Load capacity assessment of concrete dams often includes verification of the stability for multiple separate failure modes, such as sliding and overturning. However, in the case of dams, the underlying failure mechanism for these failure modes may be too idealized, and the analysis could yield inaccurate results. Previous research has, for example, shown that regular rigid-body sliding failure analysis provides inaccurate load capacity estimates for dams with uneven interface geometries. This article discusses the behavior of such dams and presents a failure mode that combines the traditional sliding and overturning failures. The failure mode is termed combined sliding and overturning and serves as an intermediate to the traditional failure modes. It allows for the assessment of concrete dams with uneven interface geometries, whose behavior is not expected to be fully represented by only sliding or overturning. To estimate the load capacity for the presented failure mode, an analytical formulation based on simple force and moment equilibrium is provided. The formulation is compared with finite element simulations and previously reported results from experimental scale model tests and is shown to accurately predict the load capacity.

Concrete dams are vital to society, providing storage of byproducts from mining operations, flood control, water storage for irrigation, hydropower generation, and more. However, these crucial components of infrastructure are aging, as the construction of new large dams worldwide peaked in the late 1970s. Combined with the expected impact of climate change, where extreme weather events are predicted to occur more frequently, ageing dams are becoming an increasing concern due to the associated risk of structural failure.

Given the potentially severe consequences of dam failure, ensuring operational safety typically involves regular maintenance, monitoring, and structural analysis. Focusing on structural analysis, various national design codes and guidelines exist, most of which prescribe deterministic analyses based on predefined failure modes. However, these failure modes are idealized, and research suggests that their use tends to produce inaccurate and conservative load capacity estimates for concrete dams. Considering the significant risk and the economic and natural capital invested in dams, it is essential to obtain accurate estimates of load capacity to maximize service life and prevent unnecessary strengthening measures.

This thesis explores and proposes alternative approaches for more accurate evaluation of concrete dam load capacity and safety. A new failure mode, referred to as combined sliding and overturning, which merges two common failure modes from current practice, is introduced. By simultaneously considering these opposing mechanisms, the failure mode accounts for the beneficial effects of foundation surface irregularities in analytical assessments. Both the failure mode and the load capacity obtained from the corresponding analytical formulation are confirmed by finite element analyses (FEA) and physical scale model tests.

The novel analytical formulation and FEA are applied in conjunction with reliability analysis methods, including the first-order reliability method (FORM) and metamodeling, providing accessible alternatives to the current deterministic approach. By offering insight into the reliability of the Swedish concrete dam population and the sensitivities of key parameters, these reliability analyses form a basis for more informed decision-making regarding operational safety and strengthening measures. By incorporating alternative approaches, the shortcomings of current assessment practices can be addressed, helping to reduce the commonly perceived conservatism in current load capacity evaluations.

When assessing the sliding stability of a concrete dam, the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by current dam assessment guidelines. However, these asperities can potentially improve the load capacity of a concrete dam in terms of sliding stability. Although their influence in a sliding plane has been thoroughly studied for direct shear, their influence under eccentric loading, as in the case of dams, is unknown. This paper presents the results of a parametric study that used finite element analysis (FEA) to investigate the influence of large-scale asperities on the load capacity of small buttress dams. By varying the inclination and location of an asperity located in the concrete-rock interface along with the strength of the rock foundation material, transitions between different failure modes and correlations between the load capacity and the varied parameters were observed. The results indicated that the inclination of the asperity had a significant impact on the failure mode. When the inclination was 30° and greater, interlocking occurred between the dam and foundation and the governing failure modes were either rupture of the dam body or asperity. When the asperity inclination was significant enough to provide interlocking, the load capacity of the dam was impacted by the strength of the rock in the foundation through influencing the load capacity of the asperity. The location of the asperity along the concrete-rock interface did not affect the failure mode, except for when the asperity was located at the toe of the dam, but had an influence on the load capacity when the failure occurred by rupture of the buttress or by sliding. By accounting for a single large-scale asperity in the concrete-rock interface of the analysed dam, a horizontal load capacity increase of 30%–160% was obtained, depending on the inclination and location of the asperity and the strength of the foundation material.

Dams are vital infrastructure for society as they provide various services (e.g., flood prevention, storage of byproducts from mining operations, water storage for irrigation and hydropower generation) by the impoundment of liquids. However, the storage of considerable volumes of liquids introduces a risk of uncontrolled discharge, due to dam failure, which could result in catastrophic outcomes. Consequently, the safety must be ensured throughout a dam’s service life and thus regular assessments are required.

For concrete dams, the current practices of stability assessment methods found in guidelines and regulatory rules require idealizations. This need for idealization is a weakness of current assessment methods as elucidated by the appended scientific articles. The essence of the results of the appended articles demonstrates that certain parameters and features of a dam, which are commonly neglected in current dam assessment, significantly influences the load capacity of a dam. Therefore, this study primarily deals with alternative assessment methods that can be used for dams.

Therefore, as an outcome of an extensive literature review on probabilistic analysis and scale model testing, summarized in the chapters of the thesis, a framework for concrete dam assessment is proposed. Even though the methods can be individually employed to assess the stability and safety of a dam, an approach that integrates the strengths of each method is currently not available.

The proposed framework is novel and combines scale model testing, finite element analysis, probabilistic analysis and is intended to resolve issues identified with current assessment methods. The framework integrates the strengths of each method provides a robust assessment strategy where cross-validation of the failure mode and capacity is achieved by utilizing both finite element analysis and scale model testing. Furthermore, in contrast to current dam assessment methods, it allows for large geometrical variations in the rock-concrete interface to be included in the analysis, which contributes significantly to the capacity of a concrete dam as elucidated by the appended articles.

The work in this thesis presents the theoretical foundation of the framework. It is intended to be applied in a future case study to evaluate its performance on an existing buttress dam.

Over the last decades, economic growth and sustained development have enforced the need to ensure reliable and long-lasting infrastructure network to guarantee serviceability and safety. Nevertheless, detrimental effects can lead over time to insufficient structural performance under increasing service loadings and extreme events. Hence, Structural Health Monitoring (SHM) arises as a solution to cope with the need of having timely and continuous data to assess the state of crucial structural assets, such as prestressed concrete bridges. On this matter, the validation of the retrieved data becomes essential for the risk-based decision making in the assessment of bridges, where selecting the most suitable monitoring system could allow to addressed main causes to the right phenomena of deterioration during the service life of the bridge. Consistently with these efforts, this paper deals with a comparative study between the data acquired by different strain-based sensors such as Fiber optic systems (FOS) and strain gauges that were installed to monitor a proof loading test developed on a 65-year-old balanced cantilever prestressed concrete bridge located in Northern Sweden. The monitored data led to establish main differences between emerging types of monitoring systems such as FOS to the well-based strain gauges when exposed to low temperature conditions. Conclusions regarding the influencing parameters between both retrieved data are drawn when evaluating the structural response under serviceability loading conditions is performed, supporting decision makers when different levels of structural assessment are required.

Common analytical assessment methods for concrete dams are unlikely to predict material fracture in the dam body because of the assumption of rigid body behavior and uniform- or linear stress distribution along a predetermined failure surface. Hence, probabilistic non-linear finite element analysis, calibrated from scale model tests, was implemented in this study to investigate the impact of concrete material parameters (modulus of elasticity, tensile strength, compressive strength, fracture energy) on the ultimate capacity of scaled model dams. The investigated dam section has two types of large asperities, located near the downstream and/or upstream end of the rock–concrete interface. These large-scale asperities significantly increased the interface roughness. Post-processing of the numerical simulations showed interlocking between the buttress and the downstream asperity leading to fracture of the buttress with the capacity being determined mainly by the tensile strength of the buttress material. The capacity of a model with an asperity near the upstream side, with lower inclination, was less dependent on the material parameters of the buttress as failure occurred by sliding along the interface, even with inferior material parameters. Results of this study show that material parameters of the concrete in a dam body can govern the load capacity of the dam granted that significant geometrical variations in the rock–concrete interface exists. The material parameters of the dam body and their impact on the capacity with respect to the failure mechanism that developed for some of the studied models are not commonly considered to be decisive for the load capacity. Also, no analytical assessment method for this type of failure exists. This implies that common assessment methods may misjudge the capacity and important parameters for certain failure types that may develop in dams.

For concrete dams founded on rock, there are only a few options in the common analysis methods to account for large‐scale asperities. However, previous research alludes that they have a significant impact on the behaviour of interfaces under shear. This study investigates the behaviour of concrete dam scale models with varying interface geometries, under a realistic set of eccentric loads. The outcome of the scale model tests shows that not only the capacity of the scale models was significantly impacted by the asperities, but also the type of failure in the scale models.

The enhanced carbon footprint of the construction sector has created the need for CO₂ emission control and mitigation. CO₂ emissions in the construction sector are influenced by a variety of factors, including raw material preparation, cement production, and, most notably, the construction process. Thus, using biobased constituents in cement could reduce CO₂ emissions. However, biobased constituents can degrade and have a negative impact on cement performance. Recently, carbonised biomass known as biochar has been found to be an effective partial replacement for cement. Various studies have reported improved mechanical strength and thermal properties with the inclusion of biochar in concrete. To comprehend the properties of biochar-added cementitious materials, the properties of biochar and their effect on concrete need to be examined. This review provides a critical examination of the mechanical and thermal properties of biochar and biochar-added cementitious materials. The study also covers biochar’s life cycle assessment and economic benefits. Overall, the purpose of this review article is to provide a means for researchers in the relevant field to gain a deeper understanding of the innate properties of biochar imparted into biochar-added cementitious materials for property enhancement and reduction of CO₂ emissions.

Analytical methods of structural stability assessment of concrete dams are often too simple and thus conservative in their predictions.Without the actual foundation geometry, capacity for some rigid body failure modes are underestimated. This is problematic when decidingupon remediation activities of a dam that is considered unstable and may divert the restoration activities from where they are mostimpactful. In a previous study by Sas et al. 2019 where a section of an existing dam was scaled down and tested experimentally, the modelindicated that several areas were experiencing large stresses, potentially leading to failure. This raised the research question whetheranother type of failure would occur for different material properties. Therefore, this paper delves into a probabilistic numerical approach,through finite element analysis, to evaluate dam stability based on randomization of a number of material properties such as modulus ofelasticity, tensile strength, compressive strength, and fracture energy. The variation of the aforementioned material properties did notimpact the failure mode, which was consistent among a broad range of material strengths.