Shear behaviour of beams strengthened using different Ni-Ti-Nb shape memory alloy wire configurations and design proposal based on the compression chord Capacity model (CCCM)

Abstract

[eng] Shear strengthening of existing structures is often required in cases where shear strength is deficient because shear failures in RC members are associated with brittle collapse. In previous papers, the authors presented an innovative system for active strengthening shear critical-reinforced concrete (RC) beams using shape memory alloys (SMA) to take advantage of the shape memory effect. The authors also presented an approach to design this type of reinforcement based on the Compression Chord Capacity Model (CCCM). This model considers several shear transfer actions, including increased shear strength of the concrete compressed chord due to its confinement. This article presents an experimental study of RC beams with new types of SMA strengthening systems that also improve the shear behaviour of beams. The new types of tested shear strengthening systems are U-shaped external wires to facilitate the construction process by reducing initial imperfections; spiral active SMA wire implanted into a groove in the lower RC specimen part to see if it improves the dowel action effect; spiral active SMA wire only confining the compressed chord to check whether the CCCM predictions in this regard are adequate.