Seismic Response Characteristics and Buckling-Restrained Brace-Based Optimization Design for Irregular Slab-Column Bridge Structures

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.