Practical Reliability-based Design Research Articles

A Transformation-Based Improved Kriging Method for the Black Box Problem in Reliability-Based Design Optimization

In order to overcome the drawbacks of expensive function evaluation in the practical reliability-based design optimization (RBDO) problem, researchers have proposed the black box-based RBDO method. The algorithm flow of the commonly employed RBDO method for the black box problem consists of the outer construction loop of the surrogate model of the constraint function and the inner surrogate model-based solving loop. To improve the solving ability of the black box RBDO problem, this paper proposes a transformation-based improved kriging method to increase the effectiveness of the two loops identified above. For the outer loop, a sample distribution-based learning function is suggested to improve the construction efficiency of the surrogate model of the constraint function. For the inner loop, a paired incremental sample-based limit reliability boundary construction approach is suggested to transform the RBDO problem into an equivalent deterministic design optimization problem that can be efficiently solved by classical optimization algorithms. The test results of five cases demonstrate that the proposed method can accurately construct the surrogate model of the constraint function and efficiently solve the black box RBDO problem.

Reliability-based design applied to retaining walls

Geotechnical engineers have long used the lumped factor of safety approach in the design of foundations and retaining walls. A more recent alternative is the limit state approach using partial factors, for example as suggested in Eurocode 7. Yet another approach is perhaps more flexible and rational: design based on a target reliability index that reflects the uncertainty of the parameters and their correlation structure. Among the various versions of reliability indices, the Hasofer–Lind index and first-order reliability method (FORM) are more consistent. This paper illustrates practical reliability-based design procedures for retaining walls based on the Hasofer–Lind index and FORM. Correlated normal and non-normal random variables are considered. The efficient spreadsheet-based probabilistic approach, based on the work of Low & Tang, achieves the same result as the Hasofer–Lind method and FORM, but uses an intuitive expanding dispersion ellipsoid perspective that greatly simplifies the computations and interpretations. The differences between a reliability-based design and one based on partial factors will be discussed. Sensitivity information as conveyed in a reliability analysis will be studied. The probabilities of failure inferred from reliability indices will be compared with Monte Carlo simulations. This paper deals only with certain aspects of reliability, namely methodology and concepts, and not reliability in its widest sense.

Reliability-based design applied to retaining walls

Geotechnical engineers have long used the lumped factor of safety approach in the design of foundations and retaining walls. A more recent alternative is the limit state approach using partial factors, for example as suggested in Eurocode 7. Yet another approach is perhaps more flexible and rational: design based on a target reliability index that reflects the uncertainty of the parameters and their correlation structure. Among the various versions of reliability indices, the Hasofer–Lind index and first-order reliability method (FORM) are more consistent. This paper illustrates practical reliability-based design procedures for retaining walls based on the Hasofer–Lind index and FORM. Correlated normal and non-normal random variables are considered. The efficient spreadsheet-based probabilistic approach, based on the work of Low & Tang, achieves the same result as the Hasofer–Lind method and FORM, but uses an intuitive expanding dispersion ellipsoid perspective that greatly simplifies the computations and interpretations. The differences between a reliability-based design and one based on partial factors will be discussed. Sensitivity information as conveyed in a reliability analysis will be studied. The probabilities of failure inferred from reliability indices will be compared with Monte Carlo simulations. This paper deals only with certain aspects of reliability, namely methodology and concepts, and not reliability in its widest sense.

Practical reliability-based design of gear pairs

Techniques from perturbation method and reliability-based design theory are employed to present the practical and effective method for the reliability-based design of gear pairs. The theoretical formulae of reliability-based design of gear pairs are obtained. The corresponding program can be used to obtain the reliability-based design parameters of gear pairs accurately and quickly.

Reliability-based design for transmission line structure foundations

Abstract This paper presents one of the geotechnical initiatives in reliability-based code development that has been sponsored by the Electric Power Research Institute for transmission line structure foundations. The framework for the development of a practical reliability-based design approach is illustrated using the design of drilled shafts (bored piles) for uplift under undrained loading. A target reliability index of 3.2 is selected based on the reliability indices implied by existing working stress designs. Two simple design formats (load and resistance factor design and multiple resistance factor design) are rigorously calibrated using the first-order reliability method to produce designs that achieve a known level of reliability consistently.

Practical Reliability-Based Design Approach for Foundation Engineering

A research study was completed recently that was directed toward the development of practical, reliability-based design (RBD) equations specifically for foundation engineering. Some of the key RBD principles used in the study are presented. The important considerations involved in the development of practical and robust RBD criteria are emphasized. In particular, the selection of an appropriate reliability assessment technique and the careful characterization and compilation of geotechnical variabilities are important because of their central role in the calculation of the probability of failure and the assessment of the target reliability level. An overview of a simplified RBD approach is given, and an application of this approach to the ultimate limit state design of drilled shafts under undrained uplift loading is discussed.

Practical Reliability-Based Design Approach for Foundation Engineering

A research study was completed recently that was directed toward the development of practical, reliability-based design (RBD) equations specifically for foundation engineering. Some of the key RBD principles used in the study are presented. The important considerations involved in the development of practical and robust RBD criteria are emphasized. In particular, the selection of an appropriate reliability assessment technique and the careful characterization and compilation of geotechnical variabilities are important because of their central role in the calculation of the probability of failure and the assessment of the target reliability level. An overview of a simplified RBD approach is given, and an application of this approach to the ultimate limit state design of drilled shafts under undrained uplift loading is discussed.

疲労き裂進展過程における不確定要因の相乗効果

There exist many well-known uncertainty factors associated with the fatigue crack propagation process, among which two major uncertainty factors, one due to material inhomogeneity and the other due to the randomness of applied loads, undoutedly play an inevitably important role. Uncertainties caused by these two factors must be clarified not only individually but also jointly, since the cross-effect of both factors may arise under random loading and this is often the case in engineering reality.In this respect, the present paper deals with the case where crack propagation resistance and stress amplitude of applied load are both stochastic processes and, in addition, each correlation decays exponentially with the increase of time difference. Towards this case has first been constructed a theoretical stochastic model with the aid of a Markov approximation method. Then the aforementioned cross-effect has been evaluated and discussed in detail, and the distribution characteristics of the model have been investigated by utilizing numerical computation techniques. Finally, the wide applicability of the proposed model has been emphasized by exemplifying a useful application of this model towards the inspection period determination problem which is often encountered in the practical reliability-based design of machines and/or structures.