There are a number of bridges which are designed according to codes without seismic provisions being considered. Such bridges are mostly found deficient and may need seismic retrofitting. Bridges that were built before the 1970 S, either in the USA or Japan or Europe, were designed with little or no consideration for seismic demands. The majority of these bridges are supported on reinforced concrete bents at the abutments and pier walls that lack the ductility and strength to resist earthquakes. Besides most of these bridges have short spans (6-18 m) to medium spans (18-90 m). A bridge with a short span may be built with timber girders or with a concrete slab superstructure, whereas a bridge with a medium span is often built with steel girders, precast concrete girders, or cast-in-place box girders. Bridges in general consist of two structural components: a superstructure including the elements above the support and a substructure including the elements that sustain the superstructure. In this paper, the retrofitting of an existing short bridge is discussed; it is situated in Treviso (a town in the Venice area) near the vital new airport "Antonio Canova". Retrofit consists of building a new semi-integral bridge type with micro-piers on the bridge heads.
