Performance of retrofitted steel structures subjected to fatigue loading

![CDATA[Steel structures today are edging towards the end of their design life, as the frequency and magnitude of loadings are becoming significantly greater in comparison to the initial design loads at the time of construction. Deterioration from prolonged exposure to environmental conditions including weathering and climate change, as well as the effects of human error, also influence the design life of these older steel structures. This paper will focus on developing a comparison between the fatigue performance of old and new steel structures. The fatigue resistance of both the old and new steel structures is evaluated by investigating and analysing the stresses at critical locations within the structures. Retrofitting techniques are applied to both the old and new structures and analysed in terms of their capacity to increase resistance to fatigue failure and extend the design life of steel structure. The research herein consists of both experimental studies and numerical analysis. Fatigue induced cracking is introduced into the FE model to investigate the post-damage performance of the old and new structures. Retrofitting methods are introduced into the FE model to investigate improvements in the fatigue performance of the old and new girders. An overall conclusion determines the extent of increasing design life, enhancing profitable engineering and focus on sustainability in terms retrofitting an old structure.]]