Mechanical and Mechatronics Engineering

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This is the collection for the University of Waterloo's Department of Mechanical and Mechatronics Engineering.

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Browsing Mechanical and Mechatronics Engineering by Author "Al-Mayah, Adil"

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    Development, Optimization and Testing of an Innovative Wedge Anchorage for CFRP Plates
    (University of Waterloo, 2018-12-14) Alhusain, Mustafa; Al-Mayah, Adil
    Replacing degraded concrete structures can be quite expensive and time consuming; thus, strengthening these structures with fiber reinforced polymer (FRP) elements, such as carbon FRP (CFRP) plates, is more practical. Prestressing FRP elements is one of the most economical used solution due to its effect on utilizing the high strength of the FRP materials while improving the performance of structural elements. In order to prestress the FRP component, gripping using anchorages must be provided at both ends. However, anchoring FRP plate is challenging due to its vulnerability to lateral loading; therefore, specially designed anchorage systems are required to grip FRP plates effectively to avoid any premature failure. The presented work investigates the development and optimization of an innovative anchorage that is reliable, reusable, compact and light in weight for gripping CFRP plates. To fulfil these requirements, a wedge anchorage system is chosen as the most suitable for gripping CFRP plates Material selection process is conducted to select the optimal materials for the sleeves, the wedges and the barrel of the anchorage. An FEM model of the wedge anchorage is developed using ABAQUS finite element package. An optimization process is performed to find the optimal dimensions of the anchorage through which the anchoring strength and the reusability of the anchorage are improved. The effect of the presetting distance on the performance of the optimized anchorage is investigated. Several failure theories are used to investigate the likelihood of CFRP premature failure. Two new analytical models are developed to verify the accuracy of the FEM model. The results of the analytical models are compared well to the FEM results. The optimized wedge anchorage is then manufactured and experimentally tested. Eight tensile tests are performed to evaluate the performance of the optimized anchorage by gripping the sides of the CFRP plates using the optimized anchorage and a larger dead-end anchorage. Five tests are performed by presetting the optimized anchorage using presetting rig, two of which use hard copper sleeves. The other three tests are conducted by hammering the optimized anchorage. The dead-end is presetted in every test to avoid CFRP slipping. The optimized anchorage system is capable to carry the guaranteed ultimate tensile strength of the CFRP plate when soft sleeves are used. The effect of presetting distance on the CFRP slipping is investigated. Damage analysis is performed after conducting eight tensile tests to examine the reusability of the optimized wedge anchorage.
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    Three-Dimensional CT Imaging and Microstructural Mechanical Modeling of Corrosion and Freeze-Thaw Damage of Concrete
    (University of Waterloo, 2022-10-17) Alhusain, Mustafa; Al-Mayah, Adil
    Corrosion and freeze-thaw can cause detrimental damage to concrete structures. Understanding concrete damage mechanisms at the micro-level can play an essential role in implementing effective preventive measures and efficient repair methods. Among various non-destructive testing technologies, high-resolution micro-computed tomography (µCT) imaging has been gaining popularity due to its ability to provide three-dimensional (3D) reconstructions of concrete’s internal structure and analyze its damage mechanisms. Despite its unique capabilities, the full potential of using CT imaging to investigate the general microscale damage of concrete has yet to be realized. Also, limited research has been conducted to investigate the 3D microstructural concrete damage caused by corrosion and freeze-thaw conditions. Therefore, the main objective of this research is to attain a better understanding of the effects of concrete composition and surrounding environments on the severity and mechanisms of corrosion and freeze-thaw damage. This objective was complimented by integrating mechanical characterization using CT imaging into image-based microstructural finite element (FE) modeling. Furthermore, the full potential of CT imaging was examined by investigating the accuracy of corrosion detection using an unprecedentedly large naturally corroded concrete element. The effects of mixture proportions on the mechanisms of corrosion and freeze-thaw damage were examined by investigating internal structures of concrete, such as pore characteristics. The specimens were imaged before being subjected to corrosion and freeze-thaw conditions to determine the impact of concrete composition on its pore properties, after which the corrosion specimens were exposed to 120 wet-dry cycles in salt water with a concentration of 3.5%, whereas the freeze-thaw samples were subjected to 40 cycles. The pore properties were analyzed before and after testing, and the concrete damage mechanisms were investigated. Also, the full potential of CT imaging was examined by investigating the corrosion of a 50-year-old naturally corroded concrete element that is 12 cm wide, 6 cm thick, and 17 cm high. The detected corrosion products were compared to the corrosion of the actual concrete specimen to investigate the accuracy of corrosion detection. A method for improving corrosion detection accuracy was proposed and tested. Moreover, the damage mechanisms were determined by analyzing the pore structure of the concrete element. The effects of the surrounding environment on the severity and mechanisms of freeze-thaw damage were investigated by subjecting concrete specimens of the same composition to 80 freeze-thaw cycles in distinct sulfate environments with different concentrations. The mass loss data and pore characteristics, including porosity, pore size, and pore accessibility, were analyzed throughout the applied cycles to determine the impact of the sulfate salt and concentration on the severity of frost damage. On the other hand, freeze-thaw damage mechanisms under the different sulfate environments were investigated using 3D reconstructions of concrete’s pore microstructure. Also, novel image-based microstructural FE models were developed to investigate concrete damage under corrosion and freeze-thaw conditions. Three-dimensional reconstructions of the FE elements, including the aggregates, air pores, and cement mortar, were created by thresholding and stacking the CT images. The corrosion FE model was modeled by subjecting the steel reinforcement to experiment-based uniform corrosion. On the other hand, the freeze-thaw FE models were simulated by filling the air pores with freezing water and applying the temperatures of the actual freeze-thaw cycles. The interaction between the different elements was examined by studying the internal stress distribution throughout the applied corrosion and freeze-thaw conditions. Also, the accuracy of the FE models was investigated by comparing the severity and mechanisms of the FE models to the CT data of the actual concrete specimens.