Researcher: Mohamed Awad
Project Duration: September 2022 – August 2023
Project Partner: Wagemaker
Research DESCRIPTION:
The inner-city quay walls of Amsterdam are approaching the end of their lifespan. In recent years, several media reported and spread the news of failure modes occurring at quay wall locations. According to recent inspection reports, approximately 200 km of quay walls have been discovered to be insufficiently technical, which either requires an immediate renewal or a lifespan extension measure. Additionally, there were events where urgent measures took place to temporarily stabilise the quay wall, such as the installation of sheet piles. It is a complex task for asset managers to deal with a densely populated area such as Amsterdam while preventing hindrances. A systematic planning process for applying intervention measures is required since using them simultaneously at all deteriorated locations is impossible. In this research, the focus lies on the retaining walls founded on wooden piles. The aim of this research is to develop a decision-making framework to decide on the most suitable intervention measure. The framework involves the option of selecting a renewal or lifespan extension measure. Therefore, the aim is to develop a framework that analyses the different types of impact caused by the intervention measures. Besides that, the failure mechanism should be checked to choose a potential intervention measure. The main research question formulated for this research is stated as follows:
“ How can the lifetime extension measure be assessed for the inner-city quay walls?”
The research method is composed of four parts to reach an interpretation of an assessment criteria in the decision-making framework. Firstly, a literature review is conducted to (1) categorise general criteria for the intervention decision of infrastructure assets, (2) identify the typical components of retaining walls in Amsterdam, (3) understand the failure mechanisms, and (4) retrieve the requirements of the municipality. The second part will collect the required data by interviewingh the six construction firms and the municipality. Each construction firm has proposed an innovative lifespan extension measure to solve the failure mode of quay walls. The interview focuses on questions related to topics such as the execution steps of the measure, structural capacity, social impact, environmental impact, and economic impact. The third part of the methodology is to develop the decision-making framework after all interviews are finalised. The framework for quay walls is linked to the general categorisation of criteria for infrastructure assets and the outcome of the interview. The framework includes seven consequent steps that need to be elaborated for each scenario study: structural capacity, safety risk matrix, economic assessment, technical feasibility, impact on the surrounding and social impact, environmental sustainability, and concluding remarks. The fourth part guides the reader to the outcome by showing the applicability of the established framework through fictive scenario studies. Three scenarios are introduced based on a given technical information, resulting in a variable outcome for each scenario.
The results of scenario study 1 show the necessity of applying a renewal option despite the lower costs of applying lifespan extension measures in comparison to renewal. The space limitation applied on the quay wall location appears to be an attention point. The required space for the potential lifespan extension measure is greater than the available space between the quay wall and residential houses. Therefore, the technical feasibility is not fulfilled by the lifespan extension measure. Scenario 2 suggests the application of lifespan extension measures. Two lifespan extension measures were proposed. However, both lifespan extensions measure scores differently in areas related to environmental, social, and economic impact. Scenario 3 recommends the application of renewal due to the severe deterioration of all quay wall components and the end of lifespan in the concise term. This placed the quay wall in the red zone of the safety risk matrix, where the renewal option is the only possibility to apply. There are certain uncertainties in this research. Research recommendations could enhance the content and applicability of the framework. Firstly, the verification of the structural capacity of the lifespan extension measure during the pilot phase is recommended. This is done by checking the predicted structural model generated in the conceptual phase with the actual structural effectiveness during the pilot phase. Secondly, the critical conditions of quay wall components have an inconsistent definition between the firms. It is currently unclear when an existing element in the quay wall falls under critical condition. This is an important input to conclude whether the lifespan extension measure is feasible by allowing drilling through the masonry wall and excavation behind the wall without damaging the entire structure. Lastly, the municipality of Amsterdam should deliver a better overview of the emission categories related to the environmental impact. Emission categories could include global warming potential, acidification, and ozone depletion. Quantitative scores of distinct toxic emission categories for the proposed lifespan extension measures could be a follow-up step of this research.