Subject Area

Civil Engineering

Abstract

This study presents a discrete element method (DEM) numerical model to elucidate mechanical behavior, particle crushing, and anisotropy evolution within a pressurized sand damper (PSD) subjected to cyclic loading. Computational simulations of the PSD under different initial pressures and stroke amplitudes were conducted and compared to experimental results. Good agreement was achieved between the DEM model and experimental results for the different cases. Force-displacement, particle crushing, shear, and normal stresses along with geometric and mechanical anisotropy degrees were closely monitored in different areas of the PSD. Dissipated energy was also monitored and used to calculate the specific damping capacity.

Employing elongated, triangle, pyramid, cube, and hexagon particle shapes as well as crushable and uncrushable particles as sand grains revealed that the closest results to the experiments are obtained when using elongated crushable particles. It was observed that reducing the container length for a specific particle shape results in a small increase in contact force. Furthermore, changes in the stroke amplitude, initial pressure, and particle shape had minimal influence on the dynamic force generation.

The results show that the majority of crushing occurs in the vicinity of the center of the PSD and within the first loading cycle, mainly in the smallest group size. Increasing stroke amplitude significantly influenced particle crushing, whereas increasing initial pressure was less considerable. In addition, a direct relationship between the PSD's direction of movement with shear and normal stresses and anisotropy degree was observed. Moreover, the contribution of mechanical anisotropy was more considerable than the geometric anisotropy to the overall anisotropy degree.

Regarding dissipated energy, an increase in stroke amplitude resulted in higher dissipated energy whereas an increase in initial pressure had a minor influence on the dissipated energy. Based on the dissipated energy, it was found that the specific damping capacity was nearly equal to one for all cases studied.

Computational simulations were conducted to explore the influence of different PSD porosities and positions along a cantilever beam's length when subjected to an impact load. The results highlighted the significance of fine particles within a particle damper and demonstrated the impact of global and local porosity on the damper's performance. It was observed that reducing the particle damper's porosity correspondingly decreases the beam's displacement while increasing the kinetic energy within the damper. Additionally, it was concluded that the majority of the kinetic energy is attributed to the translational motion of the particles.

The impact force was significantly influenced by the global and local porosities, where having small and closely matched values of both parameters resulted in higher impact forces. In addition, the time intervals between sub-impacts were also affected by the damper's porosity. It was revealed that an increase in initial pressure reduces the beam's displacement. Based on the results obtained, the optimal location for the particle damper was determined to be at the point where displacement reduction is required, rather than directly underneath the impact load's location.

This research will enhance the understanding of particle interactions within the innovative pressurized sand damper (PSD). It will also lay the groundwork for future studies on the performance of PSDs and particle dampers made from various materials attached to structures.

Degree Date

Spring 2024

Document Type

Dissertation

Degree Name

Ph.D.

Department

Civil and Environmental Engineering

Advisor

Usama El Shamy

Format

.pdf

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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Available for download on Friday, April 30, 2027

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