Selection of Sustainable Short-Span Bridge Design in Brazil

Owing to the elevated cost of bridges, especially when compared to the cost of roads, their rational design and material selection are fundamental properties to consider when aiming to reduce the environmental impacts and lengthen the lifespan of the bridge. Especially in developing countries, the construction of new bridges (mainly short spanned) is still a necessity, and it is important that these new structures are designed according to all the sustainability parameters, instead of being based only on the construction cost. Thus, the present work aims to study short-span bridges by integrating environmental assessments into the decision-making process. To achieve this goal, three short-span bridge designs, proposed by public organizations in Brazil, are evaluated: Precast concrete bridge, mixed concrete/steel bridge, and timber bridge. In order to allow comparison, the same location and span are considered. The structures are evaluated considering the following quantitative aspects: Cost of construction, assembly and material transportation, lifespan, and environmental impact (measured by the global warming potential, GWP). In addition, some more subjective factors are considered, such as the architecture (layout and appearance) and the user’s sensation of security. The selection is made by the adoption of two multi-criteria decision-making methods (analytic hierarchy process or AHP and Vikor). The results obtained with both methods indicate the mixed concrete/steel bridge as the most adequate alternative. Some additional analysis is performed in order to evaluate the influence of the qualitative aspects, as well as to study the importance of the variations in the costs on the results.