Retrofitting of the truss girder of a pedestrian bridge in Eraclea, Venice

The following paper illustrates the retrofitting of a new built footbridge constituted by a couple of steel truss girders adjacent to an existing concrete arch bridge in the town of Eraclea, Venice-Italy. The necessity of intervention was determined by an excessive eccentricity at the joints introduced by the builder during the assembly of the welded structure in order to achieve and eased up and cheaper procedure. With reference to the original project, the trusses were welded at an increased wheelbase, due to a greater easiness of construction of the joints characterized by a three dimensional geometry. Furthermore, during the positioning of the girders on the supports, constituted by a number of steel tripods, further problems were produced by former survey inaccuracies, that led to the creation of additional eccentricities between the joints and the supports on the tripod.

The situation that was determined by the mentioned factors was analyzed by the implementation of 3D global and local finite element models that demonstrated a non-allowable state of stress within the structure under certain load conditions.

In order to understand the minimum action able to bring back the structure to an adequate condition, a number of consideration explained in the following were carried out.