Bridge Ultimate Load, Based On Fracture Mechanics Analysis

With the development of communication, a great deal of new-build bridges need to be evaluated, at the same time ,a great deal of service bridges need to be load exalted or maintained and reinforcement, which makes it important to evaluated the service bridges' bearing capacity. At present, kinds of methods of finite-element analyzing bridge structure's limit bearing capacity for concrete's complex stress nature get the concrete's constitutive equations and destructive criterion by fitting regression line. Kinds of finite-element models have more or less deficiency for the material's complex character, which leads to the bigger deviation of the calculated numeric value, so it is limited in the range. Besides, the current bridge and culvert design criterion takes some basic postulation during the calculation of the bridge's member in bending, which results in over-conservative numeric value.The paper compared different macrographs fracture mechanics models by fracture mechanics, and got the finite-element analysis model-crack band model which is fit for concrete. Based on crack band model, the finite-element structure analysis program-"Bridge's Bearing Capacity Analysis System" is programmed .Using this program, the author calculated a test beam's limited bearing capacity. Compared the calculated numeric value with the laboratory numeric value, it is proved that the program is basically accurate. Meanwhile, compared the result with the numeric value which is calculated according to the current bridge and culvert design criterion, it is proved that the latter is too conservative.