Operational Safety Assessment Research Articles

Post-earthquake train operation safety assessment model based on machine learning

Abstract Assessing the seismic risk to high-speed rail systems with limited structural damage data is a challenging task. This study employs machine learning algorithms to predict the wheel-rail forces of high-speed trains operating under post-earthquake conditions, particularly when infrastructure along the railway is damaged. By developing a post-earthquake train operation safety assessment model, this paper effectively predicts the impact of track irregularities induced by different earthquake intensities on wheel-rail interactions. The results obtained through feature selection and regression analysis using the Random Forest algorithm provide valuable insights into key safety indicators for post-earthquake train operations. Compared to traditional multibody dynamic models, this approach significantly improves the efficiency of analysis and computation. An analysis of the results across multiple speed levels reveals that trains operating at 250 km/h face derailment risks when subjected to high-intensity earthquakes (PGA > 0.6 g). The proposed predictive safety assessment model demonstrates that adjusting train speeds according to seismic intensity can effectively enhance operational safety, offering critical support for post-earthquake emergency recovery efforts.

Evaluation of Operational Safety Risk in Wastewater Treatment Plants Based on WSR and Matter–Element Extension Theory

Wastewater treatment plants are of significant importance in facilitating China’s urbanization process. The fundamental purpose of wastewater treatment plants is to control water pollution and protect the environment. It is therefore essential that they are operated in a safe manner in order to achieve this goal. In order to guarantee a systematic and objective assessment of the operational safety risks inherent to wastewater treatment plants, the Wuli–Shili–Renli (WSR) theory has been introduced. Accordingly, a three-dimensional evaluation index system was developed for the assessment of these risks. A combination of subjective and objective methods utilizing game theory was employed to determine comprehensive risk factor weights. Subsequently, the material–element extension theory model was implemented in a wastewater treatment plant situated in the northern region of the Changchun Development Zone. The assessment classified the plant as Level 1 (safe), although it was determined that improvements in accident prevention are necessary. This study presents a robust framework for operational safety assessment that contributes to enhanced risk management and the long-term reliability of wastewater treatment operations. The results of the sensitivity analyses provide substantial evidence of the reliability and validity of the model.

Assessment of Power Equipment Operational Safety in the Sustainable Management of Residual Lifespan

Introduction. Ensuring the safe operation of energy facilities is a critical issue at all life cycle stages. It is associated with the adoption of management decisions when rescheduling and assessing the remaining resources, which are made based on a comprehensive assessment of the technical condition of the equipment, taking into account the economic efficiency and environmental requirements for further operation, which is the basis for technical and economic assessments. Aim and tasks. This study aims to develop a technical and economic assessment of the safe operation of power equipment to ensure sustainable management of the remaining service lifespan. Results. An algorithm for assessing pipeline system elements by the coolant environment is proposed, which allows for the pipeline load and changes in erosion and corrosion caused by coolant movement. It was proposed that the equipment be systematised by safety class and coolant. When conducting a technical and economic assessment, these parameters and the costs of extending the service life and upgrading the existing equipment were considered in the standard calculations of a certain type of equipment. For this purpose, mathematical models for calculating the residual life for each type, obtained and confirmed based on empirical studies, are proposed. Research findings into ensuring the reliability and safety of operation with various heat carriers have shown that it is necessary to consider low-cycle and high-cycle loads and erosion processes. It was found that the erosive wear rate is 0.3-0.4 mm/year for bending sections of the main circulation pipeline, where maximum loads occur relative to low-cycle and vibration loads, and the stress is 212.5 MPa when assessing the residual life of 7 years. Conclusions. The cost-effectiveness of reassigning the service life is reasonable, as it does not require additional investment in upgrading or replacing equipment subject to annual technical diagnostics. The systematisation of pipelines, improved codifiers, lifespan assessment models, and algorithms for evaluating the remaining life under various loadings enhance the regulatory framework for safe nuclear power plant operations and support technical and economic evaluations for extending their lifespan.

Diagnostics of prestressed ropes after multiannual operation – Bridge SNP Bratislava

AbstractBridges, as public structures, are national infrastructure structures. The investment requirements and demands for safe operation should put them at the forefront of engineers' attention. The important SNP bridge in Bratislava (Slovakia), which is one of the first bridges in the world to be suspended entirely on cables, has been the subject of a diagnosis of its health after 50 years of operation. The article describes and documents the individual steps of this diagnostics ‐ identification of the rope material, the status of the rope material and its current strength properties, and the experimentally and computationally determination of the forces in the individual ropes and their cables. The uniqueness of all the diagnostic steps was that they were carried out directly in the outdoor conditions of full operation of the bridge. The achieved results are briefly documented in the paper. Conclusions and further necessary steps for the final comprehensive safety assessment of the bridge operation are formulated.

Detection and Assessment of Seismic Response of High-Speed Railway Bridges Based on Smartphone Public Participation

The seismic response detection and operational safety assessment of high-speed railway (HSR) bridges play a crucial role in ensuring HSR systems’ operational safety and reliability. Smartphones have introduced intelligent inspection tools for structural health detection, becoming a new tool for intelligent structural inspection. Combining the public and smartphones is the key to public participation in structural health detection. This study utilizes smartphone-based structural seismic response inspection technology to investigate the framework of public participation in earthquake response inspection and assessment. This system comprises the Smart Bridge Brain (SBB), which integrates data from multiple sources and systems, an assigning mechanism for public participation inspection tasks, and smartphone-based HSR bridge structural seismic response inspection technology. At the same time, the Unreal Engine 5.0 software is used to create a mixed-reality virtual simulation experimental environment to validate the feasibility of this framework. The results indicate that the intelligent optimization of task allocation by the SBB successfully assigns detection tasks to each public participant. Public participants can promptly reach predefined damage structure detection targets and rapidly inspect bridge structural seismic response indicators using smartphones. In addition, this paper also conducts a comprehensive evaluation and analysis of the detection of the work efficiency index (WEI) within the system. Furthermore, optimization strategies for the efficient execution of detection tasks are proposed based on WEI variations influenced by different factors. The system framework is expected to enhance cluster-based HSR bridges’ intelligent disaster prevention and mitigation capabilities.

In-situ measurements of contact evolution for fractal rough surfaces under normal compression

The contact interface plays a key role in the overall functionality and stability of structures. Understanding the evolution of the contact interface over time and its dependency on materials and load is crucial for functional integrity and operational safety assessment. In this study, we employ in-situ three-dimensional X-ray computed tomography (3DXRCT) to examine the creep behavior of 3D-printed surfaces exhibiting various roughness under constant normal compression. We observe that the overall contact area enlargement during the contact creep decreases with roughness amplitude and fractal dimension. The variation of interfacial separation distance is found to increase with roughness amplitude and decrease with fractal dimension. Correlation analysis reveals that the microcontact size played a more important role than the asperity shape in determining the microcontact enlargement. By examining the calculated interfacial strains extracted from XRCT measurements, significant deformations are found to occur at the non-contacting zones, indicating strong asperity interactions. This study offers high-resolution experimental measurements and unravels the asperity micromechanics for contact creep on rough surfaces, providing insights into understanding and optimizing the performance of rough interfaces.

Evaluation of wind-induced turbulence around offshore platforms in different wind speeds and directions, along with safety assessment of helicopter operation and helideck’s air-gap optimization

The demand for helicopter transportation has increased as offshore activity has expanded into more remote waters. In this situation, safe takeoffs, approaches, and landings on the platform's helidecks require understanding wind behavior. This study simulates the effect of a helideck air gap on wind turbulence around an offshore platform. The simulations are carried out using a validated computational fluid dynamics model based on the Reynolds-averaged Navier-Stokes k-equations. Five wind directions (with intervals of 45°), two wind speeds (5, 15, and 35 m/s, respectively, for winds with 7-days, 1-year, and 100-year return periods), and six air gap sizes (0–6 m) were assumed to calculate the induced turbulence. The Norsok C-004 standard, two speed-base, and one energy-based criterion were used to identify the turbulence conditions that allow helicopter operations. Wind-induced turbulence was significantly generated by the interaction of the wind with the crane and equipment placed on the highest level, limiting helicopter operation, particularly in most cases where the wind blows from the southwest. According to the findings, a minimum 4-m air gap is nedded to reduce turbulence caused by wind contact with equipment. Although no upward or downward flows (with ±2 m/s) have formed on the helipad, they have formed strongly around the helipad structure and in the direction of the helicopter approach.

Digital twin modeling and intelligent optimization for rail operation safety assessment

Currently, the use of fixed empirical parameters combined with traditional algorithms to construct train parameter prediction models for estimating train energy consumption is often used. However, due to changes in train related parameters, there is a significant error between the estimated results of this method and the actual values, which cannot reflect the true state of train operation. It affects the subsequent maintenance and repair of trains, thereby affecting the safety of the entire subway operation system. To address the above issues, a train traction power flow model based on digital twin technology is proposed. The swarm intelligence optimization algorithm is not used to correct model parameters. By correcting the deviation of train passenger load, accurate prediction of train energy consumption can be achieved. The experimental results show that the power flow model constructed by the research institute can reduce the power error of single interval trains by over 11.91%. The average DC voltage error of the train power flow model after parameter correction is 0.19%. The average DC current error is 12.07%. The root mean square error range of passenger capacity for similar day neural network models is [0.0521,0.0811]. The experimental results indicate that the model constructed by the research institute can accurately predict train energy consumption and ensure the safety of the subway operation system.

Research on the influence of the connection and withdrawal of a 35 kV bypass system on the power quality of transmission lines

Uninterrupted power supply maintenance has become a trending issue with the increasing reliability requirements for 35 kV power transmission. The bypass operation holds significant importance in 10 kV and 100 kV power transmission maintenance. However, research on live maintenance of a 35 kV bypass system remains scarce and requires urgent supplementation. Therefore, this paper aims to determine the feasibility of live operation for the 35 kV bypass system by studying the impact of its connection and disconnection on the voltage and current of the transmission lines. The existing 35 kV bypass live maintenance system is analyzed and studied concerning the operational process. When the bypass system is connected or disconnected during the maintenance of transmission lines, it may cause changes in the voltage and current, which could affect the safety of power transmission. To address this phenomenon, the paper performs calculations and analysis for different scenarios, including moments of varying voltage amplitudes in the lines and different maintenance cable lengths in the bypass system. Through theoretical analysis and simulation, a comprehensive study of voltage and current variations in two different scenarios of transmission lines has been conducted during the simulation process, including equivalent capacitance and initial conditions for the transmission lines and bypass systems, enabling the simulation of the switching process. Based on calculations and analysis, this paper presents a safety assessment of live operation in the 35 kV bypass live maintenance system.

Surrogate Safety Assessment of One-Way Operation

Surrogate Safety Assessment of One-Way Operation

Comprehensive Review of Safety Studies in Process Industrial Systems: Concepts, Progress, and Main Research Topics

This paper focuses on reviewing past progress in the advancement of definitions, methods, and models for safety analysis and assessment of process industrial systems and highlighting the main research topics. Based on the analysis of the knowledge with respect to process safety, the review covers the fact that the entire system does not have the ability to produce casualties, health deterioration, and other accidents, which ultimately cause human life threats and health damage. And, according to the comparison between safety and reliability, when a system is in an unreliable state, it must be in an unsafe state. Related works show that the main organizations and regulations are developed and grouped together, and these are also outlined in the literature. The progress and current research topics of the methods and models have been summarized and discussed in the analysis and assessment of safety for process industrial systems, which mainly illustrate that the dynamic operational safety assessment under the big data challenges will become the research direction, which will change the future study situation.

Can the Orbital Debris Disease Be Cured Using Lasers?

Ground-based high-power lasers are, in principle, able to de-orbit any kind of space debris object from the low Earth orbit (LEO) by remotely inducing laser-ablative momentum. However, the assessment of efficiency and operational safety depends on many factors, like atmospheric constraints or the risk of debris disintegration during irradiation. We analyze laser momentum for a great variety of target geometries and sizes and—for the first time in a large-scale simulation—include thermal constraints in the laser irradiation configuration. Using a coherently coupled 100 kJ laser system at 1030 nm wavelength and a 5 ns pulse duration in an optimized pointing elevation angle range, the pulse frequency should amount to less than 10 Hz to prevent fragment meltdown. For mechanically intact payloads or rocket bodies, repetition rates should be even lower. Small debris fragments sized between 10 and 40 cm can be de-orbited by employing around 100 to 400 station passes with head-on irradiation, while objects exceeding 2 m typically require far more than 1000 irradiations for de-orbit. Hence, laser-based debris removal cannot be considered a prime space sustainability measure to tackle the highest-risk large debris, yet it can provide the remediation of a multitude of small-sized debris using small networks of globally distributed laser sites.

Model-based Operation Safety Assessment for Civil Aircraft

With the operation of China’s large aircraft, operational safety has become an important issue. The manufacturer uses operation data and design data to carry out safety assessments in the operation phase. Operation safety assessment evaluates whether the conclusion of the safety assessment is still valid and analyzes the safety margin of the aircraft in the operating environment. Model-based civil aircraft operation safety assessment method uses the model-based ideology to propose a technical method of operating safety assessment based on the failure propagation model. The relevant practice also shows that this method is effective and can improve efficiency and accuracy.

Review of Inaccuracies in the Analysis of the Flow Stability Specific of the LW-SMR Modular Design

The presented analysis has been issued to express doubts about the correctness of the engineering and operational safety assessment, which arises from the modeling of transient modes and methodologically should help light water small modular nuclear reactor designers/developers to correct the model they are usually creating for studying the stability of the thermal-hydraulic circuit of the light water small modular nuclear reactor with the natural circulation of primary coolant. After the NuScale report publication and the following presentation review, additional questions arise regarding the analysis methodology, which was carried out and presented as part of the licensing package presented to NRC. After having carefully and critically read the available part of the presented report on the study of instabilities and the presentation issued by NuScale, the answer to the NRC safety committee request could be concluded that the instability analysis has not been performed correctly not only technically, but theoretically. Some clarification of the problem of analysis of instabilities is required additional explanations for further integral light water small modular nuclear reactor design developments and correct analysis implementations.

A System Safety Assessment (SSA) of the Maritime Air Rescue Operation of the Philippine Coast Guard (PCG)

A System Safety Assessment (SSA) of the Maritime Air Rescue Operation of the Philippine Coast Guard (PCG)

Risk Analysis for Train Collisions Using Fault Tree Analysis: Case Study of the Hanoi Urban Mass Rapid Transit

The urban mass rapid transit (UMRT) Line HN2A is the first light rail transit line in Vietnam. It is also the first time the operational safety assessment for the whole life cycle of a railway project is applied and assessed by an applicable scientific tool. While various industry standard methods have been deployed in many countries, their application is not appropriate for assessing the outdated railway infrastructure in Vietnam. This article proposes a method for generating safety risk models for train collisions using the fault tree analysis (FTA) technique. The FTA method comprehensively evaluates the fundamental error and failure probability that could potentially lead to accidents in general and train collisions in particular on Line HN2A. The study describes the procedure for establishing FTA and determining assumptions based on technical specifications and similar railway systems. Compared with the statistical failure results using data from operational tests and commissioning (2018–2021) of the metro line, the results here indicate that this is a reasonable theoretical model applicable to UMRT in Vietnam. The theoretical model will be processed to generate the first-ever scientific risk assessment system based on empirical evidence. In addition, real-time accident and operation data will continue to be collected and compared to the theoretical model to improve its accuracy. The findings of this study could serve as a starting point for risk management on current and future freight, passenger, and metro lines in Vietnam.

Graphical safety assurance case using Goal Structuring Notation (GSN) — challenges, opportunities and a framework for autonomous trains

The development of fully autonomous vehicles is an ambition that took seed in the automotive industry a few years ago and is now growing in the railways considering their benefits. The main objective of autonomous train is to perform its operations and assure its mission with an acceptable safety level in all possible operational conditions. Such an objective needs to be supported by a safety demonstration. In order to authorize the operations of railway systems, they must be proven safe. This requires a technical and operational safety assessment, and also a safety assurance process during the system’s whole life-cycle. The goal of such activities is to ensure that designed systems comply with railway safety standards and regulations. Both safety arguments and evidences are required to demonstrate that this compliance is achieved. These sets of evidence are documented in a so-called safety case. Recently, graphical safety cases, such as Goal Structuring Notation (GSN)-based safety case, have become an interesting alternative to narrative reports and plain texts. The graphical structure and visual properties improve the presentation and comprehension of the safety arguments. In this paper, we firstly review the use of the GSN for building graphical safety case for different transportation systems, with a focus on the railway domain. Then, we discuss the opportunities and challenges of considering such an approach in railway and we propose a high-level framework for building the GSN-based safety assurance case for the autonomous trains.

Evaluation of the drone-human collision consequences

The operational safety assessment of the unmanned vehicles is crucial for their subsequent practical use. The safety limit criteria used for the operation assessment, especially values closely related to the safety of persons and their vulnerability to collision with these vehicles, represent nowadays a significant limitation. This contribution presents the currently discussed and proposed human safety criteria for the UAS, evaluates the available data from the collision dynamic tests and computer modelling and provides the possibility to compare and evaluate these criteria on a validated set of data. A total of five small UAS, three multi-rotor quadcopters and two fixed-wing aircrafts were used to verify the current methods and serve as a basis for the assessment. The results of the measurements obtained through the crash tests demonstrate the excessive restrictiveness of the currently used kinetic energy threshold values and the limited value of some proposed criterions, e.g. the blunt criterion. On the contrary, they point to the appropriateness of the application of car vulnerability criterions. The UAS mass or kinetic energy tests represent an easily definable threshold value, however, the available data sets and the tests performed showed limitations of its applicability for the deformable and fragile UAS structures. The article aims to verify, based on its own impact tests, the adequacy of the evaluation of the safety criteria of the UAS operation in relation to the development of the current legislation that defines the conditions of use of these machines.

Probabilistic Collapse Design and Safety Assessment of Sandwich Pipelines

This paper presents an approach for probabilistic design and safety assessment of sandwich pipelines under external pressure. The methodology consists of the categorisation of sandwich pipeline collapse strength models based on interlayer adhesion conditions. The models are validated by comparing their predictions against collapse test data of sandwich pipelines. The accuracy of the strength models and their prediction uncertainty are used to select the best model in each category. Regarding interlayer adhesion categories, uncertainty propagation of models’ predictions over a wide range is assessed by the Monte Carlo simulation method. The proposed methodology is demonstrated using a case study of a sandwich pipeline with adequate probabilistic modelling of the basic random variables. Different limit states are defined for three categories of sandwich pipelines, based on which structural reliability indices are estimated. In employing the First Order Reliability Method for sensitivity analysis, the importance of basic variables of the limit states is evaluated. Later, a parametric analysis is conducted, presenting reliability variations for several design and operational scenarios of sandwich pipelines. Finally, to achieve a uniform level of structural reliability of sandwich pipelines, a few suggestions are provided, and practical partial safety factors are calculated. The results of the present analysis can provide guidance on the probabilistic design and operational safety assessment of sandwich pipelines.

Operational safety assessment of straddle-type monorail vehicle system based on cloud model and improved CRITIC method

This paper proposes an improved critic method and establishes an operational safety assessment method for straddle-type monorail vehicle system based on cloud model and improved critic method. Firstly, according to the structure and function of straddle- type monorail vehicle system, the reliability index system of straddle-type monorail vehicle is established, and the weight value of reliability evaluation index is determined by improved critic method. Then, the cloud model expression of reliability evaluation index of straddle-type monorail vehicle system is obtained by virtual cloud. finally, similarity analysis is conducted between the new cloud of straddle-type monorail vehicle system reliability comprehensive index and the cloud model of reliability evaluation set, so as to judge that the comprehensive cloud model of straddle-type monorail vehicle system can be used to evaluate the operation status of “main functions” of the system. The analysis shows that the reliability evaluation method of straddle-type monorail vehicle system based on cloud model and improved critic method can correctly describe the daily operation of straddle-type monorail vehicle system in Chongqing, which provides a method reference for reliability evaluation of straddle-type monorail vehicle system.