Fault tree analysis

Abstract: I The Nature Of Risk. Risk In Modern Society. Changing Attitudes Toward Risk. Is Increased Concern Justified?. Unique Risk Factors in Industrialized Society. Computers And Risk. The Role of Computers in Accidents. Software Myths. Why Software Engineering is hard. The Reality We Face. Causes Of Accidents. The Concept of Causality. Flaws in the Safety Culture. Ineffective Organizational Structure. Ineffective Technical Activities. Human Error And Risk. Do Humans Cause Most Accidents?. The Need for Humans in Automated Systems. Human Error as Human-Task Mismatch. Conclusions. The Role Of Humans In Automated Systems. Mental Models. The Human as Monitor. The Human as Backup. The Human as Partner. Conclusions. II Introduction To System Safety. Foundations Of System Safety. Safety Engineering Pre-World War II. Systems Theory. Systems Engineering. Systems Analysis. Fundamentals Of System Safety. Historical Development. Basic Concepts. Software System Safety. Cost and Effectiveness of System Safety. Other Approaches To Safety. Industrial Safety. Reliability Engineering. Application-Specific Approaches to Safety. III Definitions And Models. Terminology. Failure and Error. Accident and Incident. Hazard. Risk. Safety. Safety and Security. Accident And Human Error Models. Accident Models. Human Task and Error Models. Summary. IV Elements Of A Safeware Program. Managing Safety. The Role of General Management. Place in the Organizational Structure. Documentation. The System And Software Safety Process. The General Tasks. Conceptual Development. Design. Full-Scale Development. Production and Deployment. Operation. "Examples. Hazard Analysis. The Hazard Analysis Process. Types of System Models. General Types of Analysis. Limitations and Criticisms of Hazard Analysis. Hazard Analysis Models And Techniques. Checklists. Hazard Indices. Fault Tree Analysis. Management Oversight and Risk Tree (MORT) Analysis. Event Tree Analysis. Cause-Consequence analysis (CCA). Hazards and Operability Analysis (HAZOP). Interface Analyses. Failure Modes and Effects Analysis (FMEA). Failure Modes, Effects, and Criticality Analysis (FMECA). Fault Hazard Analysis (FHA). State Machine Hazard Analysis (SMHA). Task and Human Error Analysis Techniques. Evaluations of Hazard Analysis Techniques. Software Hazard And Requirements Analysis. Process Considerations. Requirements Specification Components. Completeness in Requirements Specifications. Completeness Criteria for Requirements Analysis. Constraint Analysis. Designing For Safety. The Design Process. Design Techniques. Design Modification and Maintenance. Design Of The Human-Machine Interface. General Process Considerations. Matching Tasks to Human Characteristics. Reducing Safety-Critical Human Errors. Providing Appropriate Information and Feedback. Training and Maintaining Skills. Guidelines for Safe HMI Design. Verification Of Safety. Dynamic Analysis. Static Analysis. Independent Verification and Validation. Summary.

Abstract: Introduction: Since 1975, a short course entitled "System Safety and Reliability Analysis" has been presented to over 200 NRC personnel and contractors. The course has been taught jointly by David F. Haasl, Institute of System Sciences, Professor Norman H. Roberts, University of Washington, and members of the Probabilistic Analysis Staff, NRC, as part of a risk assessment training program sponsored by the Probabilistic Analysis Staff. This handbook has been developed not only to serve as text for the System Safety and Reliability Course, but also to make available to others a set of otherwise undocumented material on fault tree construction and evaluation. The publication of this handbook is in accordance with the recommendations of the Risk Assessment Review Group Report (NUREG/CR-0400) in which it was stated that the fault/event tree methodology both can and should be used more widely by the NRC. It is hoped that this document will help to codify and systematize the fault tree approach to systems analysis.

Abstract: Bayesian Networks (BN) provide a robust probabilistic method of reasoning under uncertainty. They have been successfully applied in a variety of real-world tasks but they have received little attention in the area of dependability. The present paper is aimed at exploring the capabilities of the BN formalism in the analysis of dependable systems. To this end, the paper compares BN with one of the most popular techniques for dependability analysis of large, safety critical systems, namely Fault Trees (FT). The paper shows that any FT can be directly mapped into a BN and that basic inference techniques on the latter may be used to obtain classical parameters computed from the former (i.e. reliability of the Top Event or of any sub-system, criticality of components, etc). Moreover, by using BN, some additional power can be obtained, both at the modeling and at the analysis level. At the modeling level, several restrictive assumptions implicit in the FT methodology can be removed and various kinds of dependencies among components can be accommodated. At the analysis level, a general diagnostic analysis can be performed. The comparison of the two methodologies is carried out by means of a running example, taken from the literature, that consists of a redundant multiprocessor system.

Abstract: Introduction: Since 1975, a short course entitled "System Safety and Reliability Analysis" has been presented to over 200 NRC personnel and contractors. The course has been taught jointly by David F. Haasl, Institute of System Sciences, Professor Norman H. Roberts, University of Washington, and members of the Probabilistic Analysis Staff, NRC, as part of a risk assessment training program sponsored by the Probabilistic Analysis Staff. This handbook has been developed not only to serve as text for the System Safety and Reliability Course, but also to make available to others a set of otherwise undocumented material on fault tree construction and evaluation. The publication of this handbook is in accordance with the recommendations of the Risk Assessment Review Group Report (NUREG/CR-0400) in which it was stated that the fault/event tree methodology both can and should be used more widely by the NRC. It is hoped that this document will help to codify and systematize the fault tree approach to systems analysis.

Abstract: Reliability analysis of fault-tolerant computer systems for critical applications is complicated by several factors. Systems designed to achieve high levels of reliability frequently employ high levels of redundancy, dynamic redundancy management, and complex fault and error recovery techniques. This paper describes dynamic fault-tree modeling techniques for handling these difficulties. Three advanced fault-tolerant computer systems are described: a fault-tolerant parallel processor, a mission avionics system, and a fault-tolerant hypercube. Fault-tree models for their analysis are presented. HARP (Hybrid Automated Reliability Predictor) is a software package developed at Duke University and NASA Langley Research Center that can solve those fault-tree models. >