Application Of Safety Analysis Research Articles

An evaluation of time-to-collision as a surrogate safety measure and a proposal of a new method for its application in safety analysis

ABSTRACT Various surrogate safety measures have been introduced, of which Time-to-Collision (TTC) is the most well-known and commonly applied indicator. TTC first was defined as the time remaining prior to a collision if the path and speed of vehicles are maintained as a constant. Various modifications have been applied to this indicator to increase the efficiency of TTC. However, there is still no specific platform that shows how all of these modifications can be applied simultaneously. Thus, this paper first reviews the modifications that have been made to TTC; subsequently, a comprehensive framework is proposed for the application of this indicator for different types of conflicts, while considering all previous modifications. The framework is then applied for microscopic traffic data collected in Tehran. Results indicate that there is a great difference between the results of different versions of TTC for collision probability prediction. However, the proposed procedure might be beneficial in increasing the precision and accuracy of detecting dangerous encounters.

Data-Driven Formal Reasoning and Their Applications in Safety Analysis of Vehicle Autonomy Features

Analyzing the safety of automotive systems at the application level is -especially challenging as often very complex or even incomplete models are available. The authors combine formal reasoning with simulation data to effectively -validate safety or estimate worst case situations of automotive control systems. —Hans-Joachim Wunderlich, Universitat Stuttgart

소프트웨어 개발 프로세스에서의 안전성 분석 및 관리 활동의 적용방안

소프트웨어 개발 프로세스에서의 안전성 분석 및 관리 활동의 적용방안

Fracture Toughness of Ferritic Steels: Lower Bounds and their Implications on Testing and Application

For physical reasons fracture toughness KJc of ferritic steels in the brittle-to-ductile transition regime is affected by a pronounced scatter, which requires statistical methods to be applied for evaluation of test results as well as for application in safety analysis of structures. For this purposes the probabilistic Master-Curve-approach according to ASTM E1921 is often used. However, for engineering purposes like a screening safety analysis of a defect-containing component it is usually preferable to use a deterministic lower bound. However, within the framework of ASTM-standards there is no possibility to determine KIc experimentally. So KIc needs to be determined indirectly from the reference temperature T0. In the present paper it is shown how lower bounds of fracture toughness – either plane strain KIc for large components or thickness-dependent KJc for smaller ones - can be derived from T0, and how the latter can be determine with sufficient accuracy from one or a few KJc values.

CFD-based atmospheric dispersion modeling in real urban environments

AbstractThe process of CFD model application for atmospheric dispersion modeling is presented. Increasing the CPU power opens new possibilities of the CFD approach application for consequence analysis in real complex urban environments. As successful CFD simulation is directly dependent on the quality and complexity of the computational mesh, a new methodology of transferring the Geographic Information System (GIS) data to the computational mesh can be utilized. A user software for importing and manipulation with the GIS data and their subsequent transfer to an instructional file for the generation of the computational mesh was prepared and tested. The introduced methodology is relatively simple and it requires only a small amount of input data. The process of creating a computational mesh is very straightforward and fast, which enables the application of CFD modeling in urban environments in all fields of engineering applications in safety analysis. Several recommendations concerning proper definition of boundary conditions for atmospheric dispersion modeling were summarized. The presented approach was tested on a realistic case study of liquefied chlorine release in a real town. Results obtained by the CFD approach were compared with those obtained by a simpler but standard integral model.

Safety analysis in process facilities: Comparison of fault tree and Bayesian network approaches

Safety analysis in gas process facilities is necessary to prevent unwanted events that may cause catastrophic accidents. Accident scenario analysis with probability updating is the key to dynamic safety analysis. Although conventional failure assessment techniques such as fault tree (FT) have been used effectively for this purpose, they suffer severe limitations of static structure and uncertainty handling, which are of great significance in process safety analysis. Bayesian network (BN) is an alternative technique with ample potential for application in safety analysis. BNs have a strong similarity to FTs in many respects; however, the distinct advantages making them more suitable than FTs are their ability in explicitly representing the dependencies of events, updating probabilities, and coping with uncertainties. The objective of this paper is to demonstrate the application of BNs in safety analysis of process systems. The first part of the paper shows those modeling aspects that are common between FT and BN, giving preference to BN due to its ability to update probabilities. The second part is devoted to various modeling features of BN, helping to incorporate multi-state variables, dependent failures, functional uncertainty, and expert opinion which are frequently encountered in safety analysis, but cannot be considered by FT. The paper concludes that BN is a superior technique in safety analysis because of its flexible structure, allowing it to fit a wide variety of accident scenarios.

Integration of safety analysis in model-driven software development

Safety critical software requires integrating verification techniques in software development methods. Software architectures must guarantee that developed systems will meet safety requirements and safety analyses are frequently used in the assessment. Safety engineers and software architects must reach a common understanding on an optimal architecture from both perspectives. Currently both groups of engineers apply different modelling techniques and languages: safety analysis models and software modelling languages. The solutions proposed seek to integrate both domains coupling the languages of each domain. It constitutes a sound example of the use of language engineering to improve efficiency in a software-related domain. A model-driven development approach and the use of a platform-independent language are used to bridge the gap between safety analyses (failure mode effects and criticality analysis and fault tree analysis) and software development languages (e.g. unified modelling language). Language abstract syntaxes (metamodels), profiles, language mappings (model transformations) and language refinements, support the direct application of safety analysis to software architectures for the verification of safety requirements. Model consistency and the possibility of automation are found among the benefits.

Comprehensive uncertainty and sensitivity analysis for coupled code calculations of VVER plant transients

The development of coupled codes, combining thermal-hydraulic system codes and 3D neutron kinetics codes, is an important step to perform best-estimate calculations for plant transients of nuclear power plants. For applications in safety analysis, these coupled codes should be validated by benchmark calculations and, preferably, by comparison with plant transient data from operating plants. In addition, the results should be supplemented by applying uncertainty and sensitivity analysis methods, which allow to identify relevant parameters of models and solution procedures affecting the results and to quantify their relative importance. Both objectives were part of the VALCO project. The aspect of validation is presented in [S. Mittag, et al., 2004. Neutron-Kinetic Code Validation against Measurements in the Moscow V-1000 Zero-Power Facility, in press; T. Vanttola et al., 2004. Validation of coupled codes using VVER plant measurements, in press], the aspect of a comprehensive uncertainty and sensitivity analysis for coupled code calculations is the topic of this contribution. The results and experiences obtained by the analysis for two plant transients in a VVER-440 and a VVER-1000, respectively, are presented and discussed.

Risk and failure aspects in twin screw extrusion

There is a multitude of norms and general guidelines relevant to machine safety. Two possibilities are discussed which allow a systematic analysis of hazards concerning processes, process steps and machines down to their components, and which allow appropriate measures to be defined. It concerns the so-called FMEA (Fehler-Mo¨glichkeits- und Einfluss-Analyse = Fault Occurrence and Influence Analysis) and classical safety analysis. Using some examples from the field of extrusion technology, the application of safety analysis is demonstrated and the measures are described that have to be realized to guarantee protection for people.

QUASA: A method for assessing the quality of safety analysis

Rouhiainen, V., 1992. QUASA: A method for assessing the quality of safety analysis. Safety Science, 15:155–172 The increasing application of safety and risk analysis makes it necessary to have methods and criteria for evaluating the contents and results of such analyses. The main problems encountered in the applicability of safety analysis are the quality of the analyses and the resources needed for the analyses. Quality systems developed for other industrial purposes offer means for developing systems which support the quality management of safety analysis. These issues constitute the subject matter of this investigation. This paper describes a new method for assessing the quality of safety analyses. The method is based on evaluation of the analysis process and identification of its deficiencies by means of a checklist. For validating the method, the interassessor reliability has been examined by conducting parallel independent assessments of the same safety analysis. The validity of the method in uncovering deficiencies in the safety analysis was examined by using information on critical incidents collected from the analysed activity and descriptions of accidents as the reference. The importance of the observed deficiencies was evaluated by taking the effect of the incidents on safety as the criteria. The results of the study demonstrated that this new method is capable of revealing most of the significant deficiencies in a safety analysis.