Performance-based assessment and design of squat reinforced concrete shear walls
Gulec, Cevdet Kerem
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Reinforced concrete walls with a ratio of height to length of less than two are important structural components in many commercial buildings and nearly all safety-related nuclear structures. The performance of these short (squat) walls is most important during earthquake shaking because they are designed and detailed to provide most of the lateral stiffness and strength in a building or structure. Current design provisions in codes and standards for reinforced concrete walls focus on tall (flexure-critical) walls and pay less attention to squat walls, although squat walls are far more common in practice. Squat wall failure is generally shear-related and non-ductile. Shear-critical squat walls are the focus of this dissertation. A database of information from tests of 434 squat walls is assembled with the objective of improving the current state of knowledge on squat wall response. The utility of predictive equations currently used in North America for the peak shear strength of squat walls is determined using the database. These equations do not provide unbiased estimates of peak shear strength with a small coefficient of variation. Improved empirical equations are developed for peak shear strength for rectangular walls and walls with boundary elements in a format suitable for inclusion in standards and codes of practice. Squat walls are modeled using two widely used finite element codes: ABAQUS and VecTor2. These codes are used to predict the monotonic and cyclic response of squat walls. Modeling decisions that are critical to predicting response are explored and recommendations for finite element analysis are made. Macro-level hysteretic models are prepared for a small number of squat walls for which digital load-displacement data are available. The calibrated Ibarra-Krawinkler pinching model captures well the key features of squat wall response: strength and stiffness deterioration and pinched hysteresis. Information from the database is used to develop fragility functions, damage states, and scopes of repair for seismic performance assessment of buildings and safety-related nuclear structures incorporating squat reinforced concrete walls.