Heath Monitoring And Evaluation Of Fatigue Life For The Existing Bridge

One of the main modus of bridge damage is fatigue failure, especially in recent years, the traffic volume increasing and the speed continues to improve, so fatigue life assessment of bridge has a very important meaning and function. Welding structures not only have complex shape, but more important is the phenomenon of stress concentration protrusion. Therefore, finding better fatigue life evaluation method is more important.This paper uses the strain field intensity method and nominal stress method to assess the fatigue life of welded steel structures, and the main contents are as follows:First, using ANSYS built I-type steel beam, determined the dangerous parts of the structure and get the stress and strain history of the dangerous point. In the process of modeling in order to more close to the real situation of welding defects in welds, dug holes to simulate the welding defect. The position of the small hole is different, respectively using o legrees,45degrees,90in the horizontal plane. With a different point of view to illustrate the welding position influence on fatigue life.Second, using rain flow counting method adds up monitoring data (because this paper/erified the feasibility of the strain method, so this paper is known in the monitoring data on he basics of checking). The basis of the nominal stress method is the S-N cure of the I-shaped)eams, and combined with Palmgren-Miner linear cumulative damage theory to calculate the Iangerous point of fatigue life (that is using nominal stress method to estimate the fatigue life)f the components). The fatigue life of components was calculated for different holes.Again, used the K. N. Smith damage equation and based on the strain field method to (?)alculate the fatigue life of the structure. In order to more finely division unit, introduced the ubstructure technique in the process of using ANSYS elastic-plastic finite element analysis. Jsing substructure technique divides cell, so improving the accuracy of the fatigue life.ssessment. This article also discussed the influence of different field size in the sub-structure nodel.Finally, the calculation results of the strain field intensity method and nominal stress aethod proved that the strain field method can improve the calculation accuracy. The strain ield method to assess the fatigue life of the structure has a certain practical value.