Bridge Bearing Capacity Assessment Methods Based On Probability Theory

With the growth of the bridge service time, due to the environmental corrosion and the increasion of traffic, gradually produce structural function decline phenomenon, its reliability will be reduced. Capacity of existing bridge structure identification and structural reliability assessment is to ensure the safe use of the next service period of the premise.The role of the structural variation with time, the resistance of the structure as a random variable. In addition, the structure of the load effect is due to the different service evaluation period change over time. On the other hand if the bridge has undergone a particular load verification function, its results can be used to structure the data parameter correction, so that the structural reliability assessment is more realistic. For these situations, the paper made the following tasks:(1) Summarizes the structural reliability of the basic concepts, principles and calculation of reliability index commonly used methods. (2) Model based on constant load vehicle load model, at home and abroad on the basis of a variety of survey data to study the concrete bridge load effects model. (3)Reliability index calculation method based on using the JC method Xisupu bridge superstructure reliability were calculated and analyzed. The main sections are larger than the target reliability index Reliability 4.7, determine the work bridge safety, that is consistent with the requirements of the current national standards. (4)According to time-varying reliability theory predicts Xisupu Bridge in the subsequent period of service reliability indices. Reached the useful life requirements, and set aside a certain amount of safety and reliability of the existing bridge structure with the structure of the growth in constant service time reduced. (5) Introduces the basic principles of proof load by a bridge load test data provided by direct inference on the structural resistance, and thus the safety of the structure to make a reasonable evaluation method. Attenuation in the authentication load and resistance factor of two, the resistance degradation effects on more significant structural reliability; prove structural reliability considering resistance decreased after the change, the more harsh environmental conditions, the greater the degree of structural reliability is reduced and may does not meet the target reliability requirements. (6)By example calculation and theoretical analysis, pointing out structural reliability proof load increases, mainly because of the impact of the effective resistance of the tail amputated, proof load resistance of the structure as a method of direct sexual inference method, with theoretically superior.The results show that:Time-variant structural reliability theory is used for the existing bridge safety assessment,structural engineers can not only make the current situation better understanding, you can also make the relevant administrative departments of the service conditions of the structure and approximate future projections, and based on the results of time-variant reliability assessment development of bridge health monitoring system. According to the different structure we need the actual service environment to select the appropriate resistance to decay law, the successor of the structure served correctly assess the reliability of the period, and then use a reliable indicator of the variation of the structural repair and reinforcement to develop a reasonable solution. On the other hand, when considering the reliability verification loads analysis, validation due to structural reliability analysis method based on non-destructive load verification load test on the basis of structural reliability and allows, under certain conditions improved, so this method has a good application prospect. Also exist, such as the face of the actual test methods, evaluation of test results and other issues, the need for further research and practice.