The mechanical performance of curved bridges under the action of an earthquake is complex. To obtain the influence of seismic parameters on the seismic response of curved girder bridges, this paper relies on a large slope small-radius curved steel box girder bridge (LSCGB) and selects seismic wave incidence angle, vertical component of ground motion, and site category as seismic parameters to carry out nonlinear time history analysis. Based on the analysis results of the case bridge, it is shown that the torsional vibration of the first 10 modes of LSCGB is significant, the modes are dispersed, and the contribution of high-order modes of vibration cannot be ignored. The most unfavorable seismic wave incidence angle is in the direction of 45°∼60° counterclockwise Angle from the central connection line of Pier No. 1 and Pier No. 4 of the bridge. The seismic response of the curved bridge components increases with the vertical seismic intensity, and the influence on displacement responses is more significant. The basic vibration period of curved girder bridges built on soft soil sites is extended by approximately 18.23%, and the seismic response of key components increases with the softening of the site soil. Therefore, when analyzing the seismic response of LSCGBs, the influence of vertical component of ground motion and site category should not be ignored.

In highway expansion and reconstruction projects, existing slopes often lead to significant variations in pier heights, forming Irregular Slab-Column Bridge Structures (ISCB). When subjected to seismic loading, such structures exhibit complex mechanical behavior, thereby highlighting the necessity of seismic mitigation design. This study is based on an irregular double-column slab-column highway bridge structure (with a short column of 3 m and high columns of 4 to 9 m) and conducts seismic response analysis using a finite element model. Subsequently, buckling-restrained braces (BRBs) were introduced to evaluate the influence of BRB force ratio on seismic mitigation performance. On this basis, an optimization design method was proposed based on the relationship between the BRB stiffness factor and force ratio. By adjusting the ratio between the BRB force ratio and the computed BRB stiffness factor KF, optimal seismic mitigation and self-centering performance of the structure can be achieved under earthquake loading. This approach effectively prevents local over-deformation and unbalanced responses, enhancing overall seismic performance. The results indicate that the short column exhibits a larger seismic response. When the short column is 3 m and the high column is 6 m, the disparity in seismic responses between the two columns tends to diminish with increasing high column height. The incorporation of BRBs can significantly reduce the structural base shear, reinforcement strain at the column base, and displacement at the column top. Moreover, the reduction in seismic response becomes more pronounced with increasing BRB force ratio. The proposed optimization design method takes into account both the seismic mitigation performance of the BRBs and the self-centering capability of the ISCB. Using this method, the optimal BRB design parameters for the example ISCB are determined (FR _BRB =0.3, KF = 3.3). The proposed method for integrating BRB components into bridge pier design can significantly enhance the seismic performance of the prototype structure, promote rapid functional recovery following strong earthquakes, and serve as a novel strategy for the seismic mitigation design of ISCB structures.

Combining the distribution characteristics of seismic hazard data in the log-log space and the features of the classical power-law model, a new seismic hazard model based on quadratic polynomials was proposed, and its application on actual seismic hazard data of various cities was briefly discussed. Then, by analyzing the composition of the analytical solution of the power-law model, a semi-analytical solution based on the new hazard model was derived to solve the engineering demand parameter (EDP) demand hazard and seismic risk probabilities, and the accuracy of the solution was verified by numerical integration. Next, the case study proved that the proposed semi-analytical solution has higher computational accuracy compared to the classical power-law model. Finally, the proposed new seismic hazard model and semi-analytical solution were used to conduct seismic risk analysis of a high-speed railway bridge.