USE OF SHAPE MEMORY ALLOY WIRESFOR THE CREATION OF PRESTRESS STATESIN CONCRETE BEAMS

Abstract

The study deals with the use of shape memory alloys (SMAs) tocreate prestress states in concrete prismatic beams. Nickel-titanium SMA wires with suitable transformation temperatures areused to this purpose. The wires are first stretched in a martensiticstate at ambient temperature. Then they are placed onto the surfaceof the beams. A thermal cycle is applied to transform themartensite to austenite, in order to activate the shape memoryeffect in the wires. The strain evolution in the concrete beams ismeasured with strain gauges. A prestress effect is clearly observedin the beams during the procedure until cooling down to ambienttemperature. The influence of the initial stretch of the wires and thetransformation temperatures is discussed.