Concrete, as the most widely used construction material, is associated with a high environmental impact. Within the present study, structural optimization is the method of choice to counter this issue. The entire process, from optimization, to design, experiments and numerical simulation is outlined. Embedded in the framework of a design competition (Concrete Girder Optimization Competition 2021), a bridge between structural engineering and mathematical optimization is demonstrated. Two design concepts for optimized concrete girders, one with internal and one with external reinforcement, yet both based on strut‐and‐tie modeling, were investigated. Within the boundaries of the competition, several conclusions can be drawn: The results indicate the importance of an adequate structural interpretation of topology optimization results to obtain satisfying structural performance. The environmental evaluation outlines that the reinforcement mass has a substantial share in the total Global Warming Potential. A successful numerical re‐simulation of selected girders can serve as a modeling base for other researchers. Compared to a conventionally designed girder an increase in resource efficiency, measured by load‐carrying capacity versus environmental impact, of more than 30% was achieved.
The potential of non-metallic reinforcement to be an environmentally sustainable alternative to classic steel reinforcement in concrete has become evident in recent years. The high-performance fibres used to produce non-metallic reinforcement elements have a considerably lower weight to transferable tensile forces ratio and are almost non-corrosive under common exposures. These indicators allow for a high environmental performance throughout the extended life cycle of the product. At the same time, substantially more resources and energy per unit weight are required for their production in some cases, e.g. for carbon fibres, compared to conventional reinforcing steel. The presented work addresses this conflict by closing a number of obvious research gaps. Despite an increasing number of publications during the last years, so far there are no comprehensive sets of data available on the environmental impact of various concrete reinforcing materials. With the data compiled in this work, for the first time, an objective comparison of different reinforcement systems (conventional and alternative) is presented that differentiates various environmental impact categories and therefore enables to perform Life Cycle Assessment (LCA). Other often observed shortcomings in sustainability assessments in concrete constructions are that an extension of the service life due to improved durability and the burden a material poses at the end of its life cycle are not considered. Comprehensive reviews of durability considerations help to develop an estimation of the service life. In addition, a state-of-the-art on possible strategies for dismantling, recycling and reuse of alternative non-metallic reinforcement systems shows that the composition of the FRPs, i.e., fibre and matrix materials, not only has a strong influence on the environmental impact in the production phase, but also on the durability as well as on a possible reuse.
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