Perforated Plate Dampers with added secondary stiffness

A study was performed to develop and validate a new steel plate damper system, called the Perforated Plate Damper (PPD). The system consists of a steel plate with holes located in unique geometric configurations to produce high levels of yielding. Additional bent-plate straps are added to the system to limit the total elongation of the perforated plate allowing the device to dissipate energy through multiple yielding cycles. The system is intended to be installed in a tension-only braced frame structure.;The study involved three principal tasks: (1) progressively developing the damper system through an iterative process of design and physical testing; (2) analyzing a nonlinear finite element model of the central perforated plate to understand the complex yielding of the device; and, (3) using a Single Degree of Freedom (SDOF) dynamic analysis to examine the dynamic characteristics of a structural system utilizing such a device.;The physical testing and analytical analyses confirmed the benefits of the added bent-plate straps. These straps create a tri-linear stiffness curve that allows the system to yield and then be restrained at excessive deformations, thereby prolonging the effectiveness of the device.;The benefits of the complete PPD system with secondary stiffness were further studied and illustrated in the SDOF analysis. In this analysis earthquake ground motions of various magnitude and behavior were used in a dynamic time-integration model to compare an elastic braced frame structure to a non-linear system utilizing the PPD.;It was found that the tension only nature of the system combined with accumulated permanent deformation creates a range of zero resistance displacement. When the structure moves through this range of zero resistance, it is in effect uncoupled from the input ground motion and thus avoids a significant portion of the input energy. Because the stiffness of the damper system is continuously shifting from high resistance to little or no resistance, the system avoids much of the input energy for high magnitude events, regardless of the ground motion characteristics.;The PPD system with secondary stiffness is shown to be a viable energy dissipation mechanism when designed in a tension-only braced frame structure.