The influence of the transverse distribution of loads in fatigue life of bridges

Most bridges that were built during the 1960s - 1980s were mainly designed in prestressed concrete. Nowadays, they represent about the 95% of the total number of bridges that are part of the Italian national transport network under the responsibility of private and public management companies. Existing bridges are naturally subjected to degradation mechanisms during their service life, due to environmental and operational events, leading to a decrease in performance, if also mechanical problems related to the transversal distribution of loads are added to this, serious problems can arise. It is important to underline that the development of stresses and the transfer of loads in a beam bridge is directly related to the relationship between transverse beams and longitudinal beams, in fact, the main structural function of cross-beams is to allow the correct transfer of loads in the transversal direction from the point of application of the load to the neighbouring beams. Improper mechanical interaction between the two elements leads to an insufficient transfer of loads, leading to a concentration of stresses generally applied to the edge beams. The goal of this Thesis, developed with the collaboration of the engineering company Masera Engineering Group, is to investigate the role of the transverse beams of an existing beam bridge in order to study the effective grade of loads transfer and to evaluate the fatigue behaviour and the residual fatigue life of the structure.