Risk Assessment in Bridge Construction Projects Using Fault Tree and Event Tree Analysis Methods Based on Fuzzy Logic

2015 ◽  
Vol 1 (3) ◽  
Author(s):  
Gholamreza Abdollahzadeh ◽  
Sima Rastgoo
Keyword(s):  
Fuzzy Logic ◽  
Traditional Approach ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Mitigation Strategies ◽  
Fuzzy Arithmetic ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Risk Event

In this paper, interruption risk in construction activities of bridge projects is assessed in order to identify the main causes of its occurrence and also to determine the potential outcomes resulted from the risk occurrence. To do this, fault tree and event tree analysis (ETA) methods are applied. As the application of the traditional approach of these two methods is difficult in many cases due to limited access to information, fuzzy arithmetic can be considered as a useful tool. In this research, first, fault tree structure is created according to consequences resulted from the Delphi method. Then, the probability of risk occurrence is calculated by applying fault tree analysis (FTA) based on fuzzy logic. By establishing the structure of fault tree related to the failure risk of mitigation strategies, the main causes relating to failure of strategies are identified. The structure of the event tree is created using the obtained results; moreover, the expected monetary value (EMV) of risk event is computed. Finally, to validate the results obtained, a model is created by Monte Carlo simulation and then the results obtained by applying the two methods are compared. The EMV of the risk event evaluated in this paper is determined to be 9.93% of the project baseline cost.

scholarly journals Methodology for tunnel risk assessment using fault and event tree analysis

2021 ◽  
Author(s):  
Zlatko Zafirovski ◽  
Vasko Gacevski ◽  
Zoran Krakutovski ◽  
Slobodan Ognjenovic ◽  
Ivona Nedevska
Keyword(s):  
Risk Assessment ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Economic Consequences ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Geological Conditions ◽  
Hazard And Risk ◽  
Complex Solutions

The intense demand and construction of tunnels is accompanied by uncertainties. The reason for appearance of uncertainties are the complex solutions and conditions for these structures. Location and dimensions are becoming more challenging, and the construction is predicted in complexed geological conditions, leading to application of new approaches, methodologies and technologies by the engineers. Most of the uncertainties and unwanted events in tunnelling occur in the construction phase, which generally leads to economic consequences and time losses. For easier handling of the uncertainties, they should be anticipated and studied within a separate part of each project. One of the newer approaches to dealing with uncertainties is hazard and risk assessment and defining ways to deal with them i.e. management. Hazards and risks can be analysed qualitatively and quantitatively. The quantitative analysis, examines the causes and consequences in more detail way and gives explanation of the dependencies. With the quantitative approach, a more valuable information for decision-making can be provided. There are various models and methods used for the quantification of hazards and risks. This paper presents a methodology in which the fault tree analysis and event tree analysis are used in combination to obtain quantitative results. The fault tree analysis is used for assessment of various hazards and the different ways and reasons that cause them. The event tree analysis is a method for assessing the possible scenarios, which follow after a certain hazard i.e. the consequences that may occur in the project. These trees represent graphic models combined with a mathematical (probabilistic) model, which give the probability of occurrence of the risks.

Semi-Supervised Machine Learning Algorithms for Classifying the Imbalanced Protocol Flows

2014 ◽  
Vol 536-537 ◽  
pp. 809-814
Author(s):  
Lin Lin Li ◽  
Xiao Yi Zhang ◽  
Xia Zhang ◽  
Qing Li
Keyword(s):  
Fault Tree Analysis ◽  
Machine Learning Algorithms ◽  
Supervised Machine Learning ◽  
Event Tree ◽  
Level Crossing ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Minimal Cut Set ◽  
Risk Event ◽  
Precautionary Measures

The collision that between a car and a train is the main type of accidents in the case railway level-crossing, which is proved by the arrangement diagram analysing. The fault tree analysis and the event tree analysis are used to assess the level of the risk of the level-crossing quantificationally. Some conclusions can be drawn: the collision of the railway level-crossing that between a car and a train will happen 2.552 in a year, which can bring 0.061 equivalent fatalities. This paper puts forward some precautionary measures that based on the minimal cut set of the collision of the accident and the most probable or the highest risk event.

scholarly journals Risk Assessment of Petroleum Products Loading Arm by BTA Technique

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Mostafa Mirzaei Aliabadi ◽  
Iraj Mohammadfam ◽  
Samane Khorshidikia
Keyword(s):  
Risk Assessment ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Petroleum Products ◽  
Event Tree ◽  
Tree Analysis ◽  
Probability Of Occurrence ◽  
Risk Event ◽  
Bow Tie

Background: Loading of petroleum products consists of several parts, of which the arm platform section is known to be the source of most accidents. Objectives: Therefore, this study was done to evaluate the risk of arm loading platforms using the bow-tie analysis (BTA) technique to identify the causes and the probability of occurrence of hazardous events. Methods: In this study, we first identified the risks of the loading arm using the expert’s judgment. The risk of overflow is considered as the top event. Then, the basic events were identified by the fault tree analysis (FTA), and the possible consequences of the top event were predicted using the event tree. Next, using the computational equations, the probability of spillover and its consequences were calculated. The path of the risk event from the causal phase to the consequent phase was also illustrated by sketching the structure of the BTA. Results: A total of 14 basic events and 8 intermediate events were involved in the occurrence of the top event, and 5 consequences were identified for the risk of spillover. The probability of the top event occurring was calculated to be 3.12 × 10-7. Conclusions: According to the results of this study, tank overflow is one of the most important hazards in the loading arm section.

scholarly journals RISK MANAGEMENT ON THE WARSHIP TASK OPERATIONS

JOURNAL ASRO ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 23
Author(s):  
Diksono Diksono ◽  
I Made Jiwa ◽  
Suparno Suparno
Keyword(s):  
Risk Mitigation ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Main Tool ◽  
Main Task ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Formal Safety Assessment ◽  
The Impact

ABSTRACT The main task of the Indonesia Navy is to enforce the law and maintain security in the territorial sea of national jurisdiction, so that the Indonesian Navy is required to have the main tool of weapons systems (Alutsista) are always ready to carry out the task. The frequent occurrence of accidents experienced by the Indonesian Warship (KRI). This reduces the ability of Warship in performing the task. The purpose of this research is to investigate the causes and effects of accidents, and seek risk mitigation that is considered appropriate. Formal Safety Assessment (FSA) is a structured and systematic methodology used for maritime safety analysis. The fault tree analysis is used to investigate the cause of marine accidents and the event tree analysis is used to determine the impact of an accident. The results of this study are FSA can be effectively applied in accident investigations, although the calculation of cost benefit analysis for warships can be ignored because the Warship task cannot be compared to the value of money.  Keywords: Task Operation, Warship, FSA, fault tree analysis, event tree analysis

scholarly journals Evaluation of the Level of Reliability in Hazardous Technological Processes

2020 ◽  
Vol 11 (1) ◽  
pp. 134
Author(s):  
Darja Gabriska
Keyword(s):  
Reliability Analysis ◽  
Failure Rate ◽  
System Reliability ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Entire System ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Technical Standards ◽  
Tree Analysis

In an automated systems environment is very important to predicted failures or unexpected situations to achieve system reliability. Failure of such systems can cause serious property damage, the environment, damage to human health or cause death. The essential task is to determine the tolerable and acceptable risk. The required level of risk for safety-critical systems can be achieved by using international technical standards and applying safety functions. Safety functions are implemented using an electrical/electronic/programmable electronics (E/E/PE) safety-related system. Technical standards offer the aspect of balancing risk tolerability according to the relevant, reliable safety functions. Based on the specific architecture of the whole system, it is possible to determine the maximum failure rate of the probability of failure on demand (PFDSYS) of the selected architecture. Subsequent application of reliability analysis using the event tree analysis (ETA) and fault tree analysis (FTA) methods can optimize the failure rate of the entire system. Application of reliability analysis using event tree analysis (ETA) and fault tree analysis (FTA) methods can only theoretically optimize the failure rate of the entire system with constant initial conditions and constant parameters of the reliability functions. The article proposes a new methodology for dynamic analysis of the state of system reliability as a function of the system operation time, maintenance frequency and system architecture. As a result of the methodology is a library of standard element architectures and simulation models which allows predicting and optimizing the reliability of E/E/PE safety-related systems.

scholarly journals Ανάπτυξη και εφαρμογή μεθοδολογίας εκτίμησης διακινδύνευσης σε ναυπηγεία

2015 ◽  
Author(s):  
Νικόλαος Φραγκιαδάκης
Keyword(s):  
Fuzzy Inference System ◽  
Fuzzy Inference ◽  
Fault Tree Analysis ◽  
Quantitative Risk Assessment ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Inference System ◽  
Tree Analysis ◽  
Neuro Fuzzy ◽  
Bow Tie

Στόχος αυτής της διατριβής είναι η δημιουργία μοντέλου που θα οδηγεί σε μια Ποσοτική Εκτίμηση Επαγγελματικής Διακινδύνευσης (Quantitative Risk Assessment, QRA) εργαζομένων στην ναυπηγική και ναυπηγοεπισκευαστική βιομηχανία με γνώμονα το εργατικό ατύχημα, επιχειρώντας να συμβάλλει στην αντιμετώπιση ενός προβλήματος που έχει σημαντικές κοινωνικές αλλά και οικονομικές διαστάσεις. Ακολουθήθηκαν δύο ανεξάρτητοι οδοί που συμπληρώνουν η μία την άλλη.Η πρώτη οδός οδήγησε στην ανάπτυξη ενός Αναλυτικού Μοντέλου, ικανό να περιγράφει τους μηχανισμούς σύνδεσης μεταξύ αιτίου- αιτιατού - συνεπειών εργατικών ατυχημάτων σε ναυπηγικές εργασίες και να οδηγεί υπό προϋποθέσεις σε μια ολοκληρωμένη QRA. Το μοντέλο στηρίχθηκε στον εντοπισμό και στην αξιολόγηση των πηγών κινδύνου, καθώς και άλλων επιβαρυντικών παραγόντων μέσα στο εργασιακό περιβάλλον ενός ναυπηγείου. Τεχνικές χρήσης επαγωγικών μοντέλων όπως τα δέντρα γεγονότων (Event Tree Analysis, ETA) και τα δέντρα σφαλμάτων (Fault Tree Analysis, FTA) χρησιμοποιήθηκαν. Τα επαγωγικά μοντέλα συνδέθηκαν τελικά σε μια ολοκληρωμένη δομή “BOW TIE”, στην οποία απεικονίζεται σαφώς η σχέση των γενεσιουργών αιτιών και των επιβαρυντικών παραγόντων που δύναται να οδηγήσουν στη δημιουργία ενός συμβάντος, καθώς και η πορεία από το συμβάν στις πιθανές συνέπειες μέσω των αμβλυντικών παραγόντων που συνθέτουν τα ανεξάρτητα επίπεδα προστασίας (Independent Layers of Protection, ILPs). Έτσι παρίστανται οι παράγοντες που συγκροτούν τη διακινδύνευση, δηλαδή η πιθανότητα ενός συμβάντος αφενός και οι πιθανές συνέπειες αφετέρου. Για την καλύτερη κατανόηση και τεκμηρίωση του μοντέλου διενεργήθηκαν τεχνικές ανάλυσης και αναγνώρισης κινδύνου για συγκεκριμένες χαρακτηριστικές περιπτώσεις (HAZID), κατασκευάστηκαν διαγράμματα ροής για αυτές τις περιπτώσεις και αριθμητικό παράδειγμα υπολογισμού της διακινδύνευσης για μια εκ των περιπτώσεων.Η δεύτερη οδός οδήγησε στην δόμηση ενός έμπειρου συστήματος, στηριζόμενου σε κανόνες ασαφούς λογικής και ασαφούς συμπερασμού, που χρησιμοποιεί την παρεχόμενη πληροφορία από δεδομένα εργατικών ατυχημάτων στη ναυπηγική βιομηχανία, τα οποία έχουν συγκεντρωθεί από ναυπηγοεπισκευαστικές μονάδες, μέσω της χρήσης στατιστικής ανάλυσης και με τη χρήση υπολογιστικών τεχνικών soft computing. Επιλέχθηκε η δημιουργία ενός «Ασαφούς Συστήματος Συμπερασμού» (Fuzzy Inference System, FIS) που στηρίζεται στα προσαρμοζόμενα νευρωνικά δίκτυα (Adaptive Neural Networks, AN). Τα καταγεγραμμένα δεδομένα στοιχεία υπέστησαν στατιστική επεξεργασία και καθορίστηκαν οι παράμετροι και τα δεδομένα για την τροφοδότηση, την εκπαίδευση και τον έλεγχο των αποτελεσμάτων του Προσαρμοζόμενου Νευρωνικού Ασαφούς Συστήματος Συμπερασμού (Adaptive Neuro-Fuzzy Inference System ANFIS).Το μοντέλο “BOW TIE” αποδείχθηκε ικανό να οδηγήσει σε ποιοτικά συμπεράσματα όπως ο εντοπισμός των πηγών κινδύνου, των επιβαρυντικών αλλά και των αμβλυντικών παραγόντων αλλά και να τεκμηριώσει ποσοτικά κάθε μέτρο βελτίωσης της ασφάλειας με στόχο τη μείωση της διακινδύνευσης.Το μοντέλο ANFIS αποδεδείχθηκε μια εφικτή μέθοδος προσομοίωσης της πολύπλοκης σχέσης μεταξύ των παραμέτρων που εμπλέκονται σε ένα εργατικό ατύχημα στη ναυπηγική βιομηχανία, εκμεταλλευόμενο ήδη υπάρχοντα και κατάλληλα στατιστικά επεξεργασμένα ιστορικά στοιχεία εργατικών ατυχημάτων, αποτελώντας ένα εργαλείο ικανό να κάνει προβλέψεις και να οδηγεί σε ασφαλή συμπεράσματα, σε μικρό υπολογιστικό χρόνο.

A Novel Weakest t-Norm based Fuzzy Importance Measure for Fuzzy Fault Tree Analysis of Combustion Engineering Reactor Protection System

2019 ◽  
Vol 27 (06) ◽  
pp. 949-967 ◽  
Author(s):  
Mohit Kumar
Keyword(s):  
Fault Tree ◽  
Fault Tree Analysis ◽  
Protection System ◽  
Importance Measure ◽  
Fuzzy Arithmetic ◽  
Tree Analysis ◽  
Uncertainty Range ◽  
Expert Opinions ◽  
Fuzzy Fault Tree Analysis ◽  
Reactor Protection System

Recently, a new fuzzy fault tree analysis (FFTA) has been developed to propagate and quantify the epistemic uncertainties occurring in qualitative data such as expert opinions or judgments. It is well known that the weakest triangular norm (Tw) based fuzzy arithmetic operations preserve the shape of the fuzzy numbers, provide more exact fuzzy results and effectively reduce uncertainty range. The objective of this paper is to develop a novel Tw-based fuzzy importance measure to identify the critical basic events in FFTA. The proposed approach has been demonstrated by applying it to a case study to identify the critical components of the Group 1 of the U.S. Combustion Engineering Reactor Protection System (CERPS). The obtained results are then compared to the results computed by the existing well-known importance measures of conventional as well as FFTA. The computed results confirm that the proposed Tw -based importance measure is feasible to identify the critical basic events in FFTA in more exact way.

scholarly journals Quantitative Risk Assessment of Biogas Plant – Determination of Assumptions and Estimation of Selected Top Event

2019 ◽  
Author(s):  
Petr Trávníček ◽  
Luboš Kotek ◽  
Tomáš Koutný ◽  
Tomáš Vítěz
Keyword(s):  
Risk Assessment ◽  
Chemical Industry ◽  
Fault Tree Analysis ◽  
Quantitative Risk Assessment ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Hazardous Chemical ◽  
Biogas Plants

Biogas plants are a specific facility from the QRA (Quantitative Risk Assessment) methodologies' point of view, especially in the case of the determination of the event frequency of accident scenarios for biogas leakage from a gas holder and subsequent initiation. QRA methodologies determine event frequencies for different types of accident events related to vessels made of steel. Gas holders installed at biogas plants are predominantly made of other materials and are often integrated with the fermenter. It is therefore a specific type of gas holder, differing from that which is commonly used in the chemical industry. In addition, long-term experience is not available for the operation of biogas plants, unlike in the chemical industry. The event frequencies listed in the QRA methodologies are not relevant for the risk assessment of biogas plants. This work is focused on setting the prerequisites for QRA of biogas storage, including for example: information on hazardous chemical substances occurring at biogas plants, their classification, and information on the construction of integrated gas holders. For the purpose of the work, a scenario was applied where the greatest damage (to life or property) is expected. This scenario is the leakage of the total volume of hazardous gas substance from the gas holder and subsequent initiation. Based on this information, a "tree" was processed for "Fault Tree Analysis" (FTA), and frequencies were estimated for each event. Thereafter, an "Event Tree Analysis" was carried out. This work follows up on a discussion by experts on the determination of scenario frequencies for biogas plants that was conducted in the past.

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