Modeling and Validation of RC Columns Seismically Retrofitted Using Shape Memory Spiral

Abstract

This analytical work focuses on utilizing the experimental results of reinforced concrete (RC) columns that are tested under lateral cyclic loading after being retrofitted using a new active confinement technique. In the experimental work, the plastic hinges of nonductile columns are wrapped with prestrained shape memory alloy (SMA) spirals. The spirals are then heated to activate the shape memory feature in the SMA spirals, which consequently results in applying large external confinement pressure on the columns. Experimental cyclic tests show that this innovative type of confinement is superior to conventional passive confinement methods. This work presents a validated analytical modeling technique for RC columns that are actively confined with SMA spirals. The proposed analytical modeling technique is proven to be effective in capturing the global behavior of the columns. The developed analytical models are then used to conduct a parametric study to examine the sensitivity of the confined RC column to several parameters including external active confinement pressure induced by SMA spirals, volumetric ratio of internal steel transverse and longitudinal reinforcements, column's diameter and slenderness ratio, and the level of the axial load. Multi-factor analysis of variance (ANOVA) is used to design the parametric study. The ANOVA serves as a statistical tool to assess the impacts of possible interactions between the studied parameters on the columns' behavior. The goal is to determine the most significant interactions that ought to be studied and discard those interactions with low level of impact. The results of the parametric study are used to develop recommendations related to the optimum confinement pressure and column properties that are most important in designing the new retrofitting technique.