Stochastic Seismic Reliability Analysis Of Girders Of Long-Span Multi-Pylon Cable-Stayed Bridges

The built large span multi-tower cable-stayed bridge has an important position in the traffic system, it has large spanning scale and the complex system structure, thus scientific and reasonable seismic design and analysis is currently an important topic. As an important part of seismic theory, the seismic reliability analysis theory has made great progress, but for large span multi-pylon cab random seismic reliability analysis of cable-stayed bridge tower is still less research. Based on the built Jia-shao Bridge across the river as the research object, considering the two aspects of seismic excitation and structural parameters of main girder of randomness, establish its reliability analysis method, and the random earthquake girder is reliability index, to evaluate and analysis. The main content of this article is:1. Firstly, system combing the structure random seismic reliability analysis method, including the reliability of the random vibration theory and stochastic analysis method of two parts. The former including the ground motion input, processing seismic spatial effect model and random seismic response spectrum method, which includes random seismic reliability analysis principle and the theory of structural reliability analysis.2. By establishing a finite element model of Jia-shao Bridge, and analyzes the dynamic characteristics, understand its vibration mode distribution characteristics, and further to determine the stiffness characteristics of salt bridge. Selected main girder elastic modulus, poison ratio and quality to analyze its influence on the dynamic characteristics of the bridge, the calculation results show that the three sensitive factor is the dynamic characteristics of the bridge, including the influence of elastic modulus and the quality of main girder is more sensitive.3. Random vibration method is used to solve the salt bridge under random seismic response, compared the different responses of Hu Yu-xian spectrum model, Ou Jin-ping spectrum model and Du Xiu-li spectrum model, consistent with the three-dimensional excitation to the one-dimensional uniform excitation response result comparison, as well as considering the traveling wave effect of ground motion and coherent effect on the result of the response.4. Basing on the current bridge seismic design code, and for the first time mechanism set up corresponding function and the limit state function, and using the response surface method, the random vibration analysis for different sample points and the response as a result, the fitting out the explicit expression of the function of the main girder structure function, finally with classic moment method to analyze its reliability. Structure shows that main girder under random seismic load, structural parameter randomness has a large influence on reliability index; Salt bridge girders under random seismic load, the structure of the rules and regulations of the reliability indexes meet the target reliability requirements, so as to prove that salt bridge girder under the design seismic action with sufficient security.