Assignment

Feasibility Project:
defininition and comparison of alternatives, design analysis of the selected solution

Description

Becca Bridge lies in the province of Pavia at the confluence of the Rivers Po and Ticino and was constructed in 1912 to make the connection between the Oltrepò and the rest of Lombardy more stable and no longer subject to the conditions of the two rivers. It is now an essential element in the landscape and the identity of the place, collective memory and the feeling of belonging of the people who live there.
After more than 100 years since its construction, however, the existing bridge is no longer able to fully perform its connection function. It was designed for traffic different from current traffic, for both volume and types of vehicles – speed and axle loads, and now severe limitations on transit are impose – there is a ban on heavy vehicles, except for Public Transport and emergency vehicles, and a speed limit of 50 kph with accesses for light vehicles.
As a result of this situation and the solicitation of the area, Lombardy Region started the procedure for the creation of a new bridge with a tender for the drafting of the Feasibility Document, divided into two stages – defining and comparing the alternatives and the design analysis of the preferable solution.

The project was developed so that a 360° view of both the work and its context was allowed and maintained, conceived individually and together as interdependent systems and not simply the result of the sum of separate elements.

Thus, the definition of the aims of technical and economic efficiency, hydraulic safety, environmental protection (for both the natural habitat and human habitat) and the common property (including the landscape and memory) were intersected with the opportunities and recognised restrictions through the analysis of the various subsystems involved (mobility, hydraulic context, natural environment and that affected by human activity, geology, and construction techniques, to name the main ones) understood to be components of a single complex system. This originated a series of alternative designs, mainly differing in the localisation and architectural-structural solution proposed for the new bridge.

The alternative designs, like the proposal of converting the existing bridge to a different use, were presented to the main institutional stakeholders. The feedback stimulated a further widening of the overall view of the project and contributed to the refinement of the design proposals that were then subjected to a rigorous evaluation and comparison stage.

The desire to guarantee extensive assessment which considered both the aspects more easy to quantify economically and the sustainability, environmental and social aspects as well as the economic one and with reference to the whole useful life cycle led to the development of a comparison method based on Cost-Benefit Analysis, carried out for each alternative, combined with a Multi-Criteria Analysis set up on the EnvisionTM and Life Cycle Assessment rating systems.

The result was a clear, comparable indication of the features, not only in terms of economic efficiency but also the overall performance of the individual alternatives which enabled a rapid evaluation of the preferable solution to subject to design analysis.