Papers by Keyword: Time-Dependent Reliability

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Authors: Peng Fei Xue, Da Ling Mao
Abstract: A multi-factor diffusion model of chloride in concrete was formulated, in which the hypothesis of Fick’s Law were corrected through parameter definition. The values of the parameters in the model were given for practical applications according to pilot calculation and analysis of mass data. By using this diffusion model, three calculation methods of concrete structure service life were further deduced, it includes definite value method, probability performance based method and time-dependent reliability based method. The service life prediction for the approach bridge of Huang-pu Bridge was carried on by using various prediction approaches mentioned above. The results showed that: time-dependent reliability based method can consider randomness of chloride diffusion coefficient and the depth of concrete covering layer, and the stochastic characteristic of environment variable can be easily taken into account too. By adjusting the target reliability, the prediction results are consistent with those of the other two methods.
Authors: Amandeep Singh, Zissimos P. Mourelatos, Jing Li
Abstract: Reliability is an important engineering requirement for consistently delivering acceptable product performance through time. As time progresses, the product may fail due to time phenomena such as time-dependent operating conditions, component degradation, etc. The degradation of reliability with time may increase the lifecycle cost due to potential warranty costs, repairs and loss of market share. In design for lifecycle cost and preventive maintenance, we must account for product quality, and time-dependent reliability. Quality is a measure of our confidence that the product conforms to specifications as it leaves the factory. Reliability depends on 1) the probability that the system will perform its intended function successfully for a specified interval of time, and 2) on the probability that the system response will not exceed an objectionable by the customer or operator, threshold for a certain time period. Quality is time-independent, and reliability is time-dependent. This paper presents a methodology to determine the optimal design and preventive maintenance of time-dependent, multi-response systems, by minimizing the cost during the life of the product. The lifecycle cost includes a production, an inspection, and an expected variable cost. All costs depend on quality and/or reliability. A roller clutch example highlights the design methodology for lifecycle cost.
Authors: Qiang Qiang Jiang, Hui Peng, Chong Yang Zheng, Qin Long Yan, Shuai Liu, Guo Dong Ma
Abstract: The correct and reasonable calculation of the structural reliability is the theoretical basis of the design, construction and use of the structure. The research is focused on the development of computing methods of reliability of structural members and system, and also points out the merits and problems of the existing methods with respect to the analysis of the present researches on structural reliability. Meanwhile, the summarization of the development and the existing problems on the reliability of time dependent structure has been provided. Furthermore, it proposes that correlation is the common problem in the computing of structural system reliability, and probes into the correlation coefficient of the calculation and the effects that correlation coefficient exerts on random variables and different systems. The conclusion shows that the specification of the adaptation range of calculation methods and reducing the effects of correlation coefficient contribute to the insurance of the structural safety.
Authors: Ke Ke Peng, Pei Yan Huang
Abstract: Based on time-dependent reliability theory, intermediate working state is considered, combining with current specifications, concrete filled steel tubular (CFST) arch bridge is discussed as a case, determination principle of three-stage mode is given. The direct correspondence from reliability indices to working states is made clear consequently. Introducing state variables, dynamic Monte-carlo method is presented. Basic formulas of failure probability and damage probability are derived by variable time increment method. The bridge is an CFST arch bridge with 83.6 meter-span, which operated for 10 years. According to test result, dynamic Monte-carlo method is used to estimate the reliability of this bridge. The analysis result shows that, in the tenth year, both damage reliability index and failure reliability index are above target reliability index. The example bridge is in safe working state at present. This conclusion is consistent with the facts.
Authors: Feng Qi Guo, Zhi Wu Yu
Abstract: The remaining service life of reinforced stone arch bridges is of great concern to management and conservation units. It is also the scientific basis for decision to next reinforced maintenance or rebuild. The concept of time-dependent reliability is introduced. Accoding to the most common section enlargement reinforcement method, the load and resistance of the structures are analyzed. The analysis methods and steps of life prediction are proposed, and the remaining service life is obtained. Based on above methods, an engineering example is given, the service life forecast calculation of reinforced stone arch bridges is discussed.
Authors: Da Gang Lu, Xue Ping Fan, Dong Fang Li
Abstract: Based on the characteristics of existing structures, the analyses were presented for an effect on the resistance of existing structures by using deterministic loads and stochastic loads. The calculating equations of the normal distribution and logarithmic normal distribution resistance under the deterministic proof load and the stochastic proof load were presented. Some valuable conclusions have been obtained for the calculating reliability of the existing structures. Based on the conclusions, time-dependent reliability model of the existing bridges was updated, the time-dependent reliability indices were solved with time integrated-discretized approach, and finally the numerical examples were presented.
Authors: Jun Tao Kang, Nan Wang, Yun Jiang Huang
Abstract: The reliability of existing double-curvature bridge strengthened with augment section method is put forward based on time-dependent reliability theory. The concerned statistical parameter is taken by using the finite element software. First-order second-moment method is used to evaluate the reliability indexes which estimate the working state of the structure. Combined with a practical example, the time-dependent reliability is illustrated.
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