To achieve sustainability goals, the Dutch government is striving toward a circular economy, which necessitates changes in the building and construction sector—responsible for 34% of global carbon dioxide emissions in 2022. Steel production contributes significantly, accounting for 7.2% of global greenhouse gas emissions. Reuse, a key strategy within the circular economy, holds great potential but remains underutilized in infrastructure projects. This research investigates the feasibility and environmental impact of reusing a Rijkswaterstaat bridge, addressing the central question: What are the feasibility and environmental implications of reusing the Keizersveerbrug, a steel truss bridge, on an object-level basis, as assessed through a comprehensive case study design process?

A donor structure file, following the technical guideline NTA 8713 for the reuse of steel elements, is developed to assess the feasibility of reusing the Keizersveerbrug. A visual inspection confirms that the bridge is in good condition, with minimal corrosion and damage. The truss bridge aligns well with the design criteria of the new application, allowing for multiple feasible design options for both the approach ramps and the main span. An evaluation based on environmental impact, user comfort, and integration into the surroundings leads to a preliminary design. This design incorporates three 100-meter truss bridge elements from the donor structure, with adaptations including a new deck and a fresh paint layer.

An environmental impact assessment, conducted using Environmental Product Declarations and in accordance with NEN-EN 15804+A2, demonstrates significant environmental cost savings. When considering all life cycle stages, a reduction of 0–66% is observed, while excluding life cycle stage D results in a 25–60% reduction compared to variants constructed from other materials. Additionally, this research adapts the traditional design cycle to integrate reuse considerations, providing a structured approach for engineers addressing the challenges of reusing steel bridges. These findings underscore the potential of reuse to contribute to sustainable infrastructure that aligns with the principles of a circular economy.

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Playa Unión and Puerto Rawson are facing severe coastal erosion and increasingly the negative effects. Since the first half of the 20th century there have been signs of erosion, but also of sedimentation. However, the coastline in the project area is retreating over the years. The situation has recently been declared an emergency. Furthermore, there are several expansion plans for the port consisting of new quay walls and dredging. It is unsure if these plans will influence the erosion. In this report, the following research question is formed: ”What are valued, preferably nature-based, interventions that can mitigate the coastal erosion in Playa Unión and Puerto Rawson considering the planned expansion of the port?” Due to the limited information and data available, assumptions have been made during the research. A site analysis and a CoastSat analysis are conducted to research the morphology of the coastline and its drivers. The coast has been shaped into a steep upper section of coarse granular material and a gentle lower slope with finer material. The main driver of longshore sediment transport in the area are swell waves, with predominant directions SSE and E. This transport is directed from south to north, resulting in the inflow and outflow of sediments. Furthermore, there is a sediment flow from the Chubut river. Due to the construction of the port’s breakwaters, the longshore sediment transport is interrupted, which causes an imbalance in the sediment flow in the system. More sediment flows out of the system than enters, causing coastal erosion. The development of the port contains public as well as private expansion plans and maintenance dredging. The expansion plans will have little effect on its surroundings. The private plan include a parallel breakwater, which alters the natural balance in the area and dredging works, for which the stability of the existing breakwaters has to be figured out. A stakeholder analysis was done to get insights in the opinions and visions of the stakeholders. This was done by interviewing stakeholders and by doing a questionnaire, resulting in a power-interest grid and overview of interests and attitudes. The boundary conditions for the interventions and criteria for the multi-criteria analysis are partly formulated as a result of the stakeholder analysis. The following interventions were considered in this report: • Permeable pile groynes and low crested groynes
• Opening the northern breakwater: opening and reshaping with a curve, constructing tunnels underneath the breakwater and a sediment bypass
• Port expansion and a sediment bypass with power supply southern of the port
• Dredging and moving sediment
• Sediment trap
• Plant vegetation with beach nourishment
• Gravel engine
• Temporary longitudinal flood barrier as a short term intervention.
A conceptual multi-criteria analysis in combination with a nature-based assessment has been conducted to distinguish the most promising interventions in the conceptual design phase. The criteria formulated were effectiveness, easiness of implementation, maintenance, environmental impact and the benefits for recreation. From this, it can be concluded that the gravel engine and the plant vegetation with beach nourishment score the best.
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