Fatigue life research of welded joints in railway girder

Abstract

Progressive crack formation in welded joints of railway girders requires a reliable prediction of the fatigue life. It was found that the most common fatigue cracks are T-9 and T-10, which are formed in welded joints of vertical stiffeners to the beam web. The service life calculation of such joints, according to guideline, shows overestimated results. To reduce the error, the operational features of these joints were investigated under a moving loads. Stress-strain monitoring was carried out with the help of a small-sized automated tensometric complex «Tensor-MS». In total, 13 trussed and solid-web girders were investigated. As a result, it was found that the beam web near the welded ends of stiffeners subjected to bending deformations, but fatigue curves, obtained under tensile-compressive, are used to calculate the durability of such joints. To increase the reliability of fatigue calculation, laboratory tests were carried out for a high-cycle fatigue of welded specimens, simulating joints with T-9, T-10 cracks. The design and materials of laboratory specimens were assigned similarly to that of the main beams or the floor beams. Analysis of the actual stresses under the moving load revealed the necessary loading conditions for laboratory specimens. Totally, 42 laboratory samples were tested for bending. As a result of the tests, fatigue curves of welded joints were obtained. The results show a decrease in the joints durability by 20–50 % in comparison with the samples tested in tensile-compressive. In addition, as a result of the tests, the dependences of the fatigue cracks growth rate on the maximum cycle stresses were obtained.