险表(RiskRegister)和项目风险预警系统;工作框架主要包括风险管理的工作流程和相应的组织机构。着重介绍已经完成的有关风险表的工作,明确定义2008奥运场馆建设目标,进行风险识别,并从识别出的242个风险因素中选取112个重要风险因素,建立风险分解结构,对44个直接风险因素制定处置措施,并明确风险管理责任单位,形成奥运场馆建设风险表。     

Risk analysis of bridge falsework cuplok systems

Bridge falsework systems are one of the most common temporary structures used to support the formwork during the construction of concrete bridges. In this paper, the development of a risk analysis of selected bridge falsework structures using the Cuplok^® system is presented by means of a risk-informed structural design methodology based on newly developed structural robustness and structural fragility indices. Illustrative examples are given detailing the steps and calculations needed, including consideration of model and statistical uncertainties, and the results obtained are discussed. Furthermore, strategies for decreasing risks are presented and risks are determined for a reference (baseline) scenario and one selected alternative (improved) scenario and later evaluated against proper risk criteria. For the cases analysed, it is concluded that if the cost of the permanent structure considerably exceeds the cost of the temporary structure, which is often the case, the extent of improvements in terms of structural and economical risks may justify the extra costs incurred by implementing simple quality management procedures.     

基于故障树和贝叶斯网络的仓储类建筑火灾风险评估

以降低仓储类建筑火灾风险为目的,通过分析影响仓储类建筑火灾发生原因,分析顶层事件与基层事件之间自上而下的因果关系,建立故障树,并将其映射到贝叶斯网络中,通过计算得出事件发生的先验和后验概率,并将两者有效的联系起来。给出各事件发生的重要度指标有结构指标、概率指标和关键指标,分别进行定量分析指出仓储类建筑最有可能存在的风险。文章以2010—2020年十年期间仓储类建筑火灾发生案例为样本对本文提出的模型进行验证。检验结果:文章提出贝叶斯网络模型能够有效评估仓储类建筑风险等级并降低火灾事故发生。     

A GIS-based human health risk assessment for urban green space planning—An example from Grugliasco (Italy)

The need to develop approaches for risk-based management of soil contamination, as well as the integration of the assessment of the human health risk (HHR) due to the soil contamination in the urban planning procedures has been the subject of recent attention of scientific literature and policy makers. The spatial analysis of environmental data offers multiple advantages for studying soil contamination and HHR assessment, facilitating the decision making process. The aim of this study was to explore the possibilities and benefits of spatial implementation of a quantitative HHR assessment methodology for a planning case in a typical urban environment where the soil is contaminated. The study area is located in the city of Grugliasco a part of the Turin (Italy) metropolitan area.The soils data were derived from a site specific soil survey and the land-use data from secondary sources. In the first step the soil contamination data were geo-statistically analysed and a spatial soil contamination data risk modelling procedure designed. In order to spatially assess the HHR computer routines were developed using GIS raster tools. The risk was evaluated for several different land uses for the planned naturalistic park area.The HHR assessment indicated that the contamination of soils with heavy metals in the area is not sufficient to induce considerable health problems due to typical human behaviour within the variety of urban land uses. An exception is the possibility of direct ingestion of contaminated soil which commonly occurs in playgrounds.The HHR evaluation in a planning case in the Grugliasco Municipality confirms the suitability of the selected planning option. The construction of the naturalistic park presents one solution for reducing the impacts of soil contamination on the health of citizens. The spatial HHR evaluation using GIS techniques is a diagnostic procedure for assessing the impacts of urban soil contamination, with which one can verify planning options, and provides an important step in the integration of human health protection within urban planning procedures.     

极罕遇地震作用下建筑结构一致风险抗倒塌设计方法研究

结合当前国际上以“抗倒塌”为目标进行地震动参数区划和以“一致倒塌风险”为设防目标进行结构抗震设计的发展趋势,针对我国现行建筑抗震设计规范体系中抗倒塌能力评估的局限性,建议了四种一致风险抗倒塌设计方法,详细介绍了四种方法的评价指标与计算过程。考虑极罕遇地震作用,基于极罕遇地震一致风险谱对地震动记录进行了挑选与调幅。以RC框-剪结构作为典型案例,采用四种抗倒塌设计方法进行验算,结果表明：同时考虑地震危险性与结构不确定性影响的全概率方法验算未通过,其余验算方法均通过,这说明了忽略结构所在场地危险性影响会造成结构倒塌性能评估的不准确性,未考虑结构体系多种不确定性影响会高估结构的抗倒塌性能,因此有必要推行“一致风险”的结构设计理念。     

Recording duration of ambient vibration monitoring for system identification of tall telecommunication towers

It is necessary to have reliable field measurement records for estimation of dynamic characteristics. Increasing duration of the record is one of the common methods for reduction of such errors in the results. Dynamic characteristics of telecommunication towers in higher modes are important for designers, but these parameters could be obtained from ambient vibration monitoring during typhoons in which duration of vibration is not long enough for reducing measurement errors. This paper suggests a procedure for obtaining the duration of recording time for more reliable determination of structural characteristics of telecommunication towers. It is suggested to record the vibration of towers in the form of a set of long‐term and short‐term duration recordings for lower and higher modes, respectively. This procedure was verified with field measurement of Milad telecommunication tower. The results show that natural frequencies determined by this procedure are in good agreement with finite element model analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Statistical distributions of health risks

This study deals with the imprecision associated with estimating the risk of health effects due to environmental causes. The major thrust revolves around the notion that the calculation of statistical risk, itself a probability, contains significant imprecision because of the cascade of error through the computations on which the risk, or probability of contracting a disease, is based. The cascade or risk is an old problem in mathematics and physics, and the conventional issues involving round-off, truncation and related measurement errors are not discussed here. The potential inadequacy of the model by which risk is calculated, the inherent variability in the stochastic processes by which the disease mechanism or initiator is transported down-gradient, and the variability inherent in varying levels of human sensitivity are of more concern. These all conspire to develop a distribution of risk rather than a scalar value, and policy-makers must deal with this distribution in a rational and consistent way. Some suggestions are offered for managing this problem.     

A rational quantitative optimal approach to dam safety risk reduction

The rational quantitative optimal (RQO) approach presents a robust risk evaluation model which produces a definitive result for the reduction of risk from overtopping of earth-fill dams. The model is based on principles of risk, but an analysis of a portfolio of dams provides discrete optimal results, not expressed in terms of probability. All the steps that the methodology comprises have been developed exhaustively and propose to address concerns raised by dam owners and decision-makers regarding risk-based dam safety: a transparent framework for decision-making related to public safety, which will also appeal to the technically minded portfolio manager looking for a purely quantitative procedure to assist in the decision-making process. The RQO process is applied mechanistically, not requiring judgement from the decision-maker. In so doing it addresses the concern raised by dam owners regarding the judgmental probability of risk assessment. Risk in this paper is associated with embankment dams and external erosion, which is the single largest cause of failure of these dams. Also, in the context of this article, ‘optimal' refers to maximising lives saved over a portfolio of dams under the constraint of limited resources.     

Proposal of a probabilistic model for multi-hazard risk assessment of structures in seismic zones subjected to blast for the limit state of collapse

It is desirable to verify the structural performance based on a multi-hazard approach, taking into account the critical actions the structure in question could be subjected to during its lifetime. This study presents a proposal for a probabilistic model for multi-hazard risk associated with the limit state of collapse for a reinforced concrete (RC) structure subjected to blast threats in the presence of seismic risk. The annual risk of structural collapse is calculated taking into account both the collapse caused by an earthquake event and the blast-induced progressive collapse. The blast fragility is calculated using a simulation procedure for generating possible blast configurations, and verifying the structural stability under gravity loading of the damaged structure, using a kinematic plastic limit analysis. As a case study, the blast and seismic fragilities of a generic four-storey RC building located in seismic zone are calculated and implemented in the framework of a multi-hazard procedure, leading to the evaluation of the annual risk of collapse.     

State-of-the-Art in the Measurement of Volatile Organic Compounds Emitted from Building Products: Results of European Interlaboratory Comparison

Abstract Eighteen laboratories from 10 European countries participated in a comparison organized as part of the VOCEM project, a 2.5-year research collaboration among 4 research institutes and 4 industrial companies. The scope of the project was to improve the procedure used to measure volatile organic compounds (VOC) emitted from building materials and products in small test chambers. The interlaboratory comparison included the GC-MS determination of 5 target compounds from carpet, 8 from polyvinyl chloride (PVC) cushion vinyl and 2 from paint; for the first time, chamber recovery (sinks), homogeneity of solid materials and possible contamination during transport were tested. The results show that the intralaboratory variance (random errors) is much smaller than the interlaboratory variance (systematic errors). Causes of the largest interlaboratory discrepancies were: (i) analytical errors; (ii) losses of the heaviest compounds due to sorption on the chamber walls; and (iii) non homogeneity of the materials. The output of this work concerns both the objective of labelling materials with regard to their VOC emissions and the pre-standard drafted by the European Commitee for Standardization (CEN) for this type of determination.