DESIGN OF BRIDGES

Description

The bridge design phase is probably the most fascinating and most difficult task for an experienced engineer if the design is original design and not industrial/repetitive work. It is unnecessary to provide the definition of the bridge design process, list the various steps required, and detail the bureaucratic procedures involved in this context. Instead, it should be stated that the bridge is a complex structure that introduces into the surrounding landscape relevant variations, dealing with a number of specialist fields: for example, hydraulic, geotechnical, landscaping, structural, architectural, economic, and sociopolitical considerations.

For this reason, before starting the design of a bridge, a concept should be developed, with the realization of a scaled model, as a simulation of the three-dimensional (3-D) overview of the construction and of all the considered alternatives. From this initial concept, some parametric considerations need to be performed to estimate the costs. This preliminary analysis is the basis for an open discussion with the client, the managing agencies, and any relevant local government agency on the most suitable solution. Only when costs and the concept are agreed upon can the design stage start: the successive steps of the preliminary, definitive, executive design, finally culminating in a construction project that entails the actual erection of the bridge.

For large-scale projects, the preliminary stage includes economic and financial studies as well. It should be known that the majority of the many variables included in the design stage are not fixed, as they depend on the precise place and time of the realization—e.g., there is not the best finite element method (FEM). Rather, the FEM software most suitable for the specific bridge design must be chosen, and the same applies to codes and standards, the amount of human resources, and the hardware instrumentation required. The most successful project is a perfect mix of these various components. Surely, a good project must include an architectural consciousness, the structural engineering knowledge, the professional experience, and a strong informatic infrastructure.