Reliability Analysis Of Truss Bridge Structural System And Recognition Of Component Importance

Focusing on a railway truss bridge designed following "allowable stress" method, basing on "structural system's performance-base" concept, analysis the structural system's probability of system's linear effect and nonlinear effect. First try to research the structural system's probability level which is designed following "allowable stress" method. At the same time put forward a theory-possible and implement-easy method which can be used to research structural system's probability. The main work is as following,First, build up the FEA analysis model according to the design parameter of a railway steel truss bridge that is designed on the basis of "allowable stress" concept and make a brief analysis on the effect under corresponding load. Then do the probability analysis of two structural system's performance index (maximum stress and maximum deflation) using the Monte Carlo and influence surface methods in the condition that the random input variables are varying. Obtain the probability index under performance at different level. And compare with probability level of civil building structure; get the preliminary understanding about the railway steel truss bridge's probability level designed following "allowable stress".Secondly, combining the nonlinear FEA and influence surface method, calculate the structural system's ultimate strength reliability. According to the characteristic of central composite influence surface method, acquire the distributing samples that the main input random variables are locating on central point, axial points and conner points, then conduct independent and repeat nonlinear FEA analysis according to each set of sample, obtain the ultimate strength of structural system corresponding to this condition. Fit out the bearing capacity limit state equation according to ultimate strength results. Get the reliability index of ultimate strength.At last, on the basis of finite-differencing sensitivity method, refer to the idea which is purposed in"study of components'weight coefficient in structural system's reliability evaluation"by Haicheng Rong and Jianxun Ma. Led to a decline in structural system's reliability through increasing the load on truss joints, define the components'weight coefficient by the reducing degree of reliability. Then determine the importance level of components according to components'weight coefficient. And sort them according to their importance in the overall structure.