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Problems and Innovative Solutions in Retrofitting and Enhancement of Existing and Historical Railway Steel Bridge

Many existing steel bridges of the railway network are significantly old, sometimes ancient and even historical. They continue to be in use for different reasons but require retrofitting works to be preserved or to be safely operational. The paper deals with two emblematic cases of such bridges. The first one is a historical iron bridge built in the last decades of 19th century. It consists of a slender parabolic grid arch having a span of about 150m sustaining a boxed beam having a total length of 266 m with a lower railroad deck and an upper roadway deck. The bridge is very amazing for both the aesthetical aspect and the engineering concept. The second bridge was rebuilt immediately after WW2 and represents a typology largely present along the Italian railways. It has three spans of simply supported steel truss beam, for a total length of 142 m. The paper illustrates the works able to increase the residual service life considering various options for the future use. The retrofitting strategy, the enhancement level, the constructive solutions, sometimes very innovative, are critically discussed with the aim of a generalization of the proposed scheme, paying some attention to the cost/effectiveness ratios.