Large-Scale Experimental Evaluation and Numerical Simulation of a System of Nonlinear Energy Sinks for Seismic Mitigation

As a novel dynamic vibration absorber, the nonlinear energy sink has been studied for mitigating structural and mechanical vibration through the last decade. This paper presents a series of large-scale experimental evaluations and numerical simulations on a system of nonlinear energy sink (NES) devices for mitigating seismic structural responses. Two distinct types of NES devices were installed in the top two floors of a large-scale model building structure. In the device system, four Type I NESs employing smooth essentially nonlinear restoring forces were used in conjunction with two single-sided vibro-impact (SSVI) NESs employing non-smooth impact nonlinearities. These NES devices utilize the existing structural mass and space of the model building to realize an integrated design of building structure with non-parasitic control devices. Scaled historic earthquake ground motions were implemented by a large-scale shake table as the base excitation input into the system. Direct comparisons between mitigated and unmitigated structural responses, including story displacement, column strain and base shear force, demonstrate that rapid mitigation of structural responses was achieved by the system of devices. Reductions of both peak and average values of structural responses were clearly observed. The synergistic effects obtained by simultaneously using two types of NES devices were demonstrated. To computationally investigate the mitigation performance of the devices subjected to a wide variety of ground motions, a numerical model was developed for the structure-NES system and two suites of earthquake ground motions representing distinct earthquake intensities were employed. Simulation results demonstrate that mitigation of structural responses caused by diverse earthquake ground motions can be achieved by a system of NES devices

Equivalent Modal Damping, Stiffening and Energy Exchanges in Multi-Degree-Of-Freedom Systems with Strongly Nonlinear Attachments

We consider the response of a linear structural system when coupled to an attachment containing strong or even essential nonlinearities. For this system, the attachment, designated as a nonlinear energy sink, is designed as a nonlinear vibration absorber, serving to dissipate energy from the structural system. Moreover, the attachment not only leads to a reduction in the total energy of the system, but also nonlinearly couples together the vibration modes of the linear structural system. When the structure is impulsively loaded, the nonlinear energy sink serves to both dissipate and redistribute energy, thus enhancing the observed structural dissipation. The effect of the nonlinear attachment on the linear primary system can be quantified in terms of equivalent measures for the damping and frequency of each mode, derived through consideration of the instantaneous energy balance in each mode. The influence of the nonlinear energy sink on the structural response is illustrated with an impulsively forced two-degree-of-freedom primary system, representing a two-story structure, with different types of nonlinear energy sink attached to the top floor. We perform optimization studies in order to design the nonlinear energy sink for optimal shock mitigation of the primary system. The proposed methodology is based only on measured time series without resorting to frequency analysis. As such, it is valid for strongly nonlinear systems as well as for systems with nonsmooth nonlinearities, and is suited to both simulated and experimental results. Finally, an experimental validation of the enhanced dissipation introduced by the nonlinear energy sink is provided, and the experimental response is compared against numerical simulation of the corresponding analytical model to illustrate the effectiveness of the nonlinear energy sink design. Thus, we analytically predict and experimentally verify the efficacy of the nonlinear energy sink to significantly reduce the response of the two degree-of-freedom system subject to shock excitation

Passive Damping Enhancement of a Two-Degree-Of-Freedom System through a Strongly Nonlinear Two-Degree-Of-Freedom Attachment

This work reports on the first experimental study of the broadband targeted energy transfer properties of a two-degree-of-freedom (two-DOF) essentially nonlinear energy absorber. In particular, proper design of the absorber allows for an extended range of energy over which it serves to significantly enhance the damping observed in the structural system to which it is attached. Comparisons of computational and experimental results validate the proposed design as a means of drastically enhancing the damping properties of a structure by passive broadband targeted energy transfers to a strongly nonlinear, multidegree-of-freedom attachment

A Novel Video-Based Patient Education Program to Reduce Penile Prosthetic Surgery Cancellations

Penile prosthetic surgery is an effective treatment for men with erectile dysfunction. Cancellation of surgery is disruptive and costly to patients, physicians, and the healthcare system. This pilot study sought to analyze surgery cancellations and implement a video-based patient education program to decrease surgery noncompletion. Baseline penile prosthetic surgery completion, rescheduling, and cancellation rates among consecutively scheduled surgeries were determined using a national cohort. Selected prosthetic surgeons then implemented Vidscrip, a video-based patient education program. Prerecorded videos were delivered via text message 14 days, 7 days, and 1 day preoperatively, as well as 1 day postoperatively. Subsequent analysis determined noncompletion rates, reasons for noncompletion, surgeon volume, and video utilization. Two-hundred twenty-six surgeries were scheduled in the baseline cohort; 141 were completed, and 85 were rescheduled or canceled. Among the intervention cohort, 290 patients completed, 7 rescheduled, and 37 canceled surgery. After program implementation, the surgery noncompletion rate was reduced compared to baseline (13.2% vs. 37.6%, p 20 cases vs. ≤20 cases: 8.20% vs. 32.0%, p = .35). Video utilization was widely variable among practices (median viewing time 58.6 min, IQR 5.09–113). Penile prosthetic surgery is frequently rescheduled or canceled. Implementing a video-based patient education program reduces surgery noncompletion, improving efficiency and quality of care. Wider implementation is needed to validate these findings, while cost-effectiveness analyses may further support their broad adoption