A Rate-Independent Phenomenological Model for the Characterization of Pressurized Sand Dampers

This study presents the mathematical characterization of the recently developed pressurized sand damper (PSD) in which a steel sphere or bolt is moving within a cylindrical tube filled with sand under pressure. The experimental results, presented in previous studies, revealed that the force output exhibited by the PSDs is stable, symmetric, and nearly velocity-independent. Thus, the PSDs are response-modification devices that offer rate-independent dissipation. In addition, when tested at various levels of pressure, displacement amplitude, and frequency, the PSD displays hysteresis loops with pronounced pinching. To accurately reproduce their response, a recently formulated phenomenological model [the Vaiana Rosati model (VRM)] is employed. The VRM allows for the evaluation of the output variable by means of analytical closed form expressions or equivalent rate equations; in addition, it captures, with good accuracy, the experimental responses of the PSDs obtained for both periodic and nonperiodic displacement time-histories.