Structural Reliability Evaluation Research Articles

The JSME Standard on the reliability evaluation of mechanical structures and related trends

The JSME Standard on the reliability evaluation of mechanical structures and related trends

Evaluation of vehicular dynamic effects for the life cycle fatigue design of short‐span bridges

AbstractDedicated to Prof. Dr. Akimitsu Kurita on his 70th birthdayIn current bridge design codes or specifications, the dynamic effects of vehicles are considered by using a dynamic amplification factor (DAF) or dynamic load allowance (IM). However, a DAF is defined based on the ratio of the maximum dynamic load responses to the static load responses, and it is more appropriate for maximum value‐based strength design. For fatigue design, stress cycles other than the maximum stress ranges could contribute to fatigue damage accumulations. Meanwhile, on the capacity side, a reduction in fatigue strength due to structural deterioration, which is related to local environmental conditions, including temperature, humidity, etc., could introduce more uncertainties into structural safety and reliability evaluation. However, such multiple stress range effects and structural deterioration are not included in current bridge fatigue design. To evaluate the vehicular dynamic effects for the life cycle fatigue design of short‐span bridges, the present study proposes a new dynamic amplification factor for life cycle bridge fatigue design (DALC), which is defined as the ratio of the life cycle nominal live load stress range to the maximum static stress range. In contrast to other traditionally defined dynamic factors, the newly defined DALC includes information about both the structural loading and the structural capacity. Therefore, the multiple stress cycles from vehicle‐induced vibrations and the structural deteriorations from road surface conditions and corrosion of structural members are included. Parametric studies of DALC were carried out for multiple parameters and variables in the bridge's design life cycle, for instance, possible faulting days in each year, fatigue strength exponent, corrosion parameters and corrosion level. The stochastic properties and uncertainties from these variables are also considered in the DALC calculation.

Performance of Fibre Reinforced Concrete Structures - Modelling of Damage and Reliability

Steel fibre reinforced concrete (FRC) has higher ductility, it can save amount of convention reinforcement, labour and in consequence costs of the structure. However, broader use of SFRC as construction material is limited among others by lack of design codes. According to the previous study, reliability and safety of ordinary reinforced engineering can be verified using non-linear finite element analysis and several safety formats that are proposed in fib Model Code 2010. In the presented paper, safety formats are applied for fibre reinforced structures such as tunnel lining precast segment and individual approaches are compared. As tensile and shear cracks or compressive crushing can develop in the fibre reinforced concrete under severe conditions, the design combining numerical and experimental investigations together with safety formats is appropriate method how to obtain safe and reliable structure. Finite element method and advanced material models taking into account FRC properties such as shape of tensile softening branch, high toughness and ductility are described in the paper. Since the variability of FRC material properties is rather high, full probabilistic analysis seems to be the most appropriate format for evaluation of structural performance, reliability and safety.

Structural Stress Analysis and Reliability Evaluation for a New Speed Reducer

AbstractReducers are extensively used in many machines for reducing the speeds of mechanism. This paper proposed a new design of speed reducers to meet the performance requirements in high rigidness and large speed-reduction ratios. The movements of the reducer are designed based on the principles of differential displacements of the deceleration gear rings. The geometric models of the related components were designed using CAD software. The motions of mechanism were simulated for identifying the feasibility of designing including acquiring the kinematic properties. The mathematical models of structural stresses analysis were proposed so that the bending and contact stresses of the gear rings could be evaluated, accordingly. Finite element methods (FEM) were also used to analyze the structural stresses of the reducer. The studied results showed that the bending fracture of the gear rings would prior to its contacting fracture. The allowable loading of the reducer was then established according to the analyzed results of the maximum stresses on various transmitted torques. The methods of reliability evaluation were reported for considering the strength variation and calculating the reliabilities of the reducer at various loadings. The studied results are useful in structural design, stress analysis and reliability evaluation for developing high speed-reduction mechanisms.

Effect of ply level thickness uncertainty on reliability of laminated composite panels

The present study provides a comparative investigation and discussion on the influence of laminate thickness uncertainty on reliability of laminated composite. Laminate thickness uncertainty in three different scenarios is considered: component level thickness uncertainty, fiber-dominated ply level thickness uncertainty and matrix-dominated ply level thickness uncertainty. Monte-Carlo and Markov-chain Monte-Carlo methods are employed to calculate failure probabilities of symmetric and balanced laminate panels bearing uniaxial and multiaxial loads. It is shown that conventional considerations on laminate thickness uncertainty in the component level could underestimate or overestimate the composite failure probability. Ply level thickness uncertainty primarily caused by fiber or matrix quantity may also result in very different failure probabilities. This study highlights the importance of a thorough analysis and classification of the laminate thickness uncertainty in the ply level in order to achieve confident reliability evaluation of composite structures.

Reliability-Based Design Optimization of Trusses with Linked-Discrete Design Variables using the Improved Firefly Algorithm

In this paper, an approach for conducting a Reliability-Based Design Optimization (RBDO) of truss structures with linked-discrete design variables is proposed. The sections of the truss members are selected from the AISC standard tables and thus the design variables that represent the properties of each section are linked. Latin hypercube sampling is used in the evaluation of the structural reliability. The improved firefly algorithm is used for the optimization solution process. It was found that in order to use the improved firefly algorithm for efficiently solving problems of reliability-based design optimization with linked-discrete design variables; it needs to be modified as proposed in this paper to accelerate its convergence.

궤도차량 변속기 출력 하우징의 구조건전성 평가에 대한 연구

ABSTRACT Transmission of a tracked vehicle designed for multiple functions such as steering, gear-shifting, and braking is a core component of heavy vehicle to which the power is transferred based on combined technology of various gears, bearing, and fluid machineries. Robustness and durability of transmission, however, have been issued due to a large number of driving units and sub-components inside its body. Particularly, transmission housing is important structure which supports the transmission, and is made of aluminum alloy. Thus, structural robustness against such mechanical loading or vibration must be attained. Structural reliability evaluation through FEM analysis can save time and cost of the actual tests. In this study, structural evaluation is conducted on output housing of transmission, which is core component of tracked vehicle, using the simulation program. In addition, transmission dynamo test is performed to evaluate structural robustness of the output housing against the vibration which can be produced during the transmission operation.Key Words : Finite Element Analysis(유한요소해석), Transmission(변속기), Structure Analysis(구조해석), Modal Analysis (모달해석), Vibration Test(진동시험), Frequency Response (주파수 응답)

Stochastic analysis of laminated composite plate considering stochastic homogenization problem

This paper discusses a multiscale stochastic analysis of a laminated composite plate consisting of unidirectional fiber reinforced composite laminae. In particular, influence of a microscopic random variation of the elastic properties of component materials on mechanical properties of the laminated plate is investigated. Laminated composites are widely used in civil engineering, and therefore multiscale stochastic analysis of laminated composites should be performed for reliability evaluation of a composite civil structure. This study deals with the stochastic response of a laminated composite plate against the microscopic random variation in addition to a random variation of fiber orientation in each lamina, and stochastic properties of the mechanical responses of the laminated plate is investigated. Halpin-Tsai formula and the homogenization theory-based finite element analysis are employed for estimation of effective elastic properties of lamina, and the classical laminate theory is employed for analysis of a laminated plate. The Monte-Carlo simulation and the first-order second moment method with sensitivity analysis are employed for the stochastic analysis. From the numerical results, importance of the multiscale stochastic analysis for reliability evaluation of a laminated composite structure and applicability of the sensitivity-based approach are discussed.

Evaluation of structural reliability using simulation methods

Eurocode describes the 'index of reliability' as a measure of structural reliability, related to the 'probability of failure'. This paper is focused on the assessment of this index for a reinforced concrete bridge pier. It is rare to explicitly use reliability concepts for design of structures, but the problems of structural engineering are better known through them. Some of the main methods for the estimation of the probability of failure are the exact analytical integration, numerical integration, approximate analytical methods and simulation methods. Monte Carlo Simulation is used in this paper, because it offers a very good tool for the estimation of probability in multivariate functions. Complicated probability and statistics problems are solved through computer aided simulations of a large number of tests. The procedures of structural reliability assessment for the bridge pier and the comparison with the partial factor method of the Eurocodes have been demonstrated in this paper.

Reliability Evaluation of Distribution Structures Considering the Presence of False Trips

This paper presents a method for modeling the different modes of failures in a substation and feeder architecture along with updating the possible false tripping scenarios in it. A traditional approach to collectively assess the failure modes using reliability block diagram is reviewed, and the method is updated to count in the unaccounted false tripping scenarios. A generalizable radial feeder branching structure is adopted and the effect of total feeder length and number of feeders from each busbar is examined and modeled with the help of the updated reliability block diagram. The modeled trends are also studied from real-world substation architectures. Thus, the analysis attains an improved estimation of the complex hidden failure probabilities combining theoretical and practical models.

Short-circuit Failures Simulation for Evaluation of Structural Reliability of Power Supply Systems

The work is dedicated to the application of the sequential reduction method use to evaluate structural reliability of the industrial enterprises power supply systems. The review of publications has shown the lack of attention to these issues. Most researchers are focused on the reliability of electric power systems; probabilistic-statistical approach and the approach from the standpoint of financial and credit policy dominate here. The algorithm of scheme reduction is considered in terms of the most common type of failure - the short-circuit failure. The algorithm includes the following main steps –the identification of scheme elements, which allow selecting a group of elements, the failure of which leads to the failure of the entire group; the grouping of selected elements for which the equivalent reliability indices will be calculated; the convolving of resulting calculation scheme to the selected user and the definition of equivalent values the failure intensity, restoration time, and other reliability indices of interest. The algorithm is illustrated by an example of calculation scheme of the power supply system fragment containing a branch line. The calculations are carried out for the existing industrial enterprise.

Structural reliability evaluation of low-k nanoporous dielectric interlayers integrated into microelectronic devices

Structural reliability assessment on the integration of low-k nanoporous dielectrics into a multilayer structure, involving capping, chemical mechanical polishing, post-cleaning, and thermal annealing processes, was successfully demonstrated in a nondestructive manner.

SHM‐integrated bridge reliability estimation using multivariate stochastic processes

SummaryDetermination of response characteristics using probabilistic approaches is essential to deal with high level of load and resistance uncertainties in civil engineering structures. Multi‐span bridges present a significant problem regarding the varying nature of seismic loads on different bridge piers. With an emphasis on comparison of multi‐support excitation with the conventional uniform excitation, this paper aims at providing a framework to evaluate probabilistic seismic response and estimate reliability of bridges under multi‐support excitations simulated by multivariate stochastic processes. Moreover, the framework integrates the experimental data of a multi‐support seismic shaking table test of a multi‐span bridge structure as well as structural health monitoring (SHM) findings based on vibration measurements. The results demonstrate the importance of the multivariate stochastic processes, therefore, multi‐support excitation, on estimating seismic behavior of multi‐span bridges. Furthermore, this study proves the significance of structural parameter updating with respect to the evaluation of structural reliability. It is observed that the difference between the SHM‐integrated and the conventional reliability estimation results vary according to the change in bedrock conditions. Copyright © 2014 John Wiley & Sons, Ltd.

Application of Advanced Reliability Algorithms in Truss Structures

Many truss structures have been destroyed and collapsed one by one all over the world due to overloaded snow and wind load, etc. To investigate the mechanical property of truss structures, OpenSees package is utilized to evaluate reliability and sensitivity of three dimensional truss structures. Accuracy and efficiency of several reliability approaches, i.e., First Order and Second Moment, First Order Reliability Method, Second Order Reliability Method, Importance Sampling and Monte Carlo Method, are systematically compared and investigated. Young's modulus, yield strength, strain-hardening ratio, cross-sectional area of members, and concentrated loads and nodal coordinates in the x, y and z directions are treated as random variables. To diminish the computational effort and meanwhile guarantee the computational accuracy, random variables reduction technique (RVT) is employed in the reliability evaluation of truss structures.

Probabilistic Fatigue Life Prediction and Structural Reliability Evaluation of Turbine Rotors Integrating an Automated Ultrasonic Inspection System

The paper presents a general method and procedure for fatigue reliability assessment integrating automated ultrasonic non-destructive inspections. The basic structure of an automated ultrasonic inspection system is presented. Fatigue reliability assessment methodology is developed using uncertainty quantification models for detection, sizing, and fatigue model parameters. The probability of detection model is based on a classical log-linear model coupling the actual flaw size with the ultrasonic inspection reported size. Using probabilistic modeling, the distribution of the actual flaw size is derived. Reliability assessment procedure using ultrasonic inspection data is suggested. A steam turbine rotor example with realistic ultrasonic inspection data is presented to demonstrate the overall method. Calculations and interpretations of assessment results based on risk recommendations for industrial applications are given.

Reliability Analysis and Evaluation of Automobile Welding Structure

Metal welding structural strength was affected by the quality of automobile welding structure. Many accidents of the machines are caused by welding defects of automobile structure. Many welding parts are applied in the automobile. Reliability of automobile welding structure is studied and discussed in this paper. Failure modes and ultimate strength of automobile welding structure are obtained with bench test. The results show that all the failures happen in the welded region between clutch hub and clutch hub axle. Finite element model is built, and automobile welding structural strength is analyzed. And simulation results are in line with that of the experiment. Based on stress and strength interference model, automobile welding structure reliability is studied and discussed with theory of probability and reliability. In accordance with matching working load with structural strength, a new method of improvement design is proposed with the aim of automobile welding structural strength reliability. It provides a theoretical basis for automobile welding structure improvement design. And similar methods can be used to develop automobile welding structure and laser welding processes in future. Copyright © 2013 John Wiley & Sons, Ltd.

An efficient third-moment saddlepoint approximation for probabilistic uncertainty analysis and reliability evaluation of structures

This paper presents an efficient third-moment saddlepoint approximation approach for probabilistic uncertainty analysis and reliability evaluation of random structures. By constructing a concise cumulant generating function (CGF) for the state variable according to its first three statistical moments, approximate probability density function and cumulative distribution function of the state variable, which may possess any types of distribution, are obtained analytically by using saddlepoint approximation technique. A convenient generalized procedure for structural reliability analysis is then presented. In the procedure, the simplicity of general moment matching method and the accuracy of saddlepoint approximation technique are integrated effectively. The main difference of the presented method from existing moment methods is that the presented method may provide more detailed information about the distribution of the state variable. The main difference of the presented method from existing saddlepoint approximation techniques is that it does not strictly require the existence of the CGFs of input random variables. With the advantages, the presented method is more convenient and can be used for reliability evaluation of uncertain structures where the concrete probability distributions of input random variables are known or unknown. It is illustrated and examined by five representative examples that the presented method is effective and feasible.

The Research and Application of Masonry Structure Reliability Rating Method Based on Extenics

Aiming at masonry structure housing, establish the structure reliability evaluation index system. Subsidiary factors index dimensionless processing, the traditional matter-element model is analyzed, and based on this, the article puts forward an improved correlation functions, establish correlation function of the correlation factors of the index layer. Consider the weight coefficients of members,gave the extension index,combining analysis of the structural member reliability and extension comprehensive evaluation of the integral structural reliability, establish the masonry structure housing reliability assessment method framework. And prove the feasibility of this method through engineering examples.

An adaptive decoupling approach for reliability-based design optimization

Reliability-based design optimization (RBDO) is a powerful tool for design optimization when considering the probabilistic characteristics of the design variables. However, its use in practical applications is hindered by the huge computational cost during the evaluation of structure reliability. A number of algorithms have been proposed, such as reliability index approach (RIA), performance measure approach (PMA), decoupled approach and single-loop approach. In this paper, the adaptive decoupling approach (ADA) is developed. It adopts a new update angle strategy and a novel feasibility-checking method to improve the efficiency of probabilistic optimization. The update angle is utilized to reduce the number of performance function evaluations. And the probabilistic constraints are divided into feasible, active and violated categories, and only violated and active probabilistic constraints are evaluated precisely. The computation capability of ADA is demonstrated using five examples which are widely used to test RBDO methods. The comparison results show that ADA has the similar accuracy as existing methods, and it is also very efficient.

OS1413 き裂を有するシュラウドの合理的な健全性評価法の構築 : 2. 実験計画法とモンテカルロ法を組合せた統計的構造信頼性評価法の開発

OS1413 き裂を有するシュラウドの合理的な健全性評価法の構築 : 2. 実験計画法とモンテカルロ法を組合せた統計的構造信頼性評価法の開発