Seismic fragility analysis of wood sheathed CFS shear wall under near- and far-field earthquakes

Abstract

Wood-based panel shear walls are among the most common lateral load-bearing systems for light steel frame (LSF) structures. While design and construction aspects have been addressed in published codes, this research aims to evaluate performance levels and their probabilities for wood-based shear wall panels, both quantitatively and qualitatively. Eighteen frames with varying characteristics, including sheathing material, screw spacing, and panel configuration, were modeled and analyzed using OpenSees software. Incremental dynamic analysis (IDA) was conducted under near-field and far-field earthquake conditions. Considering the importance of fragility curves in assessing the seismic damage of the structures, these curves were plotted and the probability of occurrence for each performance levels regarding to the intensity of various earthquakes were determined. The results reveal that near-field earthquakes impose a higher probability of structural damage, with a 20 % greater likelihood of exceeding performance thresholds at the same S_a(T₁, 5 %) compared to far-field earthquakes. Fragility curves developed for immediate occupancy (IO), life safety (LS), and collapse prevention (CP) levels indicate that the CP threshold is reached with a 50 % probability at 0.53 g for near-field and 0.77 g for far-field earthquakes in OSB-sheathed walls. The response modification factor (R-factor) was evaluated, and a value of 6.5 was found suitable for design based on FEMA P695 guidelines. This study insights for performance-based seismic design, demonstrating that parameters like sheathing material, screw spacing, and panel configuration significantly affect seismic resilience.