RELIABILITY ASSESSMENT OF WELDED STEEL DETAILS IN BRIDGES USING INSPECTION

Civil infrastructures are in many countries ageing and maintenance is necessary in order to secure mobility and safety for the inhabitants in the coming years. The maintenance and repair actions for these structures should be planned optimally in order to reduce the total life cycle cost for the society. However, a minimum reliability level should still be secured in order to reduce the risk of human lives. In the present paper a probabilistic fracture mechanics model is presented in order to estimate fatigue crack growth in welded steel details [1]. The probabilistic model is based on linear elastic fracture mechanics and uses a bilinear version of Paris law by which the influence of small to medium size stress cycles can be modelled accurately. This is especially important for bridges where many of these stress cycles are observed due to the traffic load. Additionally, the model takes the influence of misalignment in the welding into account along with bending stresses. Both misalignment and bending stresses can have a significant influence on the number of cycles to failure. The probabilistic model can then be used to estimate the reliability of a welded steel detail in a bridge. However, in the present paper the probabilistic model is used to rational planning of the operation and maintenance strategies where information about the crack size, at a given point in time, is used together with information about the probability for detecting cracks [2]