Impact of Improving Design Factor over 0.72 on the Safety and Reliability of Gas Pipelines and Feasibility Justification

Many years experience of the operation of high stress (>72% specified minimum yield strength, SMYS) gas pipelines and statistical analysis results of pipeline incidents showed that the operating pipelines at stress levels over 72% SMYS have not presented problems in USA and Canada, and design factor does not control incidents or the safety of pipelines. Enhancing pipeline safety management level is most important for decreasing incident rate. The application history of higher design factors in the U.S and Canada was reviewed. And the effect of higher factors to the critical flaw size, puncture resistance, change of reliability with time, risk level and the arrest toughness requirements of pipeline were analyzed here. The comparison of pipeline failure rates and risk levels between two design factors (0.72 and 0.8) has shown that a change in design factor from 0.72 to 0.8 would bring little effect on failure rates and risk levels. On the basis of the analysis result, the application feasibility of design factor of 0.8 in China was discussed and the related suggestions were proposed. When an operator wishes to apply design factor 0.8 to gas pipeline, the following process is recommended: stress level of line pipe hydro test should be up to 100% SMYS, reliability and risk assessment at the design feasibility or conceptual stage should be conducted, Charpy impact energy should meet the need of pipeline crack arrest; and establish and execute risk based integrity management plan. The technology of pipeline steel metallurgy, line pipe fabrication and pipeline construction, and line pipe quality control level in China achieved tremendous progresses, and line pipe product standards and property indexes have come up to international advanced level. Furthermore, pipeline safety management has improved greatly in China. Consequently, the research for the feasibility of application of design factor of 0.8 in China has fundamental basis.

A New Safety Assessment Method Based on Belief Rule Base With Attribute Reliability

Safety assessment is one of important aspects in health management.In safety assessment for practical systems,three problems exist:lack of observation information,high system complexity and environment interference.Belief rule base with attribute reliability(BRB-r)is an expert system that provides a useful way for dealing with these three problems.In BRB-r,once the input information is unreliable,the reliability of belief rule is influenced,which further influences the accuracy of its output belief degree.On the other hand,when many system characteristics exist,the belief rule combination will explode in BRB-r,and the BRB-r based safety assessment model becomes too complicated to be applied.Thus,in this paper,to balance the complexity and accuracy of the safety assessment model,a new safety assessment model based on BRB-r with considering belief rule reliability is developed for the first time.In the developed model,a new calculation method of the belief rule reliability is proposed with considering both attribute reliability and global ignorance.Moreover,to reduce the influence of uncertainty of expert knowledge,an optimization model for the developed safety assessment model is constructed.A case study of safety assessment of liquefied natural gas(LNG)storage tank is conducted to illustrate the effectiveness of the new developed model.

Safety reliability optimal allocation of food cold chain

This paper applied the safety reliability of food cold chain logistics to establish reliability allocation model for cold chain systems, designed optimization algorithms, and made a case analysis. By applying system reliability allocation principle, this article firstly built safety reliability allocation model of food cold chain logistics system without cost constraint based on the safety reliability model of food cold chain logistics system, and then it set up optimal decision- making model of food cold chain logistics system with cost constraint using the functional relationship between the time, temperature of cold chain logistics and logistics costs. Next, according to the characteristics of the model, a heuristic algorithm was proposed to allocate safety reliability of the system to each cold chain unit so as to achieve the goal of operatingcosts optimization subject to assurance ofoverall safety reliability of the cold chain system. Taking the safety impact factor of food cold chain unit as a weight, the article also deduced the equation of reallocation of safety reliability of food cold chain system. In the end, these models were used to optimize the allocation of safety reliability in an example of Sushi cold chain process. It provided a new thought and method to optimally plan the unit safety of food cold chain system as well as reduce the cost of food cold chain.

System Reliability Analysis of Offshore Strctures and Component Safety Rank Assessment

Offshore structures will encounter serious environmental load, so it is important to study the structural system reliability and to evaluate the structural component safety rank. In this paper, the bracnch-and-bound method is adopted to search the main failure path, and the Ditlevsen bound method is used to calculate the system failure probability. The structure is then assessed by the fuzzy comprehensive assessment method, which evaluates the structural component safety rank. The ultimate equation of the tubular cross- section is analyzed on the basis of ultimate stregnth analysis. The influence of effect coefficients on the structural system failure probability is investigated, and basic results are obtained. A general program for spatial frame structures by means of the above method is developed, and verified by the numerical examples.

The stability safety factor calibration based on the reliability index

When the bridge structure stability safety factor of the first type is 4, the research that whether the structure reliability index will reach target reliability index under the more-likely-to-happen collapse situation of the second type is necessary. The stability calculations of the first and the second type are made respectively for single layer and single span rigid frame bridge. Based on the critical load obtained from the stability calculation of the first type, the stability safety factor of the first type is taken as 4, and the first order reliability method is used to program and calculate the reliability index. Then, the load effect under the stability reliability index cal- culation of the first type and the critical load of the second type are employed to calculate the reliability index of the second type. The evaluation of structure stability safety factor is discussed according to reliability index. Based on the discussion above, parameter analysis of the stable critical loads of two types is made, and the in- fluence of critical load change on reliability index is researched. The result shows that stability analysis should identify collapse state; when the stability safety factor of the first type is 4, but the structure has the collapse of the second type, the reliability index cannot be ensured to reach the target reliability index under certain condi- tions.

Evaluation on Safety and Reliability of High-Pressure Vessel in Missile System

Through theoretical analysis of reliability and simulation analysis of dispersivi of d a/ d N based on Monte Carlo method, the distribution function of n and c was set up. Meanwhile, the distribution of critical opening displacement(COD)δ c was defined by the use of coherent coefficient method, and the probabilistic model of defects assessment of military special vessel was built. Thereby the theoretical and practical fundamental research on evaluation of reliability of military high pressure vessels was carried out.

Safety Level and Reliability Index for Bank Slope Stability

Based on statistics and analysis of the safety factor of unstable bank slopes, the relation between safety level and reliability index of stability is studied and discussed, and then the elementary calibrating calculation is carried out to the levels of safety and reliability for bank slope stability in the range of safety factors stipulated in existing China Technical Specifications for Port Engineering - Foundation Part (1987) and to those reached by some stable bank slopes already built. The results show that the reliability index beta in the effective stress method is able to reach a high value of 2.4 similar to 4.1 (mid-value 3.25), while the value of beta in other three kinds of total stress method can just reach a lower value of 0.5 similar to 2.8 (mid-value 1.65), which are in conformity with the engineering experience in China, and thus acceptable. Some suggestions are also given in this paper to the adoption of the value of beta(0)-objective reliability index for bank slope stability.

Reliability Study on the Risk Precontrol Management System of Coal Mines Safety

Risk precontrol management system of coal mines safety( RPMSCS) provides a set of preventive safety management strategy for high-risk coal industries, which has captured extensive attentions. Fundamentally,there are several membership systems with subsystems in the management system, and the subsystem reliability has an important influence on the management system performance. Through analyzing the structure characteristics of the management system,the phase type distribution was employed to analyze its subsystem reliability by considering repair process and three states including working,fail-abnormal,and fail-emergency states. The reliability indices of the subsystem were derived respectively,including the probabilities that the subsystem in three states,mean time to the first failure, mean time to first failemergency,mean working time to first fail-emergency,and mean maintenance time to the first fail-emergency, are derived respectively. The probabilities of the membership systems and the management system in three states were also derived. Some numerical examples were used to show the procedures. The result is important for better understanding the management system operation and improving its operational performance from the respect of system reliability.

Handling Uncertainty in Human Cognitive Reliability Method for Safety Assessment Based on DSET

Human Reliability Analysis(HRA)is an important part in safety assessment of a large complex system.Human Cognitive Reliability(HCR)model is a method of evaluating the probability that operators fail to complete during diagnostic decision making within a limited time,which is widely used in HRA.In the application of this method,cognitive patterns of humans are required to be considered and classified,and this process often relies on the evaluation opinions of experts which is highly subjective and uncertain.How to effectively express and process this uncertain and subjective information plays a critical role in improving the accuracy and applicability of HCR.In this paper,a new model was proposed to deal with the uncertain information which exists in the processes of cognitive pattern classification in HCR.First,an evaluation panel was constructed based on expert opinions and processing including setting corresponding anchor points and qualitative indicators of different cognitive patterns,and mapping them to fuzzy numbers and unit intervals.Second,based on the evaluation panel,different analysts judge the cognitive pattern types of actual specific events and provide the level of confidence he or she has in the judgments.Finally,the evaluation opinions of multiple analysts were expressed and fused based on the Dempster-Shafer Evidence Theory(DSET),and the fused results were applied to the HCR model to obtain the Human Error Probability(HEP).A case study was used to demonstrate the procedure and effectiveness of the proposed method.

On Dual-Mode Driving Control Method for a Novel Unmanned Tractor With High Safety and Reliability

Due to the non-standardization and complexity of the farmland environment,it is always a huge challenge for tractors to achieve fully autonomy(work at Self-driving mode)all the time in agricultural industry.Whereas,when tractors work in the Tele-driving(or Remote driving)mode,the operators are prone to fatigue because they need to concentrate for long periods of time.In response to these,a dual-mode control strategy was proposed to integrate the advantages of both approaches,i.e.,by combing Self-driving at most of the time with Tele-driving under special(complex and hazardous)conditions through switching control method.First,the state switcher was proposed,which is used for smooth switching the driving modes according to different working states of a tractor.Then,the state switching control law and the corresponding subsystem tracking controllers were designed.Finally,the effectiveness and superiority of the dualmode control method were evaluated via actual experimental testing of a tractor whose results show that the proposed control method can switch smoothly,stably,and efficiently between the two driving modes automatically.The average control accuracy has been improved by 20%and 15%respectively,compared to the conventional Tele-driving control and Self-driving control with low-precision navigation.In conclusion,the proposed dualmode control method can not only satisfy the operation in the complex and changeable farmland environment,but also free drivers from high-intensity and fatiguing work.This provides a perfect application solution and theoretical support for the intelligentization of unmanned farm agricultural machinery with high safety and reliability.

Study of the Service Reliability of Machines Based on Safety

From the point of safety being the basic requirement of machine operation, equivalent failure number, which is employed to replace the actual statistical failure number, is introduced. Calculating theory of service reliability indexes of machines based on safety is developed. The method proposed in this paper can reflect the damage degree of failure.

Risk identification and safety assessment of human-computer interaction in integrated avionics based on STAMP

To solve the problem of risk identification and quantitative assessment for human-computer interaction(HCI)in complex avionics systems,an HCI safety analysis framework based on system-theoretical process analysis(STPA)and cognitive reliability and error analysis method(CREAM)is proposed.STPACREAM can identify unsafe control actions and find the causal path during the interaction of avionics systems and pilot with the help of formal verification tools automatically.The common performance conditions(CPC)of avionics systems in the aviation environment is established and a quantitative analysis of human failure is carried out.Taking the head-up display(HUD)system interaction process as an example,a case analysis is carried out,the layered safety control structure and formal model of the HUD interaction process are established.For the interactive behavior“Pilots approaching with HUD”,four unsafe control actions and35 causal scenarios are identified and the impact of common performance conditions at different levels on the pilot decision model are analyzed.The results show that HUD's HCI level gradually improves as the scores of CPC increase,and the quality of crew member cooperation and time sufficiency of the task is the key to its HCI.Through case analysis,it is shown that STPACREAM can quantitatively assess the hazards in HCI and identify the key factors that impact safety.

Reflection on methodology of the correlation between electromagnetic interference and safety in high-speed railway

Purpose – In the continuous development of high-speed railways, ensuring the safety of the operation controlsystem is crucial. Electromagnetic interference (EMI) faults in signaling equipment may cause transportationinterruptions, delays and even threaten the safety of train operations. Exploring the impact of disturbances onsignaling equipment and establishing evaluation methods for the correlation between EMI and safety isurgently needed.Design/methodology/approach – This paper elaborates on the necessity and significance of studying theimpact of EMI as an unavoidable and widespread risk factor in the external environment of high-speed railwayoperations and continuous development. The current status of research methods and achievements from theperspectives of standard systems, reliability analysis and safety assessment are examined layer by layer.Additionally, it provides prospects for innovative ideas for exploring the quantitative correlation between EMIand signaling safety.Findings – Despite certain innovative achievements in both domestic and international standard systems andrelated research for ensuring and evaluating railway signaling safety, there’s a lack of quantitative and strategic research on the degradation of safety performance in signaling equipment due to EMI. A quantitativecorrelation between EMI and safety has yet to be established. On this basis, this paper proposes considerationsfor research methods pertaining to the correlation between EMI and safety.Originality/value – This paper overviews a series of methods and outcomes derived from domestic andinternational studies regarding railway signaling safety, encompassing standard systems, reliability analysisand safety assessment. Recognizing the necessity for quantitatively describing and predicting the impact ofEMI on high-speed railway signaling safety, an innovative approach using risk assessment techniques as abridge to establish the correlation between EMI and signaling safety is proposed.

Human Error Model and Definition of Human Reliability

Aim A model of human errors is given. His reliability of action is also determined. Safety countermeasures to prevent human errors are put forward. Methods\ Human system is regarded as a maintainable Markov system. On the basis of Markov method, the deduction and calculation in practice are made. Results\ Human errors are the chief factors leading to accidents, and may appear in different models. There are two kinds of states the normal and error state in a process of work. The process of state transfer human system is a Markov process. Human action reliability will be decreased with the continuation of time. Conclusion\ Human errors are described in the quantified form. It will have some significance in terms of theory in the study of the relationship between human action and accidents. Thus helping us in the preven tion of accident occurrence. The safety of a system can be improved in this way.

FUZZY RELIABILITY-BASED OPTIMUM DESIGN OF LAMINATED COMPOSITES

In conventional reliability-based optimum design of structures, the reliability is computed based on the probability assumption, and the design objective and constraint are considered as deterministic ones. In many cases, however, there exist some fuzzy factors in the design objective and constraint functions. In this paper, the fuzzy reliability and fuzzy constraint are introduced to establish the fuzzy reliability-based optimum model for laminated composites. The examples show that the method developed in this paper can give consideration to both the reliability demand and the economic aspect of a structure. Since the fuzzy reliability-based optimum design is a ＇soft＇ design, the present results provide a new methodology for the effective evaluation of structural reliability and bring us an alternative optimum design idea.

Comparative Study on Structural Redundancy of Cable-Stayed and Extradosed Bridges Through Safety Assessment of Their Stay Cables

This study provides new insights into the comparison of cable-stayed and extradosed bridges based on the safety assessment of their stay cables.These bridges are often regarded as identical structures owing to the use of inclined cables;however,the international standards for bridge design stipulate different safety factors for stay cables of both types of bridges.To address this misconception,a comparative study was carried out on the safety factors of stay cables under fatigue and ultimate limit states by considering the effects of various untoward and damaging factors,such as overloading,cable loss,and corrosion.The primary goal of this study is to describe the structural disparities between both types of bridges and evaluate their structural redundancies by employing deterministic and nondeterministic methods.To achieve this goal,three-dimensional finite-element models of both bridges were developed based on the current design guidelines for stay cables in Japan.After the balanced states of the bridge models were achieved,static analyses were performed for different safety factors of stay cables in a parametric manner.Finally,the first-order reliability method and Monte Carlo method were applied to determine the reliability index of stay cables.The analysis results show that cable-stayed and extradosed bridges exhibit different structural redundancies for different safety factors under the same loading conditions.Moreover,a significant increase in structural redundancy occurs with an incremental increase in the safety factors of stay cables.

Reliability analysis for seismic stability of tunnel faces in soft rock masses based on a 3D stochastic collapse model

A new horn failure mechanism was constructed for tunnel faces in the soft rock mass by means of the logarithmic spiral curve. The seismic action was incorporated into the horn failure mechanism using the pseudo-static method. Considering the randomness of rock mass parameters and loads, a three-dimensional (3D) stochastic collapse model was established. Reliability analysis of seismic stability of tunnel faces was presented via the kinematical approach and the response surface method. The results show that, the reliability of tunnel faces is significantly affected by the supporting pressure, geological strength index, uniaxial compressive strength, rock bulk density and seismic forces. It is worth noting that, if the effect of seismic force was not considered, the stability of tunnel faces would be obviously overestimated. However, the correlation between horizontal and vertical seismic forces can be ignored under the condition of low calculation accuracy.

A Reliability Evaluation Method for Intermittent Jointed Rock Slope Based on Evolutionary Support Vector Machine

The randomness of rock joint development is an important factor in the uncertainty of geotechnical engineering stability.In this study,a method is proposed to evaluate the reliability of intermittent jointed rock slope.The least squares support vector machine(LSSVM)evolved by a bacterial foraging optimization algorithm(BFOA)is used to establish a response surface model to express the mapping relationship between the intermittent joint parameters and the slope safety factor.The training samples are obtained from the numerical calculation based on the joint finite element method during this process.Considering the randomness of the intermittent joint parameters in the actual project,each parameter is evaluated at different locations on the site,and its distribution characteristics are counted.According to these statistical results,a large number of parameter combinations are obtained through Monte Carlo sampling.The trained machine learning mapping model is used to obtain the slope safety factor corresponding to each group,and these results are then used to obtain the slope reliability.When the research results were applied to slope disaster treatment along the Yalu River in China’s Jilin Province,it was found that the joint length and joint inclination angle both play key roles in rock slope stability,which should receive more attention in the slope treatment.In summary,this study establishes a method for evaluating the reliability of intermittent jointed rock slope based on an evolutionary SVM model,and its feasibility is verified by engineering application.

A Safe and Reliable Heterogeneous Controller Deployment Approach in SDN

Software-Defined Networking(SDN)provides flexible and global network management by decoupling control plane from data plane,and multiple controllers are deployed in the network in a logically centralized and physically distributed way.However,the existing approaches generally deploy the controllers with the same type in the network,which easily causes homogeneous controller common-mode fault.To this end,this paper proposes heterogeneous controller deployment in the SDN,considering the different types of controllers and relevant criteria(e.g.,delay,control link interruption rate,and controller fault rate).Then,we introduce a Safe and Reliable Heterogeneous Controller Deployment(SRHCD)approach,consisting of two stages.Stage 1 determines the type and the number of heterogeneous controllers required for the SDN network based on the dynamic programming.Stage 2 divides the SDN network into multiple subnets by k-means algorithm and improves the genetic algorithm to optimize the heterogeneous controller deployment in these SDN subnets to ensure reliable switch-controller communications.Finally,the simulation results show that the proposed approach can effectively reduce the control plane fault rate and increase the attack difficulties.Besides,the switch-controller delay has been lowered by 16.5%averagely.

Finite element model with imposed slip surfaces for earth mass safety evaluation

The study of earth masses requires numerical methods that provide the quantification of the safety factor without requiring detrimental assumptions. For that, equilibrium analysis can perform fast computations but require assumptions that limit its potentiality. Limit analysis does not require detrimental assumptions but are numerically demanding. This work provides a new approach that combines the advantage of both the equilibrium method and the limit analysis. The defined hybrid model allows probabilistic analysis and optimization approaches without the assumption of interslice forces. It is compared with a published case and used to perform probabilistic studies in both a homogeneous and a layered foundation. Analyses show that the shape of the density probability functions is highly relevant when computing the probability of failure, and soil elasticity hardly affects the safety of factor of the earth mass.