Concept Development of an Aluminum Pedestrian Bridge
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As part of new initiatives from Norwegian Public Road Administration (NPRA) and Nye Veier AS towards reduced cost of road construction and maintenance, alternative materials for bridges are being considered. For the construction phase, quick installation and utilization of prefabricated units are being requested. For the operational phase, solutions not requiring periodical maintenance are favorized. In total, these new requirements are well suited for the use of aluminum. Especially for pedestrian bridges crossing roads with heavy traffic. The primary objective of this thesis is to evaluate the potential of aluminum solutions within pedestrian bridges. This seen in competition with common steel and concrete solutions as well as new materials such as fiber reinforced polymer (FRP). The thesis contains a literature study on aluminum as construction materials and a concept development of an aluminum pedestrian bridge. This concept bridge is compared to one of two baseline solutions from NPRA. Many existing and successful aluminum pedestrian bridges demonstrates aluminum's potential in this sector. As a construction material, aluminum contains several advantages. High specific strength, high corrosion resistance, no need of periodic maintenance, low residual stresses caused by constrained thermal deformation and it is field proven bridge material. A pedestrian bridge can be designed with unique solutions by utilizing the possibilities of friction stir welding and extrusion of profiles. There is a general lack of knowledge and a historical lack of standards and guidelines for aluminum. The building sector's reliance on acquisition cost and warranty condition for their investments and not life-cycle cost analysis (LCCA) have put a limitation for aluminum pedestrian bridge projects. The initial evaluation of the bridge concept provides a 23-ton bridge structure with a fabrication cost of 6.65 MNOK. Compared to the baseline solution from NPRA the aluminum bridge only has 45% of the weight in aluminum as FRP in the baseline solution. The estimated fabrication cost ended up almost equal for the two concepts, and only the significant deviation in weight is differentiating them. Aluminum has a bright future if increased knowledge among builders and engineers, better standards and guidelines, and increased focus on LCCA becomes a reality. The development of the aluminum pedestrian bridge in this thesis demonstrates aluminum capabilities applicable for pedestrian bridges in Norway.