Damage Analysis of RC Frames in the Luding Ms 6.8 Earthquake, China

A M_s 6.8 earthquake struck Luding, China, in September 2022, causing significant structural damages to buildings. Notably, reinforced concrete (RC) frame structures exhibited the failure mode of strong beam–weak column (SBWC), which poses a severe threat to human safety and economic stability. This study investigates the disadvantageous failure mechanisms in RC frame structures, drawing on observations from the author's recent field investigations. Refined finite element models (FEMs) of RC frames were developed to systematically simulate these failure mechanisms. The models enabled an in-depth analysis of structural characteristics, with particular attention to column-to-beam flexural strength ratios (CBFSRs). These ratios were calculated to identify thresholds that can prevent destructive SBWC failure modes and promote the desired strong column–weak beam (SCWB) behavior. The FEM analysis results were validated against real-world earthquake damage phenomena, showing strong consistency in damage patterns. The study also highlights the critical role of external factors in exacerbating structural damage. For example, slope site effects significantly amplified seismic impacts on structures. Furthermore, the influence of non-structural elements such as Que Ti and infill walls was found to increase shear force demands on RC frame columns, further compromising their performance under seismic loads. Based on these findings, the study proposes an optimal range for CBFSRs to achieve SCWB behavior, contributing to safer structural designs. Practical recommendations and considerations are outlined to guide future earthquake-resistant construction practices and mitigate disaster risks effectively.