Bridge Design

2Bridge Design: Site Data and Basic Conditions

2.1 Design Phases and Methodology

The design of a bridge should be developed in a sequence of phases that are relevant for selection between several design options. Joint decisions by designer and owner should be taken along all design phases.

Input data for design is needed. Hence, a data acquisition process is required, namely, for topographic surveys, geological, hydraulic data and environmental issues. The acquisition process requires preliminary concepts about bridge design options. This is the case for geotechnical investigations at the location of bridge piers, requiring, for example, the development of geological surveys at two design phases – one at the preliminary design phase and a second one after a decision about the retained option.

Design practice varies from country to country but, in short, the following design phases may be considered: preliminary design, base case design and the final/execution design.

The designer should start by fixing the conditions to develop the design options, namely the possible locations for the bridge (if it is not fixed in the contract documents), vertical and horizontal clearances, typical width for the deck (from the number of lanes and width of the walkways to be accommodated) and basic design criteria (design codes) to be adopted.

The preliminary design is the key phase for the success of a bridge design. The most important design options are investigated and proposed to the owner. ...