Structural Reliability Studies Research Articles

Cable-stayed towers in transmission lines

Electrical energy demand is increasing with development of country where cities become more urbanized. It is necessary more generator plants remaining efficient systems. Many of these plants can not be installed near cities and the importance of lines transmission is a fact. They are important as far as plants, because they are a part of all energy system. All distribution is done to distant sites in an economical way making the minimum of environmental impact. The paper deals with analysis of transmission lines in cable-stayed towers, involving details of the design of a transmission line tower where modeling process of the structure is performed by Tower, an auxiliary software for structural analysis. A good design is a pledge of good functioning of energy distribution. Load tests to evaluate the structures behavior are showed. Recurring faults as wind action, cables rupture, and cascade effect, which cause damage to operation of the line are showed. Optimization methods for structural calculus are suggested. Structural reliability studies in order to improve the design as a whole and avoid future failures are also suggested.

Use of artificial neural networks in the prediction of horizontal and friction pressures in a slender silo

Structural reliability studies in silo pressure predictions are a subject of great interest because the number of variables in silo pressure calculations is large, which can generate numerous failures and occurrences of collapse. The objective of this study was to propose a pressure prediction model using artificial neural networks (ANNs) in comparison with experimental data. For data collection, a pilot silo model, proposed by Pieper and Schutz (1980), adopted by the German standard DIN 1055 (1987), was used. The pressure measurements were performed during loading and unloading of the silo. Smooth walls with flat bottom were used in the silo, varying the height/diameter ratio between 4, 6 and 8. The pressures observed on the silo walls were the horizontal pressures and the friction pressure of the product with the wall. The results of the pressures obtained experimentally were fed into an algorithm using multilayer Perceptron ANNs. The pressures measured on the silo walls were compared with the values predicted by ANNs, linear and polynomial regressions, and also with the values calculated by means of the European Standard EN 1991-4: 2006 and Australian Standard AS 3774 (1996). Among the models used, the best performance was obtained by ANNs, which were able to predict silo wall pressures with smaller errors.

Analysis of transmission lines towers of electrical energy

Electrical energy became crucial for a fully functioning in a modern society and research for development of the electrical system and transmission methods became essential. The paper deals with analysis of transmission lines towers, involving details of the design of a transmission line tower from the beginning until the end of line construction. Modeling process of the structure is performed by Tower, an auxiliary software for structural analysis. Load tests to evaluate the structures behavior are showed. Recurring faults as wind action, cables rupture, and cascade effect, which cause damage to operation of the line are showed. Optimization methods for structural calculus are suggested. Structural reliability studies in order to improve the design as a whole and avoid future failures are also suggested.

Considering the Yielding Displacement Uncertainty in Reliability of Mid-Rise R.C. Structures

In structural analysis and design, there are always uncertainties in determining loads and capacities. Structural reliability quantitatively considered uncertainties in analysis and design procedure. One of the well-known criteria to assess structural reliability is the Total Reliability Index (TRI) of structures. Yielding Displacement (YD) is an important component for calculations of TRI. Due to the changes in the analysis method, input type, normalization procedure, and the definition of target displacement, there are uncertainties in YD calculation. In structural reliability studies, both loads and resistance parameters are modeled as random variables. Therefore, the YD can be considered as a random variable. This study utilizes incremental dynamic analysis (IDA) to calculate TRI in mid-rise reinforced concrete moment resistant frames with intermediate ductility. The effect of uncertainty caused by YD is calculated based on pushover dynamic analysis. The reliability indices for the six structures of 3, 5, and 8 stories and three and five-span reinforced concrete moment frames show that the uncertainty caused by the YD reduces the TRI, but does not affect the seismic performance of the structure, significantly.

Optimization of Design Parameters for Materials Consumption for Reinforcing Metal Framework of Industrial Buildings

This study investigated optimum design methods for frame buildings with focus on minimization of economic costs. The methods discussed are intended to provide sufficient reserves for reliability of load-bearing steel structures. The analyzed mathematical models enable to assess seismic resistance of a structure and implement optimum design methods according to the selected key criterion. The available mathematical models assessing economic efficiency of metalwork reinforcement need further development. The model based on the principle of balanced risk is considered as the most appropriate for the study of structural reliability for industrial buildings. This model allows to assess the expected damage as compared with the initial spending on seismic protection. The focus is on setting and implementation of the task whose limiting condition provides equality between expenditures for reinforcement of damaged steel structures and those for damage prevention activities. Minimum of economic costs for construction or reconstruction of a structure is taken as the optimality criterion. This takes into account accumulation of damages within the standard life cycle and changes in stiffness of materials. Assessment of damage risk is based on the life cycle of a structure, its seismic resistance class and spending on damage repair. The study suggests a number of structural solutions that enable to reduce deformation of steel parts of the frame.

Structural Reliability Analysis of Wind Turbines: A Review

The paper presents a detailed review of the state-of-the-art research activities on structural reliability analysis of wind turbines between the 1990s and 2017. We describe the reliability methods including the first- and second-order reliability methods and the simulation reliability methods and show the procedure for and application areas of structural reliability analysis of wind turbines. Further, we critically review the various structural reliability studies on rotor blades, bottom-fixed support structures, floating systems and mechanical and electrical components. Finally, future applications of structural reliability methods to wind turbine designs are discussed.

Study of structural reliability of existing concrete structures

Structural reliability of buildings has become an important issue after the collapse of a shopping center in Riga 21.11.2013, caused the death of 54 people. The reliability of a building is the practice of designing, constructing, operating, maintaining and removing buildings in ways that ensure maintained health, ward suffered injuries or death due to use of the building. Evaluation and improvement of existing buildings is becoming more and more important. For a large part of existing buildings, the design life has been reached or will be reached in the near future. The structures of these buildings need to be reassessed in order to find out whether the safety requirements are met. The safety requirements provided by the Eurocodes are a starting point for the assessment of safety. However, it would be uneconomical to require all existing buildings and structures to comply fully with these new codes and corresponding safety levels, therefore the assessment of existing buildings differs with each design situation. This case study describes the simple and practical procedure of determination of minimal reliability index β of existing concrete structures designed by different codes than Eurocodes and allows to reassess the actual reliability level of different structural elements of existing buildings under design load.

Random vibration Monte Carlo simulation using multiple harmonic function schemes

The reliability study of structures under random vibration involves the performance of Monte Carlo simulation in time domain. One important part of such analyses is the generation of load time histories that must accurately represent the characteristics of the stochastic loads. There are several methods to generate time histories from a power spectral density (PSD) function. One common approach is based on the linear combination of harmonic functions with random amplitudes and fixed frequencies. This method requires considering numerous harmonic terms to simulate the target PSD function. In this paper, a new approach is presented to improve the performance of Monte Carlo simulation under random vibration when the excitation is represented by a PSD function. This goal is accomplished by refreshing the frequencies for every new time history of excitation. This can considerably reduce the number of replications that are required to perform a Monte Carlo simulation. The method is demonstrated through an example which involves a linear quarter car model.

Review on Calculation Methods of Structural System Reliability

In order to find a way to study the structure reliability further, the basic system of structural and the methods of analyzing were introduced. For the series system and parallel system, the calculation can be categorized into Point estimated method and interval estimated method. The point estimated method includes Stevenson-Moses method, Probability Network Evaluation Technique, Conditional Probability Method and Integrated Correlation Coefficient Method. The interval estimated method includes General boundaries of range and the narrow boundaries of range. The principle of method and the calculation steps methods were depicted in detail. This study has significance in theory and practice for the study of structural reliability.

Some elementary ideas concerning the complexity of system structure

A system of iid Bernoulli components is the starting point in the statistical theory of reliability. This simplification allows for the development of a rich, though elementary, theory for the structure of the system. Two representations play a prominent role in the study of structural reliability. One is the minimal path set representation and the other is the signature representation. By combining the two representations with the Gibbs measure for the state of components, one obtains terms that can be interpreted as the complexity of the system structure. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010

Confiabilidade de vigas metálicas dimensionadas pela norma brasileira NBR 8800

O estudo da confiabilidade estrutural se relaciona com a avaliação da probabilidade de violação dos estados limites para um sistema estrutural. Uma vez definidos pelo projetista os estados limites relevantes ao sistema estrutural, deve-se calcular o nível de segurança com respeito a esses estados. Nesse trabalho, é feito um estudo do nível de confiabilidade de vigas de perfis I laminados para o estados limite de flexão, projetadas segundo a Norma Brasileira NBR 8800 (1986) e seu projeto de revisão NBR 8800 (2003) através do método de confiabilidade de primeira ordem (FORM). São apresentados gráficos das variações do índice de confiabilidade (beta) em função do índice de esbeltez e, em seguida, é apresentada uma metodologia para uniformizar a confiabilidade, no domínio de um estados limite, através da adoção de procedimentos de correção do coeficiente de resistência.

Representation of uncertainty in maximum depth of marine corrosion pits

Pitting can be a critical form of corrosion for mild and high strength low alloy structural steels subject to saline environments. For pipelines, tanks and nuclear and other containers perforation is the main design criterion. The present paper outlines a recently developed model for the progression of ‘maximum’ observed pit depths, based on new field trials using conventional coupon testing. The variability of the maximum pit depth and its changing behaviour with time of exposure is an important aspect for structural reliability studies. The most common approach uses the Gumbel distribution. However, recent data for mild steel reveals inconsistencies. These are described and have been noted also for pitting in some other metals. It is proposed that proper account has not been taken of sample inhomogeneity and, more importantly, that extreme pits are unlikely to be independent events, even asymptotically, as required by extreme value theory. A much simpler approach based on structural systems reliability theory is proposed. This has important practical implications for extrapolation to larger areas of steel plate or for long-term exposures, such as for nuclear containers.

Theoretical Joist-Rupture Sequences in Wood-Floor System Model

The mechanical behavior of wood is strongly dependent on factors such as species, grade, moisture content, and member size as well as on time effects such as duration of load and creep. Time-dependent phenomena, combined with the variability inherent in a biological material, make it challenging to definitively evaluate the long-term performance of wood structures in general through experimental testing programs. In analytical studies of wood systems, damage accumulation and viscoelastic stress-strain models have been used to account for time-dependent effects. Recent structural reliability studies on wood systems have used these types of models to include time-dependent phenomena in the assessment of reliability indices for various strength and serviceability limit states. Structural reliability studies produce a notional estimate of the expected frequency of exceedance for a particular limit state, but they do not reveal information on the process leading to that limit-state failure. In the present study, the performance of light-frame–dimension lumber wood-floor systems is investigated using a time-dependent Monte Carlo simulation for combined dead and occupancy live loads throughout a 50 year design lifetime. Particular attention is paid to the relative frequency and temporal characteristics of joist ruptures predicted by commonly accepted duration-of-load models. The results of the study provide insight into probable long-term wood-system behavior and can help to further the development of appropriate design, inspection, and maintenance procedures.

Structural reliability analysis method for viscoelastic members

The structural performance of viscoelastic materials may be strongly dependent on the temporal characteristics of the applied loadings. This time dependence cannot be properly considered in structural reliability studies using the conventional analysis techniques such as first-order, second-moment methods. However, Monte Carlo simulation can be adapted for this purpose provided time-dependent stochastic load models and stress-strain models are available. In this paper, a structural reliability analysis method is presented which includes both time-dependent structural loads and material response. The application of the method to a reliability analysis of a deflection serviceability limit state is presented for illustration.

Simulation technique for tropical cyclone occurrences

In a hurricane or typhoon-prone region, the prediction of tropical cyclone occurrences is an essential element in structural reliability studies. The uncertainty of tropical cyclone generated extreme winds that affect tall structures is currently being undertaken at the University of Hawaii at Manoa. In order to understand the long-range behavior and the patterns of tropical cyclone occurrences, a Monte Carlo method-based simulation technique is investigated. In this approach, the probability distributions of the interarrival time between occurrences of tropical cyclones, the probability distributions of the arrival times of the first as well as the last tropical cyclones of each typhoon season, and the probability distributions of the durations of typhoon seasons are the basic elements in this simulation process. An application of the approach to Shanghai, China data is illustrated.

Simulation technique for tropical cyclone occurrences

In a hurricane or typhoon-prone region, the prediction of tropical cyclone occurrences is an essential element in structural reliability studies. The uncertainty of tropical cyclone generated extreme winds that affect tall structures is currently being undertaken at the University of Hawaii at Manoa.In order to understand the long-range behavior and the patterns of tropical cyclone occurrences, a Monte Carlo method-based simulation technique is investigated. In this approach, the probability distributions of the interarrival time between occurrences of tropical cyclones, the probability distributions of the arrival times of the first as well as the last tropical cyclones of each typhoon season, and the probability distributions of the durations of typhoon seasons are the basic elements in this simulation process. An application of the approach to Shanghai, China data is illustrated.

Predictive distribution of strength under control

The joint distribution of strength of materials is derived in terms of a set of conditional distributions to be used in studies on structural reliability. Bayes theorem of probability theory is used to update prior distributions for the parameters of Gaussian sequences by direct observations and/or by compliance tests. Maximum-Likelihood estimators are given for the efficient quantification of prior information. The formulae are applied to concrete production judged by standard tests. It is shown that statistical uncertainties must not be ignored in structural reliability studies.