Degradation of Wind and Seismic Resistance of Metal Roof–Photovoltaic System Connections by Repeated Wind Loading

The standing seam metal roof (SSMR) system, widely used in long-span buildings, is highly susceptible to long-term wind loads. The integration of a roof-top photovoltaic (PV) system into an SSMR system fundamentally alters the wind load distribution, shifting from a relatively uniform pressure over the entire roof surface to concentrated forces at discrete points where PV supports are anchored. This change in wind load results in stress concentrations around the SSMR-PV system connections and is likely to cause wind-induced damage. Such damage progressively degrades the connection’s wind-load and seismic resistance over time. However, existing Load and Resistance Factor Design (LRFD) methods often neglect the long-term effects of such damage, potentially leading to designs unable to maintain adequate resistance against design wind and seismic loads throughout the SSMR-PV system’s service life. To address this gap, this study investigated the wind-induced damage pattern of SSMR-PV system connections and quantitatively assessed its influence on the connection’s wind-load and seismic resistance via a series of displacement-controlled cyclic loading tests. Given high-intensity wind load, critical damage patterns—standing seam collapse and fatigue cracks—reduced the connection’s vertical and horizontal resistance by up to 19.2% and 52.5%, respectively. Given low-intensity wind load, critical damage patterns—standing seam creep and bolt loosening—reduced the connection’s vertical and horizontal resistance by up to 14.5% and 59.2%, respectively. These findings suggest varying resistance reduction factors in LRFD procedures of the SSMR-PV system connections by regions with different wind load intensities.