In Europe, including the Netherlands, a significant Replacement and Renovation (R&R) challenge is expected between 2040 and 2060 for concrete bridges and viaducts due to ageing infrastructure reaching their end of service-life. Various options emerge when existing structures fail to meet current requirements, including accepting additional risk without mitigation measures, making minimal adjustments for a short period, or implementing longer-term modifications. Existing frameworks for assessing R&R decisions, include technical and cost aspects, although lack of sustainability criteria and performance prediction.

The research objective is to develop a decision-making framework for evaluating different strengthening methods versus replacement, considering factors such as (environmental) cost, service-life, structural performance prediction and reliability. The research includes a comparison method on different strengthening methods, external prestressing (EP), memory-steel (MS), carbon fibre reinforced polymer (CFRP) and ultra-high performance concrete (UHPC), versus total replacement. The study mainly focuses on shear deficiencies and strengthening for shear in precast pre-stressed T-beam bridges.

The research starts with a literature review on decision frameworks, structural deterioration mechanisms, T-beam assessment and strengthening methods. The literature review defines and elaborates on key performance indicators relevant to the study. The First Order Reliability Method (FORM) is used to determine failure probabilities by comparing demand versus capacity, providing insights into the current condition and expected lifespan of the structure. A multi-objective optimisation process is introduced to determine the most effective strengthening method based on the desired service-life extension. The goal of this optimisation process is to minimise (environmental) costs while maximising strength, subject to fabrication and physical constraints. A multi-criteria decision-making approach is applied, using the Analytical Hierarchy Process (AHP) to support complex decision-making where multiple variables and criteria must be prioritised. A parametric study is conducted to explore how (geometric) parameters influence decision outcomes.

The parametric framework enables the decision for optimal strengthening to be run multiple times, allowing trends and patterns to appear. Within the analysis, when accounting for varying spans, cross-sections, different states of current reliability and distinct deterioration phenomena for each strengthening method, CFRP consistently proves to be the best-performing and most frequently chosen option. This is due to its high strength-to-weight ratio, which helps minimise material costs and environmental impact. External prestressing excels mainly for larger spans and applying memory-steel is very unfavourable in any case when compared to other strengthening methods. Replacement ranks high in many cases but requires careful consideration, as the design is not fully optimised to each case and impact assessment remains less developed.

For complex geometries, the decision-making framework become less reliable, because strengthening and reliability calculations grow significantly more complex, which is not accounted for. A more integrated approach, considering the interaction between bending and shear, would improve the strengthening designs and could be further refined. Ultimately, while the framework provides a structured approach to decision-making, it should be seen rather as a supporting tool than a stand-alone decision-maker.

This research addresses how Ricanau Mofo, a low-lying village in Surinam, can become a more water-adaptive and sustainable village, while it faces land erosion, river bank erosion, changing rainfall patterns and sea level rise. It is urgent to intervene, as these issues are expected to increase in occurrence due to climate change. Constraints and limitations that are important to take into account are cultural preservation, maintaining accessibility to the Cottica River, the limited availability of financial resources and the need for a low-maintenance intervention.

Three strategies are proposed. The first focuses on addressing land erosion. Planting vegetation on critically eroding areas is a short term measure, while the long-term involves constructing footpaths with drainage channels. This not only mitigates soil erosion, but also regulates water and is relatively cost efficient. The second strategy targets the river bank erosion, which includes wooden bulkheads with vegetation and stones for short term implementation. For the long term, a river bank protection system with groynes is designed, to break waves, slow down the stream velocity and in time causes land gain. As the long term plans require external financial aid, a business case is set up and shared with the captain of Ricanau Mofo, STEORR, the District Commissioner and the Ministry of Public Works. The third strategy addresses water damage in the urban environment. Short-term it consists of providing building guidelines of where to build more water adaptive, and how. This is placed on an informational board in the village. The long-term contains a flood early warning system and recommended equipment.

This project's significance lies in identifying interventions that are effective against erosion and water damage while being locally implementable in the rural areas of Surinam. It can be seen as a pilot project that is scalable to other villages along the Cottica River or in the whole of Surinam. However, there are limitations to the project. The most important is the lack of data quantity and data quality. This caused implications for dimensioning the interventions and their financial impact. Another limitation is that the project does not create ‘dry feet’ for the village; it creates a way of mitigating water damage while living next to the Cottica River. In addition, there is a limitation in the financing of follow-up projects. Therefore, a business case is also being delivered to the Ministry of Public Works, the District Commissioner of Marowijne South-West and the captain of Ricanau Mofo. They can use it to apply for funds from international organisations and include it in future policy plans.

To summarise, Ricanau Mofo can become more water adaptive by regulating how to build and where, by continuing the prototype of the bulkheads by planting more vegetation and, by requesting financial aid for the river bank protection long term. As Figure 0.2 shows, it not only contributes as a report, but also in a tangible form of a prototype and in educational information boards in the local language to enhance the continuity and help the village.