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The sight distance on horizontal curves could be restricted by a lateral obstruction such as a building or an upward side slope. In current design guides, the minimum horizontal sight offset (HSO) between such an obstruction and the centerline of the inner lane is determined using the analytic geometry of the sector to relate the curve radius to HSO, given a specific arc length (stopping sight distance). In this paper, limitations of the current design approach are highlighted. Furthermore, a new reliability-based methodology was developed to calculate HSO on 3D alignments considering the variations of several design parameters. Two design aids were further prepared as an example to show the applicability of the developed approach. The first one is valid for design purposes using 400 m horizontal curve combined with vertical curves of different curvature values whereas the second is valid for hazard assessment of existing designs using 400 m radius and 2H:1V side slope. Key words: lateral clearance, highway design, reliability analysis, safety, 3D alignment. La distance de visibilite dans les courbes horizontales pourrait etre restreinte par une obstruction laterale telle qu'un batiment ou une pente laterale positive. Les guides de conception actuels determinent le decalage horizontal minimum de visibilite (HSO) entre une telle obstruction et la ligne mediane de la voie interieure en utilisant la geometrie analytique du secteur afin d'associer le rayon de la courbe au HSO pour une longueur d'arc donnee (distance de visibilite d'arret). Cet article souligne les limites de l'approche courante de conception. De plus, une nouvelle methode, basee sur la fiabilite, a ete developpee pour calculer le HSO sur des alignements tridimensionnels en tenant compte des variations de plusieurs parametres de conception. Deux exemples de conception ont ete realises pour montrer l'applicabilite de l'approche developpee. Le premier est valide aux fins de conception; il utilise une courbe horizontale de 400 m combinee a des courbes verticales de differentes courbures, alors que le second est valide pour l'evaluation des risques des conceptions existantes; il utilise un rayon de 400 m et une pente laterale positive de 2H:1V. Mots-cles: degagement lateral, conception des autoroutes, analyse de fiabilite, securite, alignement tridimensionnel. [Traduit par la Redaction], 1. Introduction There are two approaches one can follow in the design process, namely deterministic and probabilistic. The deterministic approach is widely used in current highway design guides for its [...]

As any model is only an abstraction of the real world, model uncertainty always exists. The magnitude of model uncertainty is important for geotechnical decision making. If model uncertainty is not considered, the geotechnical predictions and hence the decisions based on the geotechnical predictions might be biased. In this study, a framework for characterizing geotechnical model uncertainty using observation data is proposed. The framework is based on the concept of multivariable Bayesian updating, in which the statistics of model uncertainty are updated using observed performance data. Uncertainties in both input parameters and observed data can be considered in the proposed framework. To bypass complex computational works involved in the proposed framework, a practical approximate solution is presented. The proposed framework is illustrated by characterizing the model uncertainty of four limit equilibrium methods for slope stability analysis using quality centrifuge test data. Parametric study in the illustrative example shows that both quality and quantity of the performance data could affect the determination of the model uncertainty, and that such effects can be systematically quantified with the proposed method. DOI: 10.1061/(ASCE)GT.1943-5606.0000018 CE Database subject headings: Bayesian analysis; Uncertainty principles; Slope stability; Centrifuge model; Reliability.

An alternative approach of analyzing laterally loaded piles in the ubiquitous spreadsheet platform is presented. The numerical procedure couples nonlinear pile flexural rigidity ([E.sub.p][I.sub.p]) with nonlinear p-y analysis. The deterministic study is then extended to carry out reliability analysis, which reflects the uncertainties and correlation structure of the underlying parameters. The reliability index is evaluated based on the alternative intuitive perspective of an expanding equivalent ellipsoid in the original space of the random variables. This paper investigates two modes of failure: deflection and bending moment, and considers non-normal random variables. Spatial variability of the soil medium is accounted for by incorporating an autocorrelation model. The spreadsheet-based reliability approach can also be coupled with stand-alone programs via the response surface method. The probabilities of failure inferred from reliability indices agree well with Monte Carlo simulations. Simple reliability-based design is demonstrated, in which the appropriate pile section or length that satisfies target reliability in one or more limit states is sought. CE Database subject headings: Correlation; Design; Failure modes; Limit states; Monte Carlo method; Nonlinear analysis; Optimization; Pile lateral loads; Reliability; Soil properties.

In this paper, the excavation-induced settlement determined by the KJHH model, a recently developed semiempirical model, is used to assess the serviceability reliability of adjacent buildings. The calculated settlement, considered as the load in the context of reliability analyses in this paper, is compared with a tolerable settlement, considered as the resistance herein. The reliability of the adjacent building against 'damage' (defined herein as the violation of serviceability requirements such as having intolerable settlement) is first analyzed and the probability of exceedance (i.e., exceeding the tolerable settlement) is calculated. Furthermore, as the excavation proceeds, observed settlement at the current excavation stage is used to update the prediction of settlement at subsequent stages, and the probability of exceedance is updated accordingly. CE Database subject headings: Reliability; Probability; Bayesian analysis; Excavation; Settlement; Serviceability; Damage.

The majority of single-family dwellings in the United States are light-frame wood construction. Residential construction practices have evolved gradually over the years, most light-frame wood structures have not been structurally engineered, and many residential buildings suffered significant damage in recent hurricane and earthquake disasters. As a result, new concepts and methodologies are evolving to better predict and evaluate the performance of wood frame structures exposed to natural hazards and to support improved residential building practices. This paper examines the behavior of typical light-frame wood structural systems in the central and eastern United States under earthquake hazards. Nonlinear structural analysis tools and stochastic methods are used to model the uncertainties in ground motion intensity and structural response. Fragility curves defining damage state probabilities as a function of ground motion intensity are developed for typical lateral force-resisting shear wall systems subjected to increasing levels of ground motion. A comparison of these fragilities with those embedded in HAZUS provides additional perspective on damage potential for residential construction in regions of low-to-moderate seismicity. DOI: 10.1061/(ASCE)0733-9445(2008)134:8(1353) CE Database subject headings: Standards and codes; Deformation; Earthquakes; Reliability; Shear walls; Structural engineering; Wood structures.

Reliability of power-electronic modules is of paramount importance for the commercial success of various types of electric vehicles. In this paper, we study the technical feasibility of detecting and utilizing early symptoms and warning signs of power-module degradation due to thermomechanical stress and fatigue and develop a prognostic system that can monitor the state of health of the power modules in electric, hybrid, and fuel-cell vehicles. A special degradation trace on the [V.sub.CEsat] of the insulated-gate bipolar-transistor modules was observed by a power-cycling accelerated test, which was not reported in literatures. A prognostic system based on utilizing the aforementioned trace is then developed. The system consists of the hardware architecture and current adaptive-algorithm-based software architecture. In addition, this prognostic system hardly increases the hardware cost on existing vehicle-driver system. An extensive simulation based on MATLAB/Simulink verifies the developed prognostic system. Index Terms--Electric vehicles, electronics module, hybrid vehicles, reliability.

This paper presents the application of compact insulated gate bipolar transistor and p-i-n diode models, including features such as local lifetime control and field-stop technology, to the full electrothermal system simulation of a hybrid electric vehicle converter using a lookup table of device losses. The vehicle converter is simulated with an urban driving cycle (the Federal Urban Driving Schedule), which is used to generate transient device temperature profiles. A methodology is also described to explore the converter reliability using the temperature profile, with rainflow cycle counting techniques from material fatigue analysis. The effects of ambient temperature, driving style, and converter design on converter reliability are also investigated. Index Terms--Compact modeling, electrothermal simulation, mission profile, power semiconductor devices, rainflow cycle counting, reliability, thermal cycling.

We propose a decision-based approach for reliability design when there is insufficient information for constructing probabilistic models. The approach enables a designer to perform reliability-cost trade-offs and to assess the importance of variability and epistemic uncertainty. A method for decision under epistemic uncertainty is first presented and justified by presenting axioms on a decision maker's (DM's) preferences and by assuming that the DM's goal is to find the most immune act (in terms of having undesirable consequences) to deviations of the state of the world from an expected state. Thus, the philosophy of the method is similar to that of robust reliability (Ben Haim, Y., 1996, Robust Reliability in the Mechanical Sciences, Springer-Verlag, Berlin). A new formulation of reliability design problems is proposed based on the above decision method and is compared to two reliability-based design optimization formulations that minimize cost given a maximum acceptable failure probability or maximize expected utility. The method is demonstrated on a decision where a designer has to choose between two materials for a structure. [DOI: 10.1115/1.2712213]

The computational efficiency of the reliability-based design optimization(RBDO) can be a critical issue when high-fidelity simulation methods are used. An efficient RBDO framework is presented that utilizes a single-loop RBDO algorithm in which reliability analysis and optimization are conducted in a sequential manner by approximating the limit-state function. A further improvement in computational efficiency is achieved by applying the fixed sensitivity of the limit-state function to the reliability analysis and the equivalent deterministic constraint calculation. To guarantee the convergence of the single loop and the fixed sensitivity algorithm, a trust region-sequential quadratic programming RBDO strategy, is developed. The proposed framework validates low-fidelity approximation models in the trust region radius. The framework is examined by solving an analytical test problem to show that the proposed strategy has the computational efficiency over existing methods while maintaining accuracy. The proposed strategy is applied to a three-dimensional aerodynamic wing design problem to get improved results satisfyiug probabilistic constraints.

The multi-version programming technique is a method to increase the reliability of safety critical software. In this technique a number of versions are developed and a voting scheme is used before a final result is provided. In the analysis of this type of systems, a common assumption is the independence of the different versions. However, the different versions are usually interdependent and failures are correlated due to the nature of the product design and development. One version may fail simultaneously with another version because of a common cause. In this paper, a model for these dependent failures is developed and studied. Using the developed model, a reliability function can be easily computed. A method is also proposed to estimate the parameters of the model. Finally, as an application of the developed model, an optimal testing resource allocation problem is formulated and a genetic algorithm is presented to solve the problem., Nomenclature [c.sub.i] = expected cost per unit of testing time on the ith version; d = expected risk cost if the system fails in operation; Z([i.sub.1], [i.sub.2],..., [i.sub.j]) = the [...]

A stepwise response surface approach is proposed in this paper. The response surface is determined by modified stepwise regression, so that the square and cross terms can be absorbed into the model automatically according to their actual contribution, which is calculated by repeated variance analysis. Besides, by applying a weighting factor to the statistical value of contribution and changing the thresholds of introduction and rejection, the entry of each term can be controlled in a fairly flexible manner. None other criteria than those in the traditional statistics are needed to check the goodness of fit. Considering the relatively small sample set at the beginning, the algorithm starts with a linear response surface. As the adaptive iteration proceeds, the bar to quadratic terms is lifted gradually to allow ordered entry. Since the sampling points in one step of iteration are recycled in the succeeding ones, a simple experimental design is enough to fit a robust response surface. A double bottom hull system is analyzed with randomized Young's modulus, load distribution, and geometric properties. The sensitivity analysis is also performed with respect to the random variables and the parameters in their distributions. [DOI: 10.1115/1.1493199] Keywords: Structural Reliability, Response Surface Method, Stepwise Regression, Double Hull Structure

In this paper, we will identify many of the application and maintenance questions that may have an impact on perceived versus actual reliability, such as the following. 1) Does the application of a single multifunction system for primary and backup protection of a given zone create potential reliability problems? What engineering, operating, and economic factors must be considered? 2) Should the same manufacturer or different manufacturers be used when independent multifunction systems are applied for primary and backup protection? What engineering, operating, training, and economic factors must be considered? 3) Is the overall reliability of numeric protection systems more likely to be influenced by hardware or software related issues? What factors should be considered before upgrading existing hardware and software? 4) What type of maintenance is actually being performed on multifunction systems? What factors should be considered before changing established maintenance guidelines? The challenge of today's protection engineer is to make sure that protection reliability is maintained at or above the technologies being replaced. Understanding the application issues and potential problem areas is critical to that success. This paper will provide insight and guidance toward that end. Index Terms--Commissioning, multifunction protection, numerical, operations analysis, predecessor technology, product evaluation, protection philosophy, reliability.

Simple reliability analyses, involving neither complex theory nor unfamiliar terms, can be used in routine geotechnical engineering practice. These simple reliability analyses require little effort beyond that involved in conventional geotechnical analyses. They provide a means of evaluating the combined effects of uncertainties in the parameters involved in the calculations, and they offer a useful supplement to conventional analyses. The additional parameters needed for the reliability analyses - standard deviations of the parameters - can be evaluated using the same amount of data and types of correlations that are widely used in geotechnical engineering practice. Example applications to stability and settlement problems illustrate the simplicity and practical usefulness of the method.

It is shown that if a formula is constructed from noisy 2-input NAND gates, with each gate failing independently with probability [Epsilon], then reliable computation can or cannot take place according as [Epsilon] is less than or greater than [e.sub.0] = (3 - [-square root of 7])/4 = 0.08856 .... Index Terms - Logical formulas, NAND gates, reliability.

Today's projects suffer from high uncertainty, great demand for accelerated speed, and severe scarcity of attention of the project manager. At the same time, the schedules of today's projects are expected to be more reliable than ever. This paper presents a new concept for improving the reliability of a project schedule suffering from uncertainty in the duration of its activities. The paper shows that the technique for applying the new concept requires minimal information, incorporates subjective information, is simple to use, and assists in the preparation of project schedules at a desirable level of reliability. Specific examples demonstrate the use of the technique for: (1) calculating the reliability of the project schedule; (2) enhancing the reliability of the project schedule; (3) reducing project duration without diminishing its reliability; and (4) examining how overlapping of project activities affects its reliability.

Assembly level reliability (ALR) is a 4-step method which combines various techniques to produce synergistic effects for integrated circuit manufacture. Development of test chip, characterization and authenticity of the chip functionality, decrease in qualification costs with test chips and using effective reliabilty measuring systems are necessary for the progress of ALR. Such rapid testing with knowledge of failure mechanisms provides faster product qualification for a time-to-market advantage.

Byline: Bharatendra K. Rai Yearly warranty cost of major automobile companies runs into billions of dollars. In addition, market- driven need for wider warranty coverage exposes these companies to the risk of higher warranty spending. Warranty cost reduction programmes have thus become a major objective and challenge in these companies. Towards this, warranty data that capture vehicle failures in field conditions contain rich source of information for useful feedback to designers and engineers working on current and forward model vehicles for reliability and robustness improvements. However, obtaining accurate feedback using warranty data becomes challenging due to issues involving data quality. This paper presents strategies for automobile warranty data analysis that helps obtain meaningful feedback towards reliability and robustness improvements leading to warranty cost reduction. Role of hazard plots in giving clues about nature of noise factors that influence failure is presented. Strategies for stratification of warranty data in terms of customer-reported concerns and/or parts reported to be the cause of failure to prioritise reliability and robustness improvement projects are discussed. Uses of geographic plots in gaining insight about seasonality and location effect are also provided.

Byline: Warren Jocz, Chongwen Zhou This paper presents three fatigue strength reliability demonstration case studies, one each at the component, subsystem and system levels. These case studies utilise classical (traditional), yet often underutilised, methods for fatigue strength assessments. It is the opinion of the authors that a primary reason behind the underutilisation of these methods lies in the operational definition of reliability under which many engineering organisations (especially automotive OEMs and their suppliers) currently make fatigue performance assessments. This paper supports an alternative definition of reliability, which when adopted into practice has reinvigorated the use of traditional (classical) fatigue performance demonstration techniques – techniques which, in recent years, were frequently replaced by key-life and/or real-world user testing. These case studies highlight the engineering information, cost and timing advantages associated with the application of these traditional fatigue performance techniques.

Byline: Sankaran Mahadevan, Ruoxue Zhang This paper develops a methodology for reliability test planning using computational reliability methods. Empirical methods of reliability estimation are based on tests on actual components and the use of classical statistics. Computational methods of reliability analysis propagate the uncertainty information about primitive variables through the system computational model to estimate the reliability. This paper combines the two approaches for cost-effective reliability testing. The proposed method also includes the uncertainties due to limitations and bias in data and the computational model. An adaptive method is developed to determine the number of tests needed to achieve a desired confidence level in the reliability estimate, by combining computational prediction and test data. The proposed approach is applied to the probabilistic life prediction of a composite helicopter rotor hub under fatigue loading, based on the delamination failure analysis of composite laminates.

This letter describes an approach using Benders decomposition to decompose security-constrained optimal power flow (DSCOPF). It provides a complexity analysis to give insight into the improved computing speeds obtained using the approach. The method is illustrated on two six-bus test systems and on the IEEE reliability test system. Index Terms--Benders decomposition, parallel computing, security-constrained optimal power flow.

The possibility of artifactual reliability of multiple scales embedded in a single forced-choice instrument was examined. It was demonstrated that, by introducing one perfectly reliable scale in an instrument when responses to all of the remaining scales were random, considerable internal consistency reliability was generated in the remaining scales. The findings cast doubt on the advisability of the practice of making construct-oriented interpretation of ipsative scores from multiple-scale instruments. Alternative procedures for obtaining the reliability estimates necessary for demonstration of construct validity of the scales are recommended. (Reprinted by permission of the publisher.)