•Vibration of train-bridge couple system with random parameters is calculate.•The efficiency and accuracy of NPEM in train-bridge couple vibration is evaluated.•Response with random parameter and ...different coefficient of variation is discussed.
In the analysis of train-bridge coupled vibration system, randomness of parameters of high-speed railway bridge cannot be ignored. The new point estimate method (NPEM) is a kind of accurate and efficient method to calculate the random response and reliability. In this paper, NPEM is applied to analyze the random dynamic responses of 3D train-bridge coupled system with random parameters, including parameters of bridge materials, environment factor and prestressing parameters. Newmark-β approach is applied as the integration algorithm, and the Monte Carlo method is used to validate the feasibility of the NPEM. The results show that NPEM can be combined with random system accurately and efficiently. Furthermore, the influences of different random parameters distributions are discussed.
•Method for systematically developing reactor operators’ knowledge base is proposed.•Developed knowledge base supports cognitive modeling of human performance.•The knowledge base related to severe ...accidents in nuclear power plants is developed.•Advantages of the proposed method for knowledge base development are discussed.
Methods based on cognitive modeling have attracted increasing attention in the human reliability analysis community. In such methods, the operator knowledge base plays a central role. This paper proposes a method for systematically developing the knowledge base of nuclear power plant operators. The method starts with a systematic literature review of a predefined topic. Then, the many collected publications are reduced to summaries. Relevant knowledge is then extracted from the summaries using an improved qualitative content analysis method to generate a large number of pieces of knowledge. Lastly, the pieces of knowledge are integrated in a systematic way to generate a knowledge graph consisting of nodes and links. As a case study, the proposed method is applied to develop the knowledge base of reactor operators pertaining to severe accidents in nuclear power plants. The results show that the proposed method exhibits advantages over conventional methods, including reduced reliance on expert knowledge and improved traceability of the process. Generalization of the proposed method to other sources of materials and application of the knowledge base are also discussed. Although this paper is focused on nuclear applications, the proposed method may be extended to other industrial sectors with little additional effort.
Due to its advantages of simplicity and high efficiency, Hasofer–Lind and Rackwitz–Fiessler (HL–RF) method is widely used in structural reliability analysis. However, it may encounter difficulties in ...convergence, such as periodic oscillation, bifurcation and chaos when complex performance functions are involved. In this study, a new efficient and robust method is proposed to deal with the convergence problem and is applied to reliability-based design optimization (RBDO). The strategy is to modify the search direction of HL–RF to make it adaptable to changes, thereby reducing the risk of periodic oscillations. A step size adjustment formula is then established to adaptively adjust the finite-step size to prevent bifurcation or chaos. In addition, the proposed method is integrated into double loop method (DLM) to strengthen the robustness and efficiency of DLM for complex RBDO problems. The efficiency and robustness of the proposed method are demonstrated by comparison with other existing first order reliability methods (FORMs) through five numerical examples and two structural examples. Two complex RBDO problems also show that DLM based on the proposed method has the ability to solve complex RBDO problems.
•A new efficient and robust structural reliability method is proposed.•The search direction of HL–RF method is modified.•A new adaptive step size adjustment formula is established.•The proposed method improves the efficiency and robustness of FORM method.•The proposed method is applied to solve complex RBDO problems.
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This paper discusses piezoelectric acoustic devices based on widely used piezoelectric materials. Commonly used piezoelectric thin film deposition techniques and the influence of ...process parameters on the growth, texture and orientation of the films are discussed. Etching techniques are also outlined. A comparative study of different devices developed previously is given. Also, applications of developed devices in aero-acoustic and medical fields have been briefly discussed. Flow charts of various techniques of deposition along with a combined one for full acoustic device fabrication are given. Various techniques, frequently used for thin film characterization have been discussed. The testing and measurement techniques to determine the responses of acoustic devices such as sensitivity, resonance frequency, frequency response, piezoelectric co-efficient etc. have been briefly illustrated. This paper discusses common failure modes with respect to the field of use of acoustic devices. It also concisely discusses various reliability tests done in industries to assess the quality of the developed devices. This review has also suggested directions for future development of thin film acoustic sensors.
•The three papers document two large-scale human reliability analysis (HRA) empirical studies.•The two studies compared HRA method predictions against operator performance on nuclear power plant ...(NPP) simulators.•The studies examined the strengths and weaknesses of HRA methods and the factors contributing to variability in HRA results.•Study achievements, lessons learned, recommendations and insights for improving HRA are presented in the papers.
This is the last in a series of three papers documenting two large-scale human reliability analysis (HRA) empirical studies – the International HRA Empirical Study and the US HRA Empirical Study. The goal of the two studies was to develop an empirically-based understanding of the performance, strengths, and weaknesses of HRA methods by comparing HRA method predictions against actual operator performance in simulated accident scenarios on nuclear power plant (NPP) simulators. This paper first addresses areas where there is convergence between the two studies and where differences lie. Then it summarizes the combined insights and conclusions, including key findings on HRA in general through lessons learned about the HRA methods assessed in the studies and specific recommendations for improving guidance, practice and methods. Then it discusses the relevance and usefulness of simulator data for HRA in general. Finally, it presents the key achievements and overall conclusions of the two studies taken together.
•Demand-based warm standby systems with capacity storage are modeled.•Different utilization sequences of warm standby and stored capacity are considered.•Multi-valued decision diagram is proposed for ...system reliability evaluation.•Chronological characteristics of warm standby activation are embedded.•The method allows systems with arbitrary time-to-failure distributions.
Warm standby is an energy-saving redundancy technique that consumes less energy than a conventional hot standby method. It can be naturally integrated with an energy storage technique to enhance system reliability. However, the integration approach of both techniques and the advantage it affords to system reliability have not been reported in literature. This study resolves this limitation by formulating a novel reliability model for demand-based warm standby systems with capacity storage. In this model, the chronological characteristics of warm standby components are explicitly explored before and after their activation. Moreover, different utilization sequences of warm standby components and storage components are embedded to analyze the effects of these sequences on system reliability. A multi-valued decision diagram is developed to evaluate system reliability considering successful activation probabilities of warm standby components. This diagram is applicable to arbitrary component lifetime distributions and warm standby systems. Numerical examples are presented to verify the application of the proposed methodology.
•A probability-interval hybrid reliability method is proposed for cracked structures.•Intervals are used to deal with the parameters with epistemic uncertainty.•The SBFEM is adopted to calculate the ...stress intensity factors.•An efficient algorithm is formulated to compute the fracture reliability interval.
The uncertainty modeling and reliability analysis for cracked structures in which there are many inherently uncertain parameters is very important in engineering. This paper presents a probability-interval hybrid uncertainty model and a corresponding efficient reliability analysis method for the structural cracking problem. Through introducing interval uncertainty, the method can effectively address the difficulties in the epistemic uncertainty modeling due to the lack of experimental samples, which expand greatly the applicability of reliability analysis technology in cracked structure research. The parameters are classified, and subsequently the probability and interval methods are separately applied to address the parameters with sufficient and insufficient experimental samples. A probability-interval hybrid reliability analysis model for the cracked structure based on the traditional first-order reliability method is developed. The scaled boundary finite element method is adopted to calculate the stress intensity factors from which the performance function can be obtained. Based on these calculations, an efficient iterative algorithm using the response surface is developed to solve the hybrid reliability model and calculate the interval of the failure probability of the cracked structure. Four numerical examples are presented for verification of the validity of the proposed method.
The single-loop approach (SLA) for reliability-based design optimization (RBDO) is one of the most efficient schemes for optimization problems with linear and weak nonlinear probabilistic ...constraints. However, it may produce unstable results or increase computational efforts when using the ordinary search direction to determine the optimum design in RBDO problems with highly nonlinear probabilistic constraints. The conjugate gradient (CG) is a promising sensitivity vector for locating the most probable point (MPP) of highly nonlinear concave performance functions. However, the MPP computation using the CG may require a high computational burden for convex constraints To overcome the drawbacks of the SLA the adaptive conjugate single-loop approach (AC-SLA) is proposed for RBDO problems with a large variety of nonlinear constraints. The sensitivity vector of the probabilistic constraints is adaptively computed using the CG vector with a dynamical conjugate scalar factor (DCF). The DCF is adjusted within the range from 0 to 2 using two adaptive coefficients, which are adapted based on the new and previous points. Moreover, the Lyapunov exponents are developed as a general tool for detecting the robustness of different MPP approximation algorithms. The method is also applied to solve a reliability-based topology optimization (RBTO) problem. The ability of the AC-SLA in six RBDO benchmark problems, one applicable to an RBDO aircraft engineering problem and one for RBTO problem, is compared in terms of both robustness and efficiency using the SLA, performance measure approach (PMA), reliability index approach (RIA), and sequential optimization and reliability assessment (SORA). The numerical experiments demonstrate that the convergence capability of the proposed AC-SLA is significantly superior to the PMA, RIA, and SORA. The computational effort of the AC-SLA is significantly reduced, with stable results.
•The SLA is improved using the adaptive conjugate search direction in RBDO and RBTO.•The conjugate sensitivity vector is used to compute the for large variety of nonlinear probabilistic constraints.•The dynamical conjugate scalar factor is computed using mean design and next points in the range from 0 to 2.•Performances of AC-SLA are compared with RBDO methods using benchmark and applicable problems.•Efficiency and robustness of AC-SLA are vitally superior compared to other RBDO methods.
•Imprecise probabilities allow for explicitly taking epistemic uncertainty into account.•P-boxes are of interest for engineering analysis due to their mathematical straightforward description.•An ...overview of methods for construction of p-boxes based on available information is given.•The state-of-the-art in propagation schemes for p-boxes is discussed.
The consideration of imprecise probability in engineering analysis to account for missing, vague or incomplete data in the description of model uncertainties is a fast-growing field of research. Probability-boxes (p-boxes) are of particular interest in an engineering context, since they offer a mathematically straightforward description of imprecise probabilities, as well as allow for an intuitive visualisation. In essence, p-boxes are defined via lower and upper bounds on the cumulative distribution function of a random variable whose exact probability distribution is unknown. However, the propagation of p-boxes on model inputs towards bounds on probabilistic measures describing the uncertainty on the model responses is numerically still very demanding, and hence is subject of intensive research. In order to provide an overview on the available methods, this paper gives a state-of-the art review for the modelling and propagation of p-boxes with a special focus on structural reliability analysis.
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