Structural integrity assessment of the cast steel upper anchorage elements used in a cable stayed bridge

摘要

This paper presents the structural integrity assessment of the cast steel upper anchorage elements of a cable-stayed bridge, which presents numerous fabrication defects. One of the elements failed in 2000. The assessment is performed by using Failure Assessment Diagrams (FADs), includes the effect of residual stresses and considers three different types of defects: postulated surface semi-elliptical cracks (with three different aspect ratios), an existing elliptical embedded crack, and an existing surface semi-elliptical crack. These last two represent two actual defects found in the material. Moreover, two loading hypotheses are also considered: one caused by a 30 year prediction of the ordinary traffic conditions, with a 6% annual increment, and another one caused by the loads produced by the total weight of four heavy trucks crossing the cable-stayed bridge. Material tensile properties were obtained using the ASTM E-8 standard, whereas fracture properties were obtained using the ASTM 1820 standard for both cracked and notched conditions. The results reveal that the anchorage elements work under safe conditions only if the first hypothesis is considered and no residual stresses are taken into account. In case of the second hypothesis, the conditions are unsafe even for null residual stresses.