Experimental and Numerical Modal Assessment of Rooftop Photovoltaic Support Structures under Wind-Sensitive Design Conditions

Rooftop photovoltaic (PV) support structures are increasingly used on existing buildings in typhoon-prone regions, yet their preliminary dynamic assessment is often less developed than their static wind-load verification. This study presents a case-based experimental and numerical modal assessment of a rooftop canopy-type PV support structure. A reduced-scale specimen representing an actual rooftop support frame was tested using a biaxial shaking table, and a simplified SAP2000 finite-element model was established to interpret the dominant modal response. The shaking-table tests identified a dominant frequency of approximately 4.17 Hz, while the corresponding numerical model predicted a first modal frequency of 4.19 Hz. The close agreement indicates that the simplified finite-element representation can capture the governing global stiffness of the tested support system. The results further suggest that global lateral flexibility, rather than local member response alone, governs the vibration-sensitive behavior of lightweight rooftop PV support frames. The study provides a practical modal-screening procedure for early-stage structural assessment and design refinement of rooftop PV support systems under wind-sensitive design conditions. Limitations related to scaling, absence of wind-tunnel pressure measurements, and single-case validation are explicitly discussed.