Assessing how bridges and other critical infrastructure will perform during earthquakes is a central problem in earthquake engineering. That problem becomes even harder near active faults, where ground motions can be highly complex and conventional analysis methods may not faithfully represent real hazard conditions. In a study published January 29, 2026, in Civil Engineering Sciences, researchers from Shijiazhuang Tiedao University and Hebei Earthquake Agency proposed a new framework designed to address that gap.
The method, called magnitude-based incremental dynamic analysis (MIDA), replaces one of the most common practices in seismic performance assessment: selecting historical ground motion records and scaling them to different intensity levels. According to the paper, that traditional workflow can introduce subjectivity and nonphysical distortion, which in turn may inflate structural response variability and reduce the reliability of performance evaluation. MIDA instead uses physics-based ground motion simulations tied to earthquake magnitude, allowing the seismic input to remain consistent with the source, path, and site conditions of the scenario being studied.
To test the approach, the team applied MIDA to a near-fault single-pylon cable-stayed bridge and compared the results with those from conventional IDA. The researchers simulated 11 earthquake magnitude levels, from service-level events to the maximum credible earthquake, and tracked damage using the curvature ductility ratio at the tower base. They found that MIDA generally predicted lower structural demand than IDA at the same PGA level and delayed the apparent onset of nonlinear behavior. In MIDA, the bridge first entered the nonlinear stage at about 0.7g, compared with about 0.5g in IDA.
The difference became more important at higher hazard levels. Under service-level, design-basis, and maximum-considered earthquakes, both methods indicated that the bridge tower remained in the elastic stage. But under the maximum credible earthquake scenario, the 84th percentile response in MIDA stayed below the threshold for extensive damage, while the corresponding IDA result exceeded that threshold. In other words, the conventional method tended to paint a more conservative and potentially less realistic picture of structural performance.
The study also found a major difference in response dispersion. At low hazard levels, MIDA showed greater variability because it preserved the natural spatial heterogeneity of near-fault ground motions. As earthquake intensity increased, however, MIDA's dispersion decreased and stabilized, while IDA's dispersion grew sharply in the nonlinear range. In the maximum credible earthquake scenario, the coefficient of variation was 95.3% for IDA, nearly twice the 51.5% reported for MIDA. The authors argue that much of the excess variability in IDA comes not from the hazard itself, but from inconsistent record selection and amplitude scaling.
"Current engineering practice needs assessment methods that are not only convenient, but physically credible," Chao Luo said. "Our results show that when near-fault ground motions are modeled in a way that is consistent with earthquake magnitude and site conditions, the predicted structural performance is more stable and realistic." This language reflects the paper's central conclusion that MIDA improves the physical consistency and precision of seismic performance assessment for near-fault structures.
The immediate significance of the work is methodological, but the practical implications are broader. A more realistic assessment framework can help reduce bias in evaluating bridges and other critical structures exposed to extreme ground motions. The study identifies a clear path forward for performance-based seismic assessment: use hazard-consistent, magnitude-conditioned simulations to better match the physical reality of near-fault earthquakes. The paper states that this approach fills an important methodological gap in current practice and provides a scalable basis for future seismic reliability analysis.
Other contributors include Jingjing Li, Hao Wang and Xueliang Rong from the School of Civil Engineering at Shijiazhuang Tiedao University in Shijiazhuang, China; and Xiaoshan Wang from the Hebei Earthquake Agency.
This research was supported by the National Natural Science Foundation of China (Grant No. 52378171), the Scientific Research Project of Higher Education Institutions in Hebei Province (Grant No. CXZX2025050), the Natural Science Foundation of Hebei Province (CN) (Grant Nos. E2022210095 and E2024210049), and the S&T Program of Hebei (CN) (Grant No. 216Z5402G).
