Fibre-reinforced polymers (FRPs) are a promising corrosion-resistant alternative to steel reinforcement. FRPs are, however, generally costly and have a high energy demand during production. The question arises whether the high performance of FRPs and possible savings in concrete mass can counterbalance initial costs and environmental impact. In this paper, a parametric design study that considers a broad range of concrete infrastructure, namely a rail platform barrier, a retaining wall and a bridge, is conducted to assess the mass-related global warming potential and material costs. Design equations are parametrised to derive optimum reinforced concrete cross-sectional designs that fulfil the stated requirements for the serviceability limit state and ultimate limit state. Conventional steel reinforcement, glass and carbon FRP reinforcement options are evaluated. It is observed that the cross-sectional design has a significant influence on the environmental impact and cost, with local extrema for both categories determinable when the respective values become a minimum. When comparing the cradle-to-gate impact of the different materials, the fibre-reinforced polymer-reinforced structures are found to provide roughly equivalent or, in some cases, slightly more sustainable solutions than steel-reinforced structures in terms of the global warming potential, but the material costs are higher. In general, the size of the structure determines the cost competitiveness and sustainability of the FRP-reinforced concrete options with the rail platform barrier application showing the greatest potential.
<p>Nowadays large box-girder concrete bridges are either built using pre-cast segmental erection or in-situ casting of concrete. Using these methods sets limitations when it comes to construction speed or to segment length due to the weight of full-cast concrete segments. To close the gap between the two construction approaches, the Institute of Structural Engineering of the TU Wien has developed new technologies for bridge construction using thin-walled pre-fabricated elements originally used in building construction. Based on these developments, an innovative construction method has been proposed, which consists of the following steps:</p>
<ul>
<li>Highly automated production of thin-walled concrete elements in a pre-casting-plant</li>
<li>On-site production of box-girder segments using thin-walled elements</li>
<li>Connection of the segments with post-tensioning tendons to form a bridge girder</li>
<li>Installation of the girder to its final position using any construction method as for example incremental launching or the balanced lift method</li>
<li>Pumping of in-situ concrete, to complete the girder in the final position</li>
</ul>
<p>The presented research shows, that this approach is advantageous for construction methods, with large differences in bending moment distribution during the construction stages and the final state. The required amount of materials cannot only be reduced, but the construction process can be accelerated as well, therefore improving the efficiency in bridge construction. Results of tests on large-scale specimens, which will be described in detail, show the potential of the new method.</p>
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