Seismic Retrofit of Concrete Shear Walls With Tension-Only Sma Braces

Abstract eng:
A retrofitting technique, using tension-only superelastic Shape Memory Alloy (SMA) braces, was developed to enhance the performance of seismic deficient squat concrete shear walls. The SMA braces were designed to improve re-centering (minimize residual deformations) and to control shear deformations, while improving strength, ductility and energy dissipation capacities. Two squat reinforced concrete walls: an original and a companion retrofitted wall were tested to investigate the benefits of the tension-only SMA braces on the seismic response. Retrofitting of the concrete wall was based on a bi-diagonal layout where two crossing tension-only SMA braces were connected to the base and top of the wall. The walls were tested to failure with incremental cyclic loading. The experimental results demonstrated that the tension-only SMA braces are capable of improving the seismic response of squat reinforced concrete walls. The retrofitted wall experienced higher strength, greater energy dissipation and reduced permanent deformation. Furthermore, the re-centering properties of the SMA contributed to the reduction of pinching of the hysteretic response due mainly to the clamping action of the SMA bracing while recovering its original length.

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