FATIGUE BEHAVIOUR OF RIVETED AND BOLTED CONNECTIONS MADE OF PUDDLE IRON - PART II: NUMERICAL INVESTIGATION

In Europe and North America there are a number of old riveted highway/road and railway bridges, constructed during the second half of the 19 th century up to the middle of the 20 th century which, due to economic reasons, are still in operation. Since they have been subjected to increasing traffic intensity along their operational lives, both in terms of vehicle gross weights/axle loads as well as truck/train frequencies, their damage levels need to be assessed in order to decide about possible repairs. Thus, the maintenance and safety of these existing bridges is a major concern of governmental agencies. In order to assure high safety levels in old riveted steel bridges, highway and railway authorities have to invest heavily in their maintenance and retrofitting. Fatigue failures are a concern for riveted steel bridges since they were not originally designed taking into account fatigue. The fatigue phenomenon was only intensively investigated after the half of the 20 th century, when the riveted construction was no longer applied in new bridge structures. Therefore, there is a lack of a comprehensive methodology for the fatigue assessment of riveted bridges motivated by limited knowledge on the fatigue behavior of this type of construction as well as a deficient understanding on the fatigue behavior of the old materials (wrought-iron, puddle iron or old steels) and riveted connections. This paper presents a numerical study concerning the fatigue modeling of riveted and bolted joints made of puddle iron from the centenary Portuguese Fao bridge. A finite element model is proposed using solid and contact finite elements. The effect of the clamping stresses is taking into account on the model as well as friction. The fatigue crack initiation and propagation are both modeled using, respectively, the local strain and Fracture Mechanics approaches. Numerical S-N curves are predicted and compared with the experimental data available for the investigated joints.