建筑物可靠性评价

探讨了现存建筑物可靠性评价的极限状态方法,提出荷载水平方法,建立了结构构件可靠性评价的极限状态准则。基于结构失效的机构理论,提出结构体系可靠性评价的“破损机构”方法,以使结构成为“破损机构”或“局部破损机构”的“破损截面”的最高等级作为结构体系可靠性评级。     

The impact of differences in reliability data on the results of probabilistic safety analyses

The lack of plant-specific reliability data for probabilistic safety assessments is occasionally used for discrediting and doubting the validity of such analyses. On the other hand, analyses are often performed without even discussing the applicability of generic reliability data. In an attempt of clarification the impact of several sets of reliability data stemming from different sources on the explosion frequency of two processes with exothermal reactions (one of them is analyzed with plant-specific data) are quoted. As a further case study the reactor cooling system of one of the processes is analyzed. Additionally, a procedure using frequency and probability ranges is employed for comparison. The results show agreement within their respective uncertainty bounds; the identification of key components for safety is not hampered by data differences. The superiority of plant-specific data, which should of course be acquired, cannot be doubted. Nevertheless, improving the safety of a plant is possible using probabilistic safety analyses even with data which do not stem from the plant under investigation.     

Improving safety and availability of complex systems using a risk-based failure assessment approach

This paper presents a structured risk-based failure assessment (RBFA) approach, which provides a complete solution to avoid repeated and potential failures to improve overall plant safety and availability. Technological advancements and high product demand have encouraged designers to design mega-capacity systems to enhance system utilization and improve revenues. However, these benefits make the systems more complex and thus prone to unnoticed failure. It is an overwhelming task to address all the failures due to the limited resources and time constraints. This leads to substandard and poor quality failure assessments, which cause repeated failures. To address this common industry concern, a four phase RBFA framework is proposed which is not limited to the identification of root cause(s) but also includes other actions such as failure monitoring. The four phases include the plan phase, the assessment phase, the analysis phase and the implementation-tracking phase. These phases cover identification of failure, failure analysis, root cause(s) analysis, and failure monitoring. In this paper, the applicability and advantages of the proposed approach are examined through two real case studies pertaining to bearing failure and drive coupling failure. By implementing the proposed approach, significant improvements have been experienced in the system availability in both the cases.     

A descriptive study of the OHS management auditing methods used by public sector organizations conducting audits of workplaces: Implications for audit reliability and validity

Past research has identified a research gap regarding studies of the reliability and validity of OHS management audit methods. This study describes 17 audit methods used by OHS auditing organizations in the broader public sector in the province of Ontario, emphasizing aspects relevant to audit reliability and validity. Wide variation was found in pertinent characteristics of the audit methods and in their corresponding programs. In addition, some discrepancies were found between actual auditing practices and international standards on management system auditing. Further research is needed to precisely determine the impact of these variations and discrepancies on the measurement properties of audit data and on the performance of audit programs. This study determined that such research is feasible with some, but not all, auditing programs.     

Is bird song a reliable signal of aggressive intent? A reply

We advocate assessing the reliability of signals of aggressive intent by eliciting aggressive signaling from a subject, giving the subject an opportunity to attack a model, and testing whether the subject’s displays predict a subsequent attack. Using this design, we found that most singing behaviors are poor predictors of attack in song sparrows (Melospiza melodia). Laidre and Vehrencamp (Behav Ecol Sociobiol, DOI 10.1007/s00265-007-0539-3, 2008) suggested altering our experimental design to make the model more realistic; it remains to be seen whether such design changes would change the association between display and attack. Laidre and Vehrencamp (Behav Ecol Sociobiol, DOI 10.1007/s00265-007-0539-3, 2008) also suggested that the reliability of soft song, the one display that predicts attack in song sparrows, can be explained by a vulnerability cost. We question the rationale for a vulnerability cost for this display and suggest instead that soft song has a competing functions cost, in that, by using soft song to counter an intruder, a male sacrifices other possible functions of vocal signaling.     

高层建筑火灾风险评估中一种具有置信度和方差的权系数

对评估中的权系数引入置信度和方差两个概念 ,为权系数提供更多的信息 ,便于决策者采用 ;针对作者在香港所作的高层建筑火灾风险因子评估系数 ,得到 16个风险因子的带置信度和方差的权系数 ,为火灾风险评估提供重要依据     

An integrated off-on line approach for increasing stability and effectiveness of automated controlled systems based on pump dependability—case study: Offshore industry

Automated controlled systems are vulnerable to faults. Faults can be amplified by the closed loop control systems and they can develop into malfunction of the loop. A control loop failure will easily cause production stop or malfunction at a petrochemical plant. A way to achieve a stable and effective automated system is to enhance equipment dependability. This paper presents a standard methodology for the analysis and improvement of pump performance to enhance total operational effectiveness and stability in offshore industry based on dependability. Furthermore, it is shown how a reliability–safety analysis can be conducted through equipment dependability indicators to facilitate the mitigation of hazard frequency in a plant. The main idea is to employ principle component analysis (PCA) and importance analysis (IA) to provide insight on the pumps performance. The pumps of offshore industries are considered according to OREDA classification. The approach identifies the critical pump and their fault through which the major hazards could initiate in the process. At first PCA is used for assessing the performance of the pumps and ranking them. IA is then performed for the worst pump which could have most impact on the overall system effectiveness to classify their components based on the component criticality measures (CCM). The analysis of the classified components can ferret out the leading causes and common-cause events to pave a way toward improving pump performance through design optimization and online fault detection which ultimately enhance overall operational effectiveness.     

Life extension reliability analysis of decommissioned transportable seamless steel gas cylinders: A case study

Life extension reliability analysis process of decommissioned transportable seamless steel gas cylinders is proposed based on reliability index and applied to a case study in this paper. The index was calculated in terms of material stress, material strength and their probabilistic distributions. Stresses were determined by membrane equations for cylindrical shell and finite element analysis for neck, shoulder and bottom. Yield strength was measured and chosen as material strength. Probabilistic distributions were determined by distribution of material hardness. Decommissioned gas cylinders, which corrode relatively more seriously than others, could be used in the analysis for conservatively determining life extension reliability. In addition, service life of gas cylinders could be extended on condition that their reliability was more than 0.99999. Finally, the proposed analysis process was applied to determine whether some decommissioned transportable seamless steel oxygen cylinders which were manufactured in 1970s could be life extended and shown to be effective.     

RANDAP: An integrated framework for reliability analysis of detailed action plans of combined automatic-operator emergency response taking into account control room operator errors

Automatic process control and control room operators supervision/intervention in an emergency are of critical importance in major hazard industries. These combined operator and automatic actions are defined in Detailed Action Plans (DAP). A framework has been proposed for analyzing the reliability, and hence the likelihood of success, of DAPs. The Reliability Block Diagram technique is utilized for modeling the reliability of integrated automatic-operator emergency actions. The focus is on incorporating operator's operational and cognitive errors in the process/equipment reliability analysis. For this purpose, the human reliability analysis method SPAR-H is utilized. The proposed framework was used for analyzing emergency response DAPs of a real process plant in order to check and improve its applicability. It is argued that the presented framework facilitates the DAP assessment process by performing Task Analysis, modeling the detailed tasks as well as reliability analysis, thereby uncovering the shortcomings of the designed DAPs. Besides, it provides a very effective, transparent tool with insight into improvement areas and directions for improving the reliability of DAPs.     

Sensor design for saltwater ingress detection in high reliable all-electric deep sea actuators

Subsea oil and gas production relies on Xmas Trees which are mounted on boreholes. Xmas Trees are an arrangement of different valve types and sizes actuated by hydraulic, electro-mechanic or all-electric actuators. All these actuators sharing problems with saltwater ingress and the re-sulting increased wear. This paper investigates potential effects which can be measured after saltwater ingress. Extensive testing is executed and the investigated effects are used for novel sensor designs. These designs are evaluated regarding certain requirements and a resulting sen-sor design is proposed for industrialization. The resulting sensor can then be used to collect new important data to support optimal maintenance in the subsea industry.