Static-Dynamic Study on Overturning Stability of Curved Beam Bridges Considering Lane Loads and Near-Field Earthquake Effects

Most existing studies on the overturning stability of bridges focus merely on vertical static loads, while dynamic effects under earthquakes remain insufficiently investigated. This study advances the state-of-the-art by systematically investigating the overturning performance of curved bridges under combined lane loads and near-field earthquake actions. The Anti-Overturning Stability Ratio (AOR, denoted as γ qf )—defined as the the ratio of the anti-overturning moment M ao to the overturning moment M ov —is adopted as the evaluation index. A comprehensive analytical framework is established through static analysis, quasi-static response spectrum analysis, power spectral density (PSD) analysis, and nonlinear time-history analysis. The key procedures include identifying the most unfavorable overturning axis under self-weight; evaluating AOR under lane loads and earthquakes with consideration of non-uniform load distribution, vertical seismic components, and bearing layouts; identifying frequency ranges detrimental to overturning stability via PSD analysis; and computing dynamic AOR using synthesized velocity-pulse ground motions and two natural near-field earthquake records. Furthermore, a modified overturning moment formula incorporating seismic inertia forces and centrifugal effects is proposed, providing a theoretically rigorous evaluation approach for curved bridges under combined static and seismic actions. Results indicate that lane loads generally enhance the anti-overturning capacity by increasing bearing reactions, whereas seismic actions degrade stability by including bearing uplift and enlarging the overturning area and eccentricity. Optimizing bearing configurations (e.g., installing torsional bearings) significantly improves anti-overturning performance. Near-field earthquakes with strong velocity pulses impose particularly adverse effects on single-column-pier curved bridges and require special attention in seismic design. Overall, overturning stability is governed by the combined effects of lane load characteristics, seismic intensity, frequency content, motion direction, and bearing layout, among which near-field pulse-type ground motions present the most critical hazard.