Slab Frame Bridges Structural Optimization Considering Investment Cost and Environmental Impacts

University dissertation from Stockholm : KTH Royal Institute of Technology

Abstract: This research encompasses the automated design and structural optimization of reinforced concrete slab frame bridges, considering investment costs and environmental impacts. The most important feature of this work is that it focusses on realistic and complete models of slab frame bridges rather than on optimization of only individual members or sections of a bridge. The thesis consists of an extended summary of publications and three appended papers. In the first paper, using simple assumptions, the possibility of applying cost-optimization to the structural design of slab frame bridges was investigated. The results of the optimization of an existing constructed bridge showed the potential to reduce the investment cost of slab frame bridges. The procedure was further developed in the second paper. In this paper, automated design was integrated to a more refined cost-optimization methodology based on more detailed assumptions and including extra constructability factors. This procedure was then applied to a bridge under design, before its construction. From the point of view of sustainability, bridge design should not only consider criteria such as cost but also environmental performance. The third paper thus integrated life cycle assessment (LCA) with the design optimization procedure to perform environmental impact optimization of the same case study bridge as in the second paper. The results of investment cost and environmental impact optimization were then compared. The obtained results presented in the appended papers highlight the successful application of optimization techniques to the structural design of reinforced concrete slab frame bridges. Moreover, the results indicate that a multi-objective optimization that simultaneously considers both environmental impacts and investment cost is necessary in order to generate more sustainable designs. The presented methodology has been applied to the design process for a time-effective, sustainable, and optimal design of concrete slab frame bridges.