Vibration Control with Shape-Memory Alloys in Civil Engineering Structures

摘要

The superelastic behavior exhibited by shape-memory alloys shows a vast potential for technological applications in the field of seismic hazard mitigation, for civil engineering structures. Due to this property, the material is able to totally recover from large cyclic deformations, while developing a hysteretic loop. This is translated into a high inherent damping, combined with repeatable re-centering capabilities, two fundamental features of vibration control devices.;An extensive experimental program provides a valuable insight into the identification of the main variables influencing superelastic damping in Nitinol while exploring the feasibility and optimal behavior of SMAs when used in seismic vibration control.;The knowledge yielded from the experimental program, together with an extensive bibliographic research, allows for the development of an efficient numerical framework for the mathematical modeling of the complex thermo-mechanical behavior of SMAs. These models couple the mechanical and kinetic transformation constitutive laws with a heat balance equation describing the convective heat problem. The seismic behavior of a superelastic restraining bridge system is successfully simulated, being one of the most promising applications regarding the use of SMAs in civil engineering structures.;A small-scale physical prototype of a novel superelastic restraining device is built. The device is able to dissipate a considerable amount of energy, while minimizing a set of adverse effects, related with cyclic loading and aging effects, that hinder the dynamic performances of vibration control devices based on passive superelastic wires.