Geometric Optimization of a Single-Particle Impact Damper for Mode-Specific Vibration Suppression in Multi-Storey Structures

This study introduces a Tuned Single-Particle Impact Damper (TSPID) developed for mode-selective vibration suppression in multi-degree-of-freedom (MDOF) structures. While particle impact dampers are typically recognized for their broadband effectiveness around the fundamental resonant frequency, their ability to achieve mode-selective attenuation in resonant modes of MDOF structures has received comparatively limited investigation. This work combines numerical parametric studies with experimental validation on a scaled five-story shear-type building to show that a single geometric parameter, the clearance gap, enables effective and robust mode-selective suppression. Three performance metrics are used: modal Hi;1 norm (peak response at each resonance i), total vibration energy, and inter-storey drift (ISD). When optimized for the first mode, the TSPID achieves average reductions of 95% in vibration energy, 93% in ISD, and 86% in modal H1;1 norm across all floors. When it is optimized for the second mode, the corresponding reductions remain substantial (85% in vibration energy, 79% in ISD, and 66% in modal H2;1 norm). Performance is largely insensitive to the choice of impact-surface material (polyurethane versus polyethylene foam, with differences below 5% across all metrics), confirming that energy dissipation is governed primarily by impact dynamics rather than exact restitution or stiffness values. Numerical impact sequencing analysis further reveals that effective suppression coincides with approximately two regular impacts per excitation cycle at sufficient mean impact velocity, supporting the role of impact sequencing and impact velocity in the observed mode-selective suppression. The normalized clearance D is identified as a physically meaningful design parameter that inherently accounts for the amplitude-clearance interaction governing impact effectiveness. These results establish a practical, geometrically simple design framework for mode-targeted vibration control. By bridging general particle-damper effectiveness and mode-selective suppression, the TSPID offers high efficacy, low cost, and inherent robustness, making it particularly attractive for resonant-dominated civil and mechanical structures.