Papers by Keyword: Structural Reliability

Abstract: The Churches of the Broumov region are well known for their unique baroque architecture, distinct shapes, sizes, and constitutes an integral part of the Czech cultural heritage. The St. Barbara’s Church that has been studied in this article, is in the Otovice village of Broumov. It was built in the year 1726 by Bavarian architects Christoph Dientzenhofer and Kilian Ignaz and is significant because of its religious, artistic and historic values. The main objective of this study is to evaluate the structural safety and stability of St. Barbara’s Church based on a probabilistic approach. A deterministic assessment of the structure is carried out and the results are assessed concerning the present site condition. Depending upon the observed damages, a condition for failure is defined for the structure. The uncertainties in the material parameters are considered and reliability analysis is performed to determine the reliability index, probability of failure and influence of different material parameters in the structural stability.

Abstract: Evaluating the integrity of a structure consists in proving its ability to realize its mechanical functions for all modes of loading, normal or accidental, and throughout its lifetime. In the context of nuclear safety, the most important structures consider the presence of a degradation grouping several aspects, such as cracks. In this context, the fracture mechanics provide the tools needed to analyze cracked components. Its purpose is to establish break criteria for judging loading margins in normal or accidental operating conditions. The seismic load is one of the dominant loads for the failure assessment of the pipes. Its probabilistic dispersion, however, was not taken into account in the past probabilistic fracture mechanics analysis. The objective of this paper is to simulate and analyze the effect of abnormal stress on the reliability of tow pipe sizes. As result the seismic stress has more effect on the break probability, but not for the leak probability. In the case without a seismic load, the break probability is mainly dominated by an initial crack size. The earthquake has much effect on the break probability for the large diameter pipe, not for the small diameter pipe. In the large diameter pipe, the break probability increases gradually with the time. The leak probability of both pipe sizes is not affected by the seismic curve.

Abstract: This chapter describes the cracking of stainless steel piping under Inter-granular Stress Corrosion Cracking (IGSCC) conditions using probabilistic fracture mechanics that predict the impact of in-service inspection (ISI) programs on the reliability of specific nuclear piping systems that have failed in service. The IGSCC is characterized by a single damage parameter, which depends on residual stresses, environmental conditions, and the degree of sensitization. The Probability of Detection (POD) curves and the benefits of in-service inspection in order to reduce the probability of the leak for nuclear piping systems subjected to IGSCC were discussed. The results show that an effective ISI requires a suitable combination of crack detection and inspection schedule. An augmented inspection schedule is recurred for piping with fast-growing crack to ensure that the inspection is done before the cracks reach critical sizes and that the use of a better inspection procedure can be more effective than a tenfold increase in the number of inspections of inferior quality.

Abstract: Reinforced concrete structures are generally affected by degradation phenomena, which results in a time variability in strength and stiffness beyond the baseline conditions which are assumed in structural design, in particular when the concrete is exposed to an aggressive environment. Therefore, structural safety should realistically be considered time-variant. This paper provides a probabilistic approach to predict the time-evolution of the mechanical and geometrical properties of a reinforced concrete structural element (i.e., bridge pier) subjected to corrosion-induced deterioration, due to diffusive attack of chlorides, in order to evaluate its service life. The proposed model is based on Monte Carlo simulations in order to evaluate time variant axial force-bending moment resistance domains, with the aim to estimate the time-variant reliability index. Finally, an application to estimate the expected lifetime of a deteriorating reinforced concrete bridge pile is proposed.

Abstract: The current structural design provisions are prevalently based on experience and on the assumption of stationary meteorological conditions. However, the observations of past decades and advanced climate models show that this assumption is debatable. Therefore, this paper examines the historical long-term trends in ground snow load maxima, and their effect on structural reliability. For this purpose, the Carpathian region is selected, and data from a joint research effort of nine countries of the region are used. Annual maxima snow water equivalents are taken, and univariate generalized extreme value distribution is adopted as a probabilistic model. Stationary and five non-stationary distributions are fitted to the observations utilizing the maximum likelihood method. Statistical and information theory based approaches are used to compare the models and to identify trends. Additionally, reliability analyses are performed on a simple structure to explore the practical significance of the trends. The calculations show decreasing trends in annual maxima for most of the region. Although statistically significant changes are detected at many locations, the practical significance - with respect to structural reliability - is considerable only for a few, and the effect is favourable. The results indicate that contrary to the widespread practice in extreme event modelling, the exclusive use of statistical techniques on the analysed extremes is insufficient to identify practically significant trends. This should be demonstrated using practically relevant examples, e.g. reliability of structures.

Abstract: The paper presents the application of methodology for the assessment of reliability and structural load bearing capacity using advanced methods of probabilistic FEM analysis in combination with mathematical modelling of degradation processes of concrete and reinforcement. The durability, serviceability and ultimate limit states are assessed. The authors deal with the validation of load bearing capacity of the bridge on the 3^rd class road built in the 1^st quarter of 20^th century in the Czech Republic. Regarding the reliability requirements according to Standards and, considering the current state of the structure, the actual value of load bearing capacity is assessed. By reason of the time-consuming FEM analyses the stratified Latin Hypercube Sampling (LHS) method is used for generation of input random variables.

Abstract: The intensity of a product is regard as the degradation process during the whole product life, and as the confrontation process with the stress imposed on the product. Dynamic interfering strength theory proposed for structural reliability, we constructed the model for a element or a system in a continuous degenerate procedure varying with time t. A method of reliability evaluation is given for a kind of common sight strength and stress distribution.

Abstract: A KNN Classification Based MCS (Monte Carlo Simulation Method) is proposed for the reliability analysis which hindered by the implicit nature of the performance function. In the method, Markov chain is adopted to simulate a small amount of training samples, KNN classification is used to generate surrogate model of performance function, MCS is used to estimate the failure probability. An iterative algorithm is presented to improve surrogate precision dynamically in the region contributing to the failure probability significantly. The study results demonstrate that the proposed method has superior performance to the traditional response surface method.

Abstract: In this paper, the non-probabilistic reliability optimization problem of linear structural system with uncertain parameters described by interval models is proposed. The degree of the uncertainty is described by the size of the hypercube, and the maximum degree of variability the structure allows is measured by the non-probabilistic reliability index. The relation between the target of non-probabilistic reliability index and the fluctuation range of uncertain parameters is described by the geometric meaning of the reliability index. For the linear function, the uncertain parameters are expressed as the expression of the target value of non-probabilistic reliability index. Numerical example shows the validity and efficiency of the proposed method.

Abstract: A structural reliability analysis approach for uncertain structures based on a PSO-DE hybrid algorithm was proposed. In order to analyze the structural non-probabilistic reliability for structures with uncertain parameters, an optimization problem by using the convex model and the penalty function method was formulated. For better convergence speed and precision, the particle swarm optimization (PSO) algorithm and the differential evolution (DE) algorithm were combined to solve the structural reliability optimization problem, this PSO-DE hybrid algorithm was based on the evolution of the cognitive experience. The numerical examples were presented to demonstrate the effectiveness and accuracy of the proposed structural reliability analysis method.