Shear strength and displacement capacity of squat reinforced concrete shear walls
Adorno-Bonilla, Carlos M.
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Squat reinforced concrete (RC) walls are essential structural components in nuclear power facilities (NPP) and in many civil structures. An adequate prediction of the shear strength and displacement capacity of these elements are important for the seismic design and performance assessment of structures whose primary lateral force resisting system is comprised by squat walls. These walls have aspect ratios less than or equal to 2. Due to their geometry, squat shear walls tend to have shear-dominated behavior while exhibiting strong coupling between flexural and shear responses. This dissertation presents an evaluation of current expressions for the prediction of peak shear strength and displacement capacity of squat RC walls available in US design codes and in the literature. An updated database was assembled with the results of moderate to large-scale experimental tests walls with shear-dominated failures and subjected to cyclic loads found in the literature. Key parameters influencing the peak shear strength and displacement capacity were identified and improved predictive equations were developed by calibration against the available data. Multiple-linear regression analyses were used to develop the predictive equations. It was found that the peak shear strength of such walls has not been adequately addressed by current US code equations in ASCE 43-05 and ACI 349-13 / ACI 318-14 since there is significant scatter on the predictions. It was also found that the peak shear strength equations in current US codes and standards tend to over-estimate the strength of squat RC walls with rectangular cross section, as well as to considerably under-estimate the peak shear strength of the squat RC walls with enlarged boundary elements considered in the assembled database. Experimental data suggested that allowable drift limits requred by ASCE 7-10 design code provisions for damage control are unconservative for the case of squat walls. Finally, two simplified analytical modeling approaches were presented. A Fiber-Based Model with flexure-shear interaction and a Macro-Hysteretic model were studied. A tri-linear backbone, calculated with the developed strength and displacement capacity expressions, was proposed to use in conjunction with the Macro-Hysteretic model for the nonlinear-cyclic analysis of squat RC walls.