Probabilistic Seismic Fragility Assessment of Concentrically Braced Frames under Near- and Far-Field Ground Motions

The use of fragility curves plays a crucial role in assessing seismic damage in buildings. In this study, fragility curves are developed to evaluate the level of damage under different earthquake intensities. Special Concentrically Braced Frames (SCBFs) in mid-rise buildings (۴, ۸, and ۱۲ stories) are investigated. The structures are designed using two different steel grades for the bracing members. The fragility curves are generated through more than ۱۰۰ nonlinear time-history analyses for each frame, using ground motion records with different frequency contents under both near-field and far-field earthquakes. Statistical and probabilistic methods are employed based on inter-story drift as the damage index. The results indicate that, under the same peak ground acceleration, structures with lower-grade steel bracing experience less damage compared to those with conventional structural steel. Furthermore, near-field earthquakes lead to higher drift demands, along with reduced ductility and energy dissipation capacity, due to the sudden input of seismic energy into the structures.

کلیدواژه ها:

Fragility Curves ، Near-Field Earthquake ، Far-Field Earthquake ، X-Bracing ، Low-Grade Steel ، Seismic Behavior