PRESTRESSING CONCRETE BEAMS WITH SHAPEMEMORY ALLOYS WIRES

Abstract

The study deals with the use of shape memory alloys (SMAs) tocreate prestresses in concrete prismatic beams. Nickel-titaniumSMA wires with suitable transformation temperatures are firststretched in the martensite state at ambient temperature. Thenthey are placed onto the surface of the beams. A thermal cycle isapplied to transform the martensite to austenite, in order toactivate the shape memory effect in the wires. The strainevolution in the concrete beams is measured with strain gauges.An active prestress effect is clearly observed in the beams duringthe procedure until cooling down to ambient temperature. Theinfluence of the initial stretch of the wires and the transformationtemperatures is discussed.