Papers by Keyword: Failure Probability

Abstract: The correlation of failure modes needs to be considered in the reliability analysis of foundation excavations system. Because it is difficult to calculate the correlation coefficient of failure modes, the computational efficiency of traditional method is low. In this paper, the response surface (RS) is established by using the uniform test and support vector machine (SVM). On this basis, in order to obtain the index of each failure mode, the random parameters generated by Monte Carlo simulation are predicted. Combined with the Pearson correlation analysis, the correlation coefficient of failure modes is obtained. And then, the Breadth Border Method, Narrow Bounds Method and PNET method are used to calculate system failure probability of foundation excavations. The reliability analysis method of the foundation excavations system based on the response surface of the support vector machine (RSSVM) is put forward. The instance analysis shows that the method is simple in calculation, and provides a convenient way for the system reliability theory of foundation excavations.

Abstract: Tower crane as the main equipment of building trades, the failure of Hoisting mechanism is particularly important for complete machine working performance and device safety. In this paper, the failure of tower crane hosting mechanism is analyzed, the failure mode of hoisting mechanism is researched, the failure probability of hoisting mechanism is built, the various factors in the work influence on the tower crane hoisting mechanism is analyzed, use coefficient modification method to correct influence factor of hoisting mechanism, according to the series system theory to calculate the failure probability of tower crane, Provide the basis for the whole risk assessment.

Abstract: Risk analysis is an important part of the dam safety risk management. The uncertain factors causing the failure of the gate is very complex, including the gate design and manufacturing, management operation, some man-made factors, etc. The traditional risk analysis method has certain limitation. Bayesian networks can quickly and effectively solve the failure probability of the system and for a direct analysis on the effects of every system component by a two-side inference, so as to locate the system weakness and adopt effective measures. This paper based on Bayesian network, through the example of Bayesian network in the application of dam gate risk analysis.

Abstract: The excavation of foundation pit will change the initial stress state in surrounding soils, which induce the superimposed stress and uneven settlement to the adjacent existing tunnels. Based on the pit excavation engineering in Shenyang, which sits atop the existing tunnels, the risk factors and failure type of shield segment lining were studied through risk analysis theory. According to the uncertainty and spatial variability of soil parameters, the risk accident of existing tunnel was calculated by means of stochastic finite element which is combined Monte Carlo simulation with FEM. The risk of existing tunnel during the pit excavation stage was evaluated respectively under multi-failure patterns. The framework is used to estimate and minimize risks at pit excavation engineering in Shenyang.

Abstract: The response surface method is adopted to analyze the structural reliability. This paper presents a new response surface method with the uniform design method to predict the failure probability of structures. It is the response surface method based on Fourier orthogonal basis function (RSM-Fourier). To reduce computational costs in structural reliability analysis, approximate Fourier response surface functions for reliability assessment have been suggested. The method involves the selection of training datasets for establishing a model by the uniform design points, the approximation of the limit state function by the trained model and the estimation of the failure probability using first-order reliability method (FORM). The proposed method is applied to examples, compared with other methods to demonstrate its effectiveness.

Abstract: To analysis the reliability of Dongjiang Bridge, a steel truss bridge stiffened with rigid cables, a new analysis method that combined with each advantage of some common reliability computing method was put forward, which could get the probability distribution and numeric attributes of complex bridge structure's response expediently, and then get the reliability index and failure probability. A stochastic finite element model was established to analyze this bridge, in which some parameters such as material, geometric dimensioning, loads, and so on, were simulated as stochastic variables. The analysis result show that the lowest reliability index of main member bar's stress is 5.10, more than the allowable value 4.7, and the corresponding failure probability is 1.71×10-7. The reliability index of mid-span deflection in serviceability limit states reach up to 6.99 and its failure probability is 1.53×10-7. All results indicate that the strength and stiffness of Dongjiang Bridge has higher reliability.

Abstract: The randomness of value of tuned sub-structure mass and rigidity is comparatively large because of the needs of actual projects. Based on the dynamic characteristics and reliability of MSCS, the seismic response of the mega structure and the overall failure probability are discussed with the value of tuned sub structural mass and rigidity under different seismic intensity. It is shown that tuned sub structural mass and rigidity have significant affection on the overall reliability of structure, and seismic intensity has not interfere this regular pattern. Therefore, structural parameters of optimization which are referred to the regular pattern should be considered in the actual design in order to further enhance seismic capability of MSCS.

Abstract: In order to depict the complex uncertainty involved in evaluation of equipment sensitivity to voltage sags, the voltage tolerance level of sensitive equipment is characterized by interval data, a evaluation model is proposed to derive interval probabilities of equipment operation status. Hybrid entropy is used to measure the uncertainty of randomness and fuzziness. Then, the interval result is transformed into point-valued probability based on maximum hybrid entropy model. By the help of personal computers, the proposed model is finally verified in a test distribution system.

Abstract: It is difficult to assess the impact of voltage sags on sensitive equipment because of the complex uncertainties involved in voltage tolerance capability. Determining the distribution regularity of voltage tolerance capability is an important step in voltage sag sensitivity assessment. Computers’ voltage tolerance capability are obtained through laboratory tests. The point-value distribution function of voltage tolerance capability is calculated by Maximum Entropy Principle and then the interval probability distribution function is derived based on confidence interval, so as to derive an interval probability of equipment failure probability. The proposed model is finally verified in the IEEE-30 bus system. The results are compared with that of stochastic estimation method, showing that the proposed method can reflect actual conditions better and obtain accurate result.

Abstract: A new criterion (failure stress criterion) is presented for the mixed-mode fracture of concrete by comprehensively evaluating several mixed-mode crack criteria. The new criterion absorbs some results fitting in with concrete from G.C.Sih and Erdogen’s maximum circumference stress criterion and G.C.Sih’s minimum strain energy intensity factor criterion. It combines concrete material fracture property with the condition of loads at the moment of concrete fracture by Weibull theory. It is concluded that concrete crack expands neither along the direction of maximum circumference stress nor along minimum strain energy factor S. The crack extends along the direction limited in the area controlled by two criteria. The accurate crack position is determined by failure probability of the strength of concrete structure. The experimental results indicate that the new criterion has better precision and adaptability comparing with other criteria and it can be applied to engineering very well.