Experimental Studies of Shape Memory Alloy Reinforced Concrete Columns under Seismic Loads

The primary source of providing tensile strength in concrete members has been generally reinforcing steel. An exception to this practice is the limited use of fiber reinforced polymer (FRP) bars, FRP tubes, and FRP fabrics used for retrofit. Steel provides an attractive material to compensate for the low tensile strengths of concrete because it has high strength in both tension and compression, its thermal expansion coefficient is close to that of concrete, its ability to take different shapes, its wide availability, and its relatively low cost. Under extreme loads, however, a steel-reinforced structural member undergoes extensive yielding and large permanent deformations. This could be a major detriment to the serviceability of the structure after the event. In contrast to steel, superelastic shape memory alloys (SMAs) overcome this shortcoming because of their ability to recover nearly the entire strain even when deformed to strains as much as 8%, thus reducing the permanent displacement. This extended abstract and the conference presentation provide a summary of what has been learned in several tests of reinforced concrete members utilizing SMAs and the associated analytical modeling.