Assessment of the Effect of Design Parameters of Pressurized Sand Dampers from Component Testing

Abstract

This study presents results from cyclic testing on various configurations of a recently developed pressurized sand damper in which a steel sphere is moving within a cylindrical tube filled with sand that is under pressure. The experimental campaign investigated the effects of the key design parameters of the damper, namely, the effect of the clearance between the moving sphere and the cylindrical tube and the effect of the overall length of the damper to its force output. The recorded force–displacement loops when normalized to the strength of the pressurized sand damper reveal remarkable order with stable behavior and confirm that the force output is nearly rate-independent. The paper also presents recorded force–displacement loops where the sphere mounted on the piston rod is replaced with a bolt where only the bolt head and nut are protruding from the moving piston rod. With this configuration, the pinching behavior of the pressurized sand damper at longer strokes is suppressed without generating large forces at longer strokes. The increasing need for structures to meet acceptable performance levels during earthquake and wind excitation has led to the development of various high-performance design and retrofit strategies. Supplemental damping is a widely accepted response-modification strategy for structures where energy is dissipated in dedicated, specially designed energy dissipation devices. Motivated by the recent failures and displacement limitations of existing energy dissipation devices, this paper examines the behavior of an innovative, reliable, long-stroke, low-cost energy dissipation device in which a steel sphere is moving within a cylindrical tube filled with sand that is under pressure. One of the novel aspects of the proposed pressurized sand damper is that it dissipates energy through the hysteretic behavior of sand that can be enhanced by controlling the externally exerted pressure on the sand. The experimental campaign investigates the effects of the key design parameters of the damper, namely, the effect of the clearance between the moving sphere and the cylindrical tube in association with the effect of the overall length of the damper to its force output.