Uncertainty Analysis of Reinforced Concrete Masonry Walls under Out-of-plane Loading

Abstract

Masonry, as a conventional construction material, is widely used due to its durability, strength, hygrothermal performance, and aesthetics. However, the behaviour of masonry structures is not fully comprehended, especially in the face of uncertainty. This lack of understating on the behaviour of masonry structures is usually compensated by imposing overly conservative design provisions. Inherent uncertainties in the material and geometric properties of masonry structures result in large scatter in the experimentally or analytically predicted behaviour. Thus, understanding the influence of these uncertainties on the structural behaviour of masonry structures is of paramount importance to lay down the basis for reliable structural design. This thesis focuses on the uncertainty analysis of the out-of-plane behaviour of reinforced concrete masonry walls using mechanics-based finite element (FE) models and experimental testing data. Specifically, this thesis includes three main phases. In the first phase, the probabilistic behaviour of reinforced concrete masonry walls is investigated, employing mechanics-based macro FE models in conjunction with Monte Carlo simulations (MCS). The effect of the inherited uncertainties in the material and geometric properties on different response quantities (e.g., load capacity and deformation capacity) is also investigated through a variance-based global sensitivity analysis. Additionally, the model uncertainty in FE-predicted load capacity is quantified to characterize the model error, which is found to be influential compared to geometric and material uncertainties, though FE models are commonly used for numerical studies. The second phase focuses on assessing the reliability of reinforced concrete masonry walls loaded out-of-plane with the limit state functions formulated employing the developed macro FE models. In this phase, the importance of model uncertainty on the reliability assessment is revealed. The reliability assessment conducted considering different global and local failure criteria provides iv insights into their effect on the safety levels of walls. The reliability assessment is found to be sensitive to the adopted failure criteria. In addition, different factors are found to influence the reliability assessment of the walls designed according to the masonry design code; specifically, walls with different slenderness ratios and load eccentricities show inconsistent reliability levels. The model errors associated with the out-of-plane load capacity provided in masonry design codes in North America (i.e., CSA S304-14 and TMS 402-16) are investigated in the third phase. FEbased and experimental data are used to quantify the model error associated with design codebased models. In addition, the sensitivity of the model error to the variations associated with different design parameters is investigated. It is found that CSA S304-14 is overly conservative for highly slender walls with low load eccentricities, while TMS 402-16 gives more reasonable capacity predictions for such walls. However, TMS 402-16 is found to overestimate the capacities of highly slender walls with relatively high reinforcement ratios and load eccentricities. The codebased models are employed in reliability assessment to investigate the influence of the accuracy of the behavioural model on the reliability of the masonry walls. It is found that using the codebased models in the reliability assessment without considering their model error results in significantly biased reliability results. This highlights the need and potential room for design code model improvement.