Reliability Analysis Of Existing Bridges Considering Proof Load

Due to the external environment erosion and growing traffic flow, many of the existing bridges'reliability have reduced in the service period, the identification and correct reliability assessment of bridge capacity has become the safe guarantee of structure in the future.The reliability of existing bridge is different from structural design. first, the resistance of structure is attenuated as time going on; secondly, the existing bridge has experienced validation of service load, the subsequent information that obtained from the service process can be used to structure parameter modification , thus making the reliability evaluation more accurate. so far, the reliability calculation of the existing bridges are usually considering the attenuation of resistance, but rarely considering the proof load. According to the current situation, this paper mainly do the following job:1,Based on the predecessors' achievements, the random process model of resistance, the according mean function and the deviation function are discussed; Vehicle running state can be divided into general running state and intensive running state, there the distribution function of vehicle load's maximum effect during its design service years are established respectively, which has considered the dead load of the normal distribution model and the non-normal distribution model of vehicle loads.2,Combined the load model of existing reinforced concrete bridges and the maximum distribution function of any assessment period, the distribution function of vehicle load's maximum effect under changes of traffic flow and design specification are presented here, and so the values of automobile load effect; with the resistance discretization method, combined with the resistance model and its decay laws, a time-varying reliability of the existing bridges are calculated and analyzed.3,In this paper, the principle of validation load method and conditional probability method are described, and the resistance model that under proof load is established. Through a example, the influence of proof load to structural resistance and reliability index which take no account of resistance degradation is analyzed, and the parameters sensitivity is analyzed, too; combined the existing time-variant reliability method with conditional probability method, the author obtains a promotion methods that can consider both resistance degradation and proof load.4,The concept, classification and evaluation criteria of structures'remaining service life are discussed, and a prediction method for existing bridges during its remaining life that based on bearing capacity criteria is introduced; with the time dependent reliability curve of example in Chapter IV , the remaining Life of a existing bridge is predicted.