Design of SMA-Brace Devices for the Seismic Retrofit of Steel CBF

Retrofit interventions are often performed by introducing in structures dissipative devices able to improve the global seismic response particularly in terms of energy dissipation capacity. In the case of Concentric Braced Steel Frames (CBF), these devices are generally introduced in the form of brace elements made of different materials and based on different dissipation mechanisms. Their design is strictly related to both the characteristics of the selected device and, also, to the own peculiarities of the structural system involved in the retrofit intervention.

The paper presents a simple design approach for the seismic retrofit of non-ductile CBF through the use of Shape Memory Alloys (SMA) brace devices. The approach merges the potentialities of SMA materials and the main peculiarities of the truss-resistant mechanism of CBFs throughout a procedure based on a preliminary phase of assessment, an intermediate phase of requirements evaluation and a final phase of design of the retrofit intervention.

After a detailed explanation of the proposed approach, the results derived from non-linear time-history analyses developed with reference to three and five-story CBFs are presented in the paper.