A Magnitude-Based Incremental Dynamic Analysis Method for Seismic Performance Assessment of Near-Fault Structures

Seismic performance assessment of near-fault critical structures remains challenging, as conventional intensity-based incremental dynamic analysis (IDA) approaches suffer from subjective ground motion selection and nonphysical amplitude scaling, which introduce artificial dispersion and compromise performance assessment reliability. This study proposes a magnitude-based incremental dynamic analysis (MIDA) method that replaces empirical record selection and scaling with physically consistent ground motion simulations conditioned on earthquake magnitude. Various earthquake scenarios, ranging from service level to maximum considered earthquakes, are simulated, and the curvature ductility ratio at the tower base is adopted as the damage measure to evaluate the seismic performance of a near-fault cable-stayed bridge. Results indicate that MIDA yields markedly lower dispersion and improved physical consistency in structural responses than IDA after entering the nonlinear stage. In maximum credible earthquake scenarios, the coefficient of variation of structural response reaches 95.3% in IDA but is only 51.5% in MIDA, highlighting the improved reliability and accuracy of seismic performance assessment. By addressing the critical limitations of conventional IDA approaches, MIDA substantially enhances the physical consistency and precision of seismic performance assessments for near-fault structures. It offers a scalable methodological basis for consistent seismic performance evaluation and supports reliability-informed engineering decision-making in near-fault hazard zones.