Influence of Foundation Rigidity on the Out-Of-Plane Flexural Response of Slender Masonry Walls
Creators: Alonso Rivers, Alan
Publisher: name: University of Alberta Library
Year: 2023

<p>Masonry walls with effective height-to-thickness (kh/t) ratios over 30 are commonly found in single-storey buildings such as school gymnasiums, warehouses, and industrial facilities.  Stringent design requirements apply for walls with kh/t &gt; 30 in North American Standards (CSA S304-14, TMS 402-16) due to the perceived vulnerability of these elements to second-order effects.  One of these requirements from CSA S304-14 consists of neglecting the stiffness provided by the foundation, regardless of the connection between the wall and the foundation, the type of foundation, or the soil type.  Although not explicitly stated in the standard, this concern is believed to be based on the potential material degradation at the wall base due to the expected rotational demand under repeated loads and the need for simplified design expressions before the availability of specialized software.  In contrast, the American masonry design standard (TMS 402-16) allows using any base condition for any height-to-thickness ratio.  This consideration leads to underestimating the wall capacity compared to the case in which the foundation rigidity is considered.<br><br>
As a result of previous studies, accounting for foundation rigidity is an untapped source of stiffness that could be used to reduce the impact of assuming a pinned base in the design of masonry walls with a height-to-thickness ratio greater than 30.  In this study, the influence of the wall-foundation interaction on the out-of-plane flexural response of tall-slender masonry walls subjected to combined axial and lateral loads is examined, aiming to propose effective height factors to be used in the design of slender masonry walls on strip footings on common soils and develop construction recommendations to improve the wall-foundation connection. <br>
To achieve this objective, experimental and numerical studies were conducted.  The experimental program consisted of two full-scale partially grouted masonry walls with a h/t of 46 that were tested under combined eccentric axial and cyclic lateral loads.  The fixity at the base varied from pinned, partially fixed, and fixed conditions, while the top was roller support during all the tests.  Data obtained from the experimental program was used to assess the influence of the rotational base stiffness on the out-of-plane response in terms of strength, stiffness, base damage, and expected failure modes.  The numerical study consisted of developing a finite element analysis model of the typical loadbearing slender masonry walls, including the static soil-foundation-structure interaction. The model was validated using the results from the experimental phase and similar studies to predict the global and local behaviour of the walls.  The validated model was used in a parametric study to create a database of the wall-foundation interaction effect on the wall response.  The database is then used to obtain the equivalent rotational base stiffness from different sizes of strip footings, foundation depths, and soil types.  The values of rotational base stiffness were used to perform stability analyses on walls with different h/t ratios to obtain elastic height factors to be used in the design of slender masonry walls.  Finally, construction recommendations were proposed to improve the behaviour of the wall-foundation connection.</p>