Performance-based Safety Research Articles

Dynamic reliability and seismic fragility analysis for high concrete-faced rockfill dam slopes subjected to stochastic earthquake and parameter excitation via PDEM

The randomness of material parameters and earthquake excitation greatly impacts the seismic stability of high concrete-faced rockfill dam (CFRD) slopes. However, no research has comprehensively analyzed the impacts of stochastic earthquake excitations, random parameters and their coupled effects on seismic stability of CFRD slopes and selected a multi-indicator evaluation criterion to carry out performance-based safety assessment. This paper develops a novel and comprehensive framework for evaluating the seismic stability of CFRD slopes based on the generalized probability density evolution method (GPDEM) with high efficiency and accuracy. The effects of three kinds of randomness on seismic stability of CFRD slopes were comprehensively compared and analyzed on the basis of multi-indices (safety factor (FS), cumulative slip displacement and cumulative time with FS < 1.0). Firstly, the nonlinear shear strength parameters of 40 high CFRDs were statistically collected to obtain the statistical characteristics of rockfill material strength parameters of actual CFRD projects. Secondly, three kinds of random samples were generated using generalized F-discrepancy (GF-discrepancy) method and Spectral expression-Random function (SERF) method. Then, the GPDEM was introduced to combine with three indices to perform the stochastic analysis and reliability evaluation. Finally, the fragility analysis of the CFRD slope was conducted. The results reveal that FS is more sensitive to the ground motions randomness, while cumulative slip displacement and cumulative time with FS < 1.0 are more sensitive to the material parameters randomness. The seismic safety evaluation of CFRD slopes based on multiple indices with full consideration of coupled randomness effects is necessary.

Study on the Analysis of Pile Foundation Deformation and Control Methods during the Excavation of Deep and Thick Sludge Pits

This study aims to apply performance-based safety-assessment methods to the monitoring and numerical simulation of excavation engineering projects in order to comprehensively enhance engineering risk management and decision support. In this paper, a deep excavation project in Hefei with thick silty clay layers was studied. The analysis included the surface settlement, the deformation of support structures, the vertical and horizontal displacements of pile tops, axial forces in steel braces, settlement, and the horizontal displacement of a gravity retaining wall on the south side of the excavation using field-monitoring data. A refined three-dimensional finite element model was established to further analyze the distribution of uplift displacement at the bottom of the excavation, horizontal displacement, and bending moments of piles based on simulation results. The research findings indicate that phased excavation can reduce the spatial extent of disturbance to the surrounding soil caused by excavation. Additionally, the closer the location to the excavation and the thicker the underlying silty clay layer, the faster the rate of settlement change and the greater the surface settlement. The spatial structure formed by steel braces and pile foundations effectively reduced the horizontal displacement of the engineering piles. The study’s use of field monitoring and finite element simulation provided valuable insights into the deformation of support structures and the response of the surrounding soil to excavation, confirming the rationality and applicability of the support structure in this paper. The proposed method can serve as a reference for similar complex stratum excavation design and construction. The performance-based safety assessment is introduced, and the monitoring data, numerical simulation results, and performance targets are comprehensively analyzed to provide a reliable scientific basis for engineering decision making.

Autonomous vehicles and street design: Exploring the role of medians in enhancing pedestrian street crossing safety using a virtual reality experiment

As traffic lanes and on-street parking spots can potentially be downsized with the introduction of autonomous vehicles (AVs), the possibility of additional spare road space becoming available arises in future urban streets. While discussions on converting the leftover space into pedestrian-friendly alternatives exist, allocating that limited space to which alternative is foreseen to be another practical issue shared in both urban and transportation planning. However, evidence-based guidance on the issue provided from the actual verification on whether or to what extent the proposed alternatives may have an effect seems to be absent. Therefore, with an emphasis on pedestrian safety, this study focused on the “median strip” alternative as a first example and, through a VR simulation experiment aimed at empirically examining its suggested role on enhancing street crossing safety and further exploring its possible influence on pedestrians’ trust toward autonomous driving. With 99 participants, perceived safety (individual assessments of safety), performance-based safety (crossing success/abandonment and collision occurrence), and trust were either questioned or recorded for nine scenarios with varying crossing conditions. A combination of multilevel models and cross-tabulation results indicate that medians seem especially significant in ensuring the performance-based safety results of pedestrians even when AVs are driving at high speeds or with smaller gaps, thus suggesting it a win–win option for both. Insights and implications on the role and management of medians in future streets are further provided.

A Predictive Approach to Identify Geometrically Hazardous Road Segments and Evaluate the Relative Safety Effects of Design Alternatives

This study has two goals: First, to fill a gap in the use of the predictive approach for evaluating road safety performance in Ethiopia, the most recent analytical methods of the HSM predictive approach in IHSDM software were used to evaluate the safety and operational effects of the existing roadway geometric design. Second, to assure safety and a sustainable transportation system, the relative safety effects of design changes made to hazardous road segments were quantified. Based on the Crash Prediction Module (CPM) evaluation of IHSDM software, the study identified fifteen hazardous road segments on the existing rural two-lane roads of Addis Ababa to Chacha and Addis Ababa to Dillela. The design changes made to the hazardous road segments have resulted in a remarkable reduction in crash rate, especially on the first top five hazardous segments, where incredible improvements have been observed. The total safety benefits acquired by applying engineering mitigations to the fifteen identified hazardous segments are described as follows: 17.18% reduction in total crash frequency (crashes/year), 58.94% reduction in crash rate (crashes/km/year), and 58.86% reduction in travel crash rate (crashes/million veh-km). In general, the study’s findings underlined the effectiveness of performance-based road safety evaluation and design in providing safe, efficient, and economically-feasible roadway infrastructure. The IHSDM reports and graphical outputs assist decision-making in the roadway design process by providing a quantitative evaluation of the safety impact of various design features and identifying roadway segments with safety concerns. Additionally, IHSDM is a tool capable of saving time for Road Safety Audit (RSA) teams. The paper also outlined the need for a computerized crash database recording system in Ethiopia to develop jurisdiction-specific Safety Performance Functions (SPFs).

Record-to-record variability and code-compatible seismic safety-checking with limited number of records

The Italian code requires spectrum compatibility with mean spectrum for a suite of accelerograms selected for time-history analysis. Although these requirements define minimum acceptability criteria, it is likely that code-based non-linear dynamic analysis is going to be done based on limited number of records. Performance-based safety-checking provides formal basis for addressing the record-to-record variability and the epistemic uncertainties due to limited number of records and in the estimation of the seismic hazard curve. “Cloud Analysis” is a non-linear time-history analysis procedure that employs the structural response to un-scaled ground motion records and can be directly implemented in performance-based safety-checking. This paper interprets the code-based provisions in a performance-based key and applies further restrictions to spectrum-compatible record selection aiming to implement Cloud Analysis. It is shown that, by multiplying a closed-form coefficient, code-based safety ratio could be transformed into simplified performance-based safety ratio. It is shown that, as a proof of concept, if the partial safety factors in the code are set to unity, this coefficient is going to be on average slightly larger than unity. The paper provides the basis for propagating the epistemic uncertainties due to limited sample size and in the seismic hazard curve to the performance-based safety ratio both in a rigorous and simplified manner. If epistemic uncertainties are considered, the average code-based safety checking could end up being unconservative with respect to performance-based procedures when the number of records is small. However, it is shown that performance-based safety checking is possible with no extra structural analyses.

A Numerical Analysis of the Fire Characteristics after Sprinkler Activation in the Compartment Fire

Understanding fire characteristics under sprinkler spray is valuable for performance-based safety design. However, fire characteristics during fire suppression by sprinkler spray has seldom been studied in detail. In order to present a fire suppression model by sprinkler spray and determine the fire characteristics after sprinkler activation in a compartment, a numerical analysis was conducted using a fire dynamics simulator (FDS). A simple fire suppression model by sprinkler spray was calibrated by comparing ceiling temperatures from experimental data. An extinguishing coefficient of 3.0 was shown to be suitable for the fire suppression model. The effect of sprinkler spray on the smoke layer during fire suppression was explained, revealing a smoke logging phenomenon. In addition, the smoke, which spread under the influence of the sprinkler spray, was also investigated. The temperature, velocity, and mass flow rate of the smoke layer through the doorway was significantly reduced during fire suppression compared to a free burn case.

B-737 MAX and the crash of the regulatory system

The FAA is looking to develop streamlined launch and reentry licensing requirements for the evolving commercial space industry. A central goal is to move from prescriptive requirements to performance requirements. By focusing on outcomes, performance standards give to developers flexibility and make it possible to find lowest-cost means to achieve compliance. Performance standards can generally accommodate technological change and the emergence of new technology driven hazards in ways that prescriptive standards cannot. However, how performance standards are designed and how they are implemented and enforced matters greatly. This paper uses the case of the Boeing B-737 MAX MCAS certification to illustrate the following mistakes to be avoided when using performance-based safety requirements: excessive trust on quantitative performance requirements, inadequate risk-based design process, and lack of independent design verification by experts.

Safety Evaluation of Geometric Design Criteria: Intersection Sight Distance at Unsignalized Intersections

A Policy on Geometric Design of Highways and Streets, 6th Edition, (publisher: AASHTO), provides design criteria for minimum sight distances, including intersection sight distance (ISD). An understanding of the relationship between ISD and safety at stop-controlled intersections is needed, with potential applications of this knowledge to both performance-based design and substantive road safety management practices. To establish this relationship, crash, traffic, and geometric data were collected from 832 two-lane minor unsignalized intersection approaches in Ohio, and Washington. The data were analyzed using a cross-sectional study design to quantify the relationship between safety and ISD. The analyses indicated that the expected number of target crashes are associated with available ISD. Target crash frequencies increase as available ISD decreases. Results suggest that ISD is associated with expected crash frequency in a non-linear fashion. The sensitivity of the expected number of target crashes to changes in ISD is highest when ISD is shorter, and decreases as ISD increases (i.e., the safety benefit of increasing ISD from 300 to 600 ft is substantially larger than the safety benefit of increasing ISD from 1,000 to 1,300 ft). The results also suggest that the impacts of ISD on crash frequencies vary as a function of the major road two-way annual average daily traffic and the major road speed limit. The sensitivity of the expected number of crashes to changes in ISD increases as both traffic volume and speed limit increase. Crash modification functions for each of the target crash types were estimated using the regression models.

Integrating operational and risk information with system risk models in air traffic control

The next generation Air Transport Management (ATM) requires performance-based safety management that is fully integrated into seamless operational management. To realize this objective, a framework is proposed in this article that structures risk information on ATM consoles in terms of four design principles: (i) integrating operational and safety-related data, (ii) managing interactions and minimizing transfer of risks to other sectors, (iii) generating risk patterns from accumulated experience and (iv) managing resources and safety barriers. The framework is applied to an approach control unit of a regional airport for the design of a performance dashboard that is linked to a safety module for managing hazards and safety barriers. In this sense, safety management is not an additional task to normal operations since risk information is integrated with operational data on a daily basis. Furthermore, the safety module combines traditional elements of bow-ties with new safety indices such as complexity metrics and risk patterns.

Developing Analytical Procedures for Calibrating the Highway Safety Manual Predictive Methods

Performance-based safety goals and objectives are more attainable with the use of the Highway Safety Manual (HSM). However, the safety performance functions (SPFs) in the HSM may not be accurate when used with local jurisdictions. Each SPF and crash modification factor (CMF) assume a set of base site conditions that might not be realistic or representative of local highways. The calibration procedures provided in Part C, Appendix A, of the HSM should therefore be modified to accommodate local data availability as well as roadway, traffic, and crash characteristics. Furthermore, a set of base conditions applicable to local highways should be determined. Results show that the HSM models underestimate the total average number of crashes on highway segments for all rural highway facility types in South Dakota. To quantify highway safety performance better, this study analyzed the underlying factors contributing to the underestimation and proposed procedures to improve crash prediction accuracy. The HSM calibration was performed with crash data from rural two-lane, two-way highways and rural multilane divided and undivided highways during a 5-year period (2008–2012). The procedures included establishing new base conditions, developing jurisdiction-specific SPFs, and converting CMFs to new base conditions. The comparison results show that the customized models outperform the HSM models in predicting sites with crashes.

A Study on the Improvement of Domestic Evacuation Safety Assessment through Case Analysis

Recently buildings have undergone many changes with more high-rise, larger and more complex structures being developed. All over the world, safety designs for buildings are being established through a variety of experiments and analysis of the planning and design stage of a comprehensive and scientific performance-based safety design for evacuation. In this study, this study seeks to present development directions for criteria related to domestic evacuation safety assessment through case studies. As a results, it is necessary to develop simulation programs as well as fire and evacuation scenarios that reflect domestic characteristics such as human behavior characteristics and space and occupants’ speed of movement so that appropriate performance-based design can be established. In addition, as the evacuation safety assessment-related standards are being manifested in building law and fire prevention regulations, it is determined that the need to develop integrated codes is immediate.

A system of safety management practices and worker engagement for reducing and preventing accidents: An empirical and theoretical investigation

ObjectiveThe overall research objective was to theoretically and empirically develop the ideas around a system of safety management practices (ten practices were elaborated), to test their relationship with objective safety statistics (such as accident rates), and to explore how these practices work to achieve positive safety results (accident prevention) through worker engagement. MethodData were collected using safety manager, supervisor and employee surveys designed to assess and link safety management system practices, employee perceptions resulting from existing practices, and safety performance outcomes. ResultsResults indicate the following: there is a significant negative relationship between the presence of ten individual safety management practices, as well as the composite of these practices, with accident rates; there is a significant negative relationship between the level of safety-focused worker emotional and cognitive engagement with accident rates; safety management systems and worker engagement levels can be used individually to predict accident rates; safety management systems can be used to predict worker engagement levels; and worker engagement levels act as mediators between the safety management system and safety performance outcomes (such as accident rates). ImplicationsEven though the presence of safety management system practices is linked with incident reduction and may represent a necessary first-step in accident prevention, safety performance may also depend on mediation by safety-focused cognitive and emotional engagement by workers. Thus, when organizations invest in a safety management system approach to reducing/preventing accidents and improving safety performance, they should also be concerned about winning over the minds and hearts of their workers through human performance-based safety management systems designed to promote and enhance worker engagement.

Study on Performance-based Safety Design of Chemical Facility Layout

At present, the design of chemical facility layout is always based on kinds of indicated codes, e.g. GB50160-2008 and GB50016-2006. There are many shortcomings of these codes, such as inflexible, lacking of comprehensive safety theory and ambiguous when applying to extra-large scale chemical plant and pilot plant. A performance-based framework was built for the safety design of chemical facility layout, which contains four key components: hazard identification, performance target confirmation, consequence assessment and defending effect evaluation. As the most important component of the framework, performance target confirmation was analyzed in particular, and a confirmation method was proposed through matching accident scenario and acceptable damage level of chemical facility.

Structuring critical success factors of airline safety management system using a hybrid model

With the global trend of legal requirement for a performance-based Safety Management System (SMS), to develop and implement an SMS to deliver services has become the most important goal within the airline industry. Yet there found some discrepancies concerning the use and the manner that SMS was being explained and taught. Therefore, this research aims to develop a quantitative evaluation model, which identifies the key components of airline SMS and considers the interaction between key components. To explore the core value of SMS, an extensive review regarding SMS components are firstly conducted and summarized from major aviation organizations and authorities, and then Grey Relational Analysis is used to group and select key components. After the critical components are derived, Decision Making Trial Evaluation Laboratory and Analytic Network Process are employed to analyze and map out all kinds of interactions among critical components and dimensions systematically. An empirical study is presented to illustrate the application of the proposed methods. From the results of the combined approaches, Organization is the most important dimension in SMS, which begins with Policies that convey to all staff the top managers’ vision on safety.

To Protect and Serve

To Protect and Serve

Improved nuclear power plant operations and safety through performance-based safety regulation

This paper illustrates some of the promise and needed future work for risk-informed, performance-based regulation (RIPBR). RIPBR is an evolving alternative to the current prescriptive method of nuclear safety regulation. Prescriptive regulation effectively constitutes a long, fragmented checklist of requirements that safety-related systems in a plant must satisfy. RIPBR, instead, concentrates upon satisfying negotiated performance goals and incentives for judging and rewarding licensee behavior to improve safety and reduce costs. In a project reported here, a case study was conducted concerning a pressurized water reactor (PWR) emergency diesel generator (EDG). Overall, this work has shown that the methods of RIPBR are feasible to use, and capable of justifying simultaneous safety and economic nuclear power improvements. However, it also reveals several areas where the framework of RIPBR should be strengthened. First, researchers need better data and understanding regarding individual component-failure modes that may cause components to fail. Not only are more data needed on failure rates, but more data and understanding are needed to enable analysts to evaluate whether these failures become more likely as the interval between tests is increased. This is because the current state of failure data is not sufficiently finely detailed to define the failure rates of individual component failure modes; such knowledge is needed when changing component-specific regulatory requirements. Second, the role of component testing, given that a component has failed, needs to be strengthened within the context of RIPBR. This includes formulating requirements for updating the prior probability distribution of a component failure rate and conducting additional or more frequent testing. Finally, as a means of compensating for unavoidable uncertainty as an obstacle to regulatory decision-making, limits to knowledge must be treated explicitly and formally. This treatment includes the formulation of probabilities through expert solicitation and the review of risk-informed, performance-based and engineering analyses used to evaluate proposed changes to existing technical specifications.

Occupancy classification for performance-based life safety

A fundamental concept of fire safety codes is the categorization of buildings according to their occupancy or use. The intrinsic purpose of such classification is to simplify the application of code regulations. While actual occupancy fire risk varies in every building space, administration is greatly facilitated by classification into a small number of categories. In application, once determined, occupancy class becomes the basis for building fire risk assessments. Traditional occupancy classification by building function is challenged by modern multifunctional structures that do not fit the earlier categories. Furthermore, these traditional categories ape unnecessary given the current capabilities of performance-based fire safety design and by performance-based fire safety codes.

Development of International Corporate Health and Safety Guidelines

Abstract The development and issuance of voluntary health and safety management guidelines by a parent corporation can encourage equivalent levels of protection at international operations by clearly communicating specific corporate expectations. Corporate guidelines provide a nonregulatory basis for consistent protection of employees across cultural and governmental borders and create a basis for measurement of performance-based health and safety goals for subsidiary organizations.

97/01964 Performance-based nuclear safety regulation

97/01964 Performance-based nuclear safety regulation

97/00427 Performance-based nuclear safety regulation

97/00427 Performance-based nuclear safety regulation