Control of thermal deflection in concrete structures using iron-based shape memory alloys

Abstract

Mitigating the structural damage caused by thermal expansion cycles is a primary objective in the design of concrete structures, such as bridges or buildings. One method to achieve this goal is the introduction of shape memory alloys (SMAs) as a replacement of traditional steel reinforcements in concrete structures. SMAs exhibit a characteristic known as “shape memory effect,” which allows the recovery of large deformations through the alloy’s martensite and austenite phase transformations. This effect gives SMAs an inherent advantage over steel. The purpose of this paper is to characterize the effect of an embedded SMA rod on a concrete system undergoing a thermal cycle, and to optimize the configuration of these materials. To achieve these ends, a system is modeled in Abaqus, a software suite for finite element analysis, consisting of a concrete block with an embedded, prestrained SMA rod, in which the concrete and SMA material properties have been determined from experimentation and secondary research. A set of the SMA’s properties (max transformation strain, coefficient of thermal expansion, stress influence coefficients, and volume fraction of SMA to concrete) are iteratively altered to produce characterization of the rod’s effect on the system, and then the same set are again altered using a multi-objective optimization tool to minimize deflection and maximize the temperature where concrete damage occurs. This approach is a cost-effective method to characterize the effects of these material properties and produce results that can be utilized in future projects where SMAs are deployed in large-scale concrete structures.