Activity-centric risk analysis for delay prediction in Indian tunnel projects

Arenal-type pyroclastic flows: A probabilistic event tree risk analysis

The risk assessment analysis is perceived as the most important stage in preparation of the major accident prevention documentation in accordance with the Directive 96/82/EC. The risk assessment alone is a complex process and several procedures and their modifications have been developed in practice, using various approaches to the task. ARAMIS (Accidental Risk Assessment Methodology for IndustrieS) methodology (Hourtlou, Salvi, 2003, ARAMIS, 2004) has been developed in order to unify the approach to risk assessment for major accidents and their impact on the environment.Project ARATech2013 – a tool for major accidents risk analysis, has been established with the aim to transform ARAMIS complex procedures into a software tool, which will simplify and make the risk assessment techniques more readily accessible. It is the coherence of the ARATech2013 tool and the number of prearranged and recommended steps that provide the wider user base with a useful alternative to the commonly used and often technically and methodologically challenging deterministic and probabilistic approaches used for risk assessment.ARATech2013 is a web-based modular tool, which enables to alternatively expand the functionality of the tool or gives its users the option to follow a simple pre-selected pathway without having to follow the entire major accidents risk assessment process. The tool is based on the following three core modules:risk source assessment module,representative scenarios determination module,accident impact assessment module.The risk source assessment module presents the initial stage of the risk analysis process. The users use the module to establish the basic information about the facility, i.e. a list of all types of equipment containing hazardous substances, physical - chemical properties of hazardous substances, their physical state and amount. The application automatically identifies the potentially hazardous equipment to undergo further detailed analysis and matches this equipment with appropriate potential critical events. The user is provided with an ability to add supplementary information for determination of potential domino effects.The representative scenarios determination module computes the frequency of various hazardous effects for the determined critical events. Each critical event is automatically assigned generic fault trees (Fault Tree Analysis - FTA) and event trees (Event Tree Analysis - ETA), which can be further modified by the user to match the real situation in the given establishment. The user has the option to use a generic frequency for each critical event or to determine the frequency using the in-built Fault Tree Analysis. The module offers a database of complex check lists of safety functions and barriers, which the user can assess and apply individually to each fault or event tree. This makes the tool highly valuable for assessing the effectiveness of risk management systems.The accident impact assessment module is an independent module for modelling of the hazardous event and the spatio-temporal distribution of hazardous effects. The model distinguishes among the different types of release of the substance from the equipment, the consequent cloud formation and its dispersion with the toxic, radiative or pressure effects. The module is interlinked with a web mapping portal for a quick projection of the impact of the hazardous event.

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.

Fault and event trees Fault and event trees are modeling tools used as part of a quantitative analysis of a system. Other semi-quantitative or qualitative tools such as failure modes and effects analysis (FMEA) are often performed in preparation for a more exact analysis. Such tools are outside the (quantitative) scope of this book, and the interested reader is referred to [Kumamoto and Henley, 1996], [Andrews and Moss, 1993]. These books also provide further information and more examples on fault tree modeling as does the Fault Tree Handbook [Vesely et al. , 1981]. Fault tree and event tree analyses are two of the basic tools in system analysis. Both methodologies give rise to a pictorial representation of a statement in Boolean logic. We shall concentrate on fault tree analysis, but briefly explain the difference in the situations modeled by event trees and fault trees. Event trees use ‘forward logic’. They begin with an initiating event (an abnormal incident) and ‘propagate’ this event through the system under study by considering all possible ways in which it can effect the behaviour of the (sub)system. The nodes of an event tree represent the possible functioning or malfunctioning of a (sub)system. If a sufficient set of such systems functions normally then the plant will return to normal operating conditions. A path through an event tree resulting in an accident is called an accident sequence .

Long lasting complicated processes and organizational features generate abundant risks in Engineering, Procurement and Construction (EPC) projects. Iran witnesses an unprecedented boom in engineering, procurement and construction activities at all levels with the government’s goal of diversifying its income away from oil dependence to commercial and industrial activities based on the fourth economical development plan. The number, size and complexity of new EPC projects have created an extra burden on the participants and resulted in lots of risks. It is important to identify and prioritize the important risks in Iran to help local and international companies to consider these important risks. Hence, risk identification and prioritization are influential factors in risk monitoring decisions (Ebrahimnejad et al., 2009). The risk management process aims to identify and assess project risks in order to enable them to be understood clearly and managed effectively. In fact, project risk management is a systematic way of looking at areas of risk and consciously determining how each area should be treated. It is a management tool that aims at identifying sources of risk and uncertainty, determining their impact, and developing appropriate management responses (Thomas, 2003.). There are many commonly used techniques for risk identification and prioritization separately. These techniques generate a list of risks that often does not directly assist the project manager in knowing where to focus risk management attention. Qualitative assessment can help to prioritize identified risks by estimating their probability and impact, exposing the most significant risks; this approach deals with risks one at a time and does not consider their possible correlations, and so also does not provide an overall understanding of the risk faced by the project as a whole (Hillson, 2002). Project risk prioritization is usually affected by numerous factors including the human error, data analysis and available information. The great uncertainty in projects often causes difficulty in assessing risk factors. However, many risk assessment techniques currently used in EPC projects are comparatively mature, such as fault tree analysis, event tree analysis, monte carlo analysis, scenario planning, sensitivity analysis, failure mode and effects analysis, program evaluation and review technique (Carr & Tah, 2001). In this paper, an applicable approach in an uncertain environment that can identify and prioritize project risks simultaneously is introduced. A decision approach is proposed that

Fuzzy logic for process safety analysis

Purpose This study aims to develop a comprehensive framework for addressing delays in tunnel construction projects by leveraging predictable risk factors. Tunnel projects often encounter scheduling delays due to inherent complexities and uncertainties, necessitating a proactive approach to prevent project underperformance. Design/methodology/approach The integrated risk prioritization and determination of activity-wise delay (IRPAD) framework is divided into four phases: identification and prioritization of risk factors, determination of activity-wise risk coefficients using MCDM-based methodology, obtaining the critical risk path, and developing an activity-wise risk matrix. Fault tree analysis (FTA) and event tree analysis (ETA) are employed to determine activity-wise risk coefficients based on expert responses. Findings The framework’s applicability in Indian tunnel projects is demonstrated through a real-world case study with 95% validation accuracy. The IRPAD framework enhances the delay analysis process and facilitates the provision of effective activity-wise mitigation measures. Practical implications The IRPAD framework predicts delays in infrastructure projects thus enhancing resilience and sustainability, supporting SDGs 9 and 11. It can be applied to a wide range of construction projects to improve project performance. Originality/value This research introduces novel concepts such as the three fold activity-wise risk matrix and the critical risk path, contributing to the development of the IRPAD framework for delay reduction. This framework offers valuable insights to practitioners in the construction industry.

The operational safety assessment is an important part of a safety case for the deep geological repository of spent fuels. It consists of different stages such as the identification of initiating events, event tree analysis, fault tree analysis, and evaluation of exposure doses to the public and radiation workers. This study develops a probabilistic safety assessment method for the operational safety assessment and establishes an assessment framework. For the event and fault tree analyses, we propose the advanced information management system for probabilistic safety assessment (AIMS-PSA Manager). In addition, we propose the Radiological Safety Analysis Computer (RSAC) program to evaluate exposure doses to the public and radiation workers. Furthermore, we check the applicability of the assessment framework with respect to drop accidents of a spent fuel assembly arising out of crane failure, at the surface facility of the KRS+ (KAERI Reference disposal System for SNFs). The methods and tools established through this study can be used for the development of a safety case for the KRS+ system as well as for the design modification and the operational safety assessment of the KRS+ system.

The aim of this paper is to develop a methodology for risk analysis, assessment and management using the event tree method. A sample sequence of risk analysis actions is shown with the use the event tree method in determining the probability of realizing a dangerous event including an exemplary event tree pattern according the example under consideration and with the possibility of calculations and for determining the risk at the accepted value of the damage. A methodology for risk analysis is proposed based on the event tree applicable to student training on risk analysis and management.

A safety analysis was performed to determine possible causes of coal falling in the bulk coal discharge process using a methodology for risk analysis based on a combination of Fault tree analysis (FTA), event tree analysis (ETA) and BowTie (BT). The steps for risk assessment were the following: Description bulk coal discharge process, Event sequence modeling where logic models (ETA; FTA; BT) and Consequence assessment. The bulk coal discharge process is performed using cranes which are deployed in the terminal, in parallel to the coal holds of the ship. The hydraulic grabs descend onto the ship holds at an angle, determined by considerations of wind direction and intensity, which shovel up the coal and lift it upwards. The grabs move along the crane handle, and open up above the funnel which pours the coal into the coal conveyor, this procedure is repeated sequentially until empty the ship. Results from BT allow to identify three possible causes of coal falling. Two of which are attributed to technical factors such as crane failure and grab failure, while the other cause is related to human factors such as lack operational discipline (OD). Three barriers were identified to prevent the fall of coal: certified crane, hermetic grabs and operational discipline. Two mitigating barriers were identified: Vacuum truck to clean the coal in the pier and tablecloth to avoid coal fall in the sea. Finally, the consequences if not working barriers are: coal built up on pier and sea pollution. However, it can't be ensured that the stranding of coal on the beaches is directly caused by port operations.KeywordsFault Tree Analysis (FTA)Event Tree analysis (ETA)Bow tie (BT)Bulk coal discharge

Today there is used an overwhelming number of different risk analyses techniques with acronyms such as: FMEA (Failure Modes and Effects Analysis) and its extension FMECA (Failure Mode, Effects, and Criticality Analysis), DRBFM (Design Review by Failure Mode), FTA (Fault Tree Analysis) and and its extension ETA (Event Tree Analysis), HAZOP (Hazard & Operability Studies), HACCP (Hazard Analysis and Critical Control Points) and What-if/Checklist. However, the most used analysis techniques in the mechanical and electrical industry are FMEA and FTA. In FMEA, which is an inductive method, information about the consequences and effects of the failures is usually collected through interviews with experienced people, and with different knowledge i.e., cross-functional groups. The FMEA is used to capture potential failures/risks & impacts and prioritize them on a numeric scale called Risk Priority Number (RPN) which ranges from 1 to 1000. FTA is a deductive method i.e., a general system state is decomposed into chains of more basic events of components. The logical interrelationship of how such basic events depend on and affect each other is often described analytically in a reliability structure which can be visualized as a tree. Both methods are very time-consuming to be applied thoroughly, and this is why it is oftenly not done so. As a consequence possible failure modes may not be identified. To address these shortcomings, it is proposed to use a combination of FTA and FMEA.

Probabilistic safety assessment (PSA) which plays a crucial role in risk evaluation is a quantitative approach intended to demonstrate how a nuclear reactor meets the safety margins as part of the licensing process. Despite PSA merits, some shortcomings associated with the final results exist. Conventional PSA uses crisp values to represent the failure probabilities of basic events. This causes a high level of uncertainty due to the inherent imprecision and vagueness of failure input data. In this paper, to tackle this imperfection, a fuzzy approach is employed with fault tree analysis and event tree analysis. Thus, instead of using the crisp values, a set of fuzzy numbers is applied as failure probabilities of basic events. Hence, in the fault tree and event tree analysis, the top events and the end-states frequencies are treated as fuzzy numbers. By introducing some fuzzy importance measures the critical components which contribute maximum to the system failure and total uncertainty are identified. As a practical example, under redesign Iranian heavy water research reactor loss of coolant accident is studied. The results show that the reactor protection system has the largest index in sequences lead to a core meltdown. In addition, the emergency core cooling system has a main role in preventing abnormal conditions.

The Division of Applications and Software is a part of the Academic Support Unit (UPA) for Information and Communication Technology at Universitas Jember (UNEJ) or UPA TIK UNEJ. Based on interviews, UPA TIK UNEJ has not yet implemented risk management, leading to recurring issues in their IT services. Risk management is crucial for preventing and mitigating negative impacts that can harm the organization. Additionally, it is a requirement for internal quality management system audits, according to UNEJ Rector's Decision Number 20588/UN25/LL/2018. This study aims to identify, analyze, and assess potential risks in the Division of Applications and Software at UPA TIK UNEJ and to apply Bow Tie Analysis (BTA) to identify preventive and mitigative actions for the highest-rated risks. The approach used is ISO 31000:2018, which provides a comprehensive framework for risk management. For in-depth risk analysis, the BTA method, combining event tree analysis (ETA) and fault tree analysis (FTA), is utilized. The research begins with context establishment through interviews, followed by risk identification, analysis, assessment, and mitigation. The results show 21 risks identified in the process of developing information systems or applications. The top three priority risks are coded R02, R04, and R19. The second priority includes 17 risks, and the third priority includes 1 risk.

Nowadays in offshore industry there are emerging hazards with vague property such as act of terrorism, act of war, unforeseen natural disasters such as tsunami, etc. Therefore industry professionals such as offshore energy insurers, safety engineers and risk managers in order to determine the failure rates and frequencies for the potential hazards where there is no data available, they need to use an appropriate method to overcome this difficulty. Furthermore in conventional risk based analysis models such as when using a fault tree analysis, hazards with vague properties are normally waived and ignored. In other word in previous situations only a traditional probability based fault tree analysis could be implemented. To overcome this shortcoming fuzzy set theory is applied to fault tree analysis to combine the known and unknown data in which the pre-combined result will be determined under a fuzzy environment. This has been fulfilled by integration of a generic bow-tie based risk analysis model into the risk assessment phase of the Risk Management (RM) cycles as a backbone of the phase. For this reason Fault Tree Analysis (FTA) and Event Tree Analysis (ETA) are used to analyse one of the significant risk factors associated in offshore terminals. This process will eventually help the insurers and risk managers in marine and offshore industries to investigate the potential hazards more in detail if there is vagueness. For this purpose a case study of offshore terminal while coinciding with the nature of the Caspian Sea was decided to be examined.

Currently qualitative as well as quantitative safety analysis of railway systems are usually conducted through Fault Tree Analysis (FTA) and Event Tree Analysis (ETA). FTA and ETA display the causalities and consequences of hazards or accidents by means of linear event sequences, which makes it difficult to incorporate non-linear relationships such as feedback. The repair of failure system components is not considered in traditional FTA and ETA. Moreover, quantitative safety evaluation by FTA and ETA requires that failure events should be statistically independent. Considering these issues, we propose an approach of conducting qualitative as well as quantitative safety evaluation of the CTCS-3 with stochastic Coloured Petri Nets (CPNs). The hierarchical CPN model of the CTCS-3 takes the scenarios, movement of trains, the failure and repair of system components into account. The occurrence times of hazardous events of a CTCS-3 system is quantitatively evaluated with the numerical data collected during the simulation of the system model. The evaluation results demonstrate the feasibility of the proposed approach.