INVESTIGATION OF SHEAR CONNECTION SYSTEMS FOR PARTIALLY COMPOSITE INSULATED CONCRETE AND DOUBLE WYTHE CAVITY MASONRY WALLS
Creators: Egbon, Benedict N.
Publisher: name: University of Alberta Library
Year: 2024

<p>Insulated concrete and double wythe cavity masonry walls are commonly used on building exteriors. Both wall types consist of inner and outer layers known as wythes, which surround an insulation layer, and these wythes are joined by mechanical devices known as shear connectors. In insulated concrete walls the inner and outer wythes are made entirely of concrete while that of double wythe cavity masonry walls are mostly made of bricks and Concrete Masonry Units, respectively. Overall, the structural performance of both walls is largely influenced by the shear connection system, and existing shear connection systems are currently being challenged by larger insulation thicknesses needed to meet stricter energy requirements. At the core of these changes to the thermal requirement for building envelopes, the structural load on walls such as the dead and live load are relatively unchanged, which means innovative considerations on how the load is transferred through the walls must be made. These innovative considerations, such as new shear connection mechanisms often create additional composite action in walls. Experimental, finite element, and analytical approaches can be used to quantify the amount of composite action developed in the walls, but existing approaches are cumbersome or limited to only uncracked conditions. <br>
This thesis presents a study focused on increasing composite action using new shear connection mechanisms as well as developing a unified analytical model to analyze the behaviour of partially composite insulated and double wythe cavity masonry walls. While both walls are similar in composition, double wythe cavity masonry walls are not completely sandwiched due to an air gap that allows for moisture drainage. This airgap is absent in insulated concrete walls due to superior moisture resistance. This means different methods have to be developed to improve the shear connection system for both walls. Rectangular and trapezoidal notches were created in different insulation types and used along with inclined GFRP connectors to improve the shear connection strength in insulated concrete walls, while a novel inclined connector was developed at the University of Alberta for double wythe cavity masonry walls. Small-scale longitudinal shear testing was executed for both shear connection systems, and the notches increased the shear connection strength by as much as 50%, with the rectangular notch shown to be more effective due to proper locking mechanism with the insulation. Meanwhile, the inclined novel masonry connector proffered larger shear strength per connector cross-sectional area than existing traditional plate connectors, in some cases up to 212%.<br>
To compliment experimental tests, analytical expressions were developed to predict the strength of the shear connection schemes. A simplified analytical model was developed to predict the load-deflection response of both walls under flexural loading and more importantly, the amount of composite action generated by such shear connection mechanisms in full-scale walls. The analytical model was validated with experimental tests from literature, with an average test to predicted strength ratio of 0.94 with a coefficient of variation (COV) of 0.18 for insulated concrete walls. For double wythe cavity masonry walls, this ratio was 0.72 with a COV of 0.29. Among other factors examined along with the shear connection schemes in full-scale walls, the shear connector inclination and spacing influenced the degree of composite to a larger extent than others.</p>