Transverse seismic mitigation of long-span RC light flexible arch bridge with BRBs under long-period ground motions

To improve the lateral seismic performance of light flexible arch bridges under long-period ground motion, buckling restrained braces (BRB) can be arranged between bent piers. A new type of high-pier long-span RC arch bridge was taken as the research object to illustrate the special features of its structural system. The conditions of near-field ground motions with or without pulse, far-field motions with or without long-period parts were selected to analyze the dissipative effect of BRB on the whole bridge piers and columns and its variation trend of damage state. The results showed that the light flexible arch bridge suffered higher demand under the long-period ground motions. BRB can effectively reduce the deformation and bending moment demand with increased shear force of the column feet. Displacement related BRB applied to arch bridges with flexible system has quite efficient mitigation and dissipation, under the permanent displacement of near-field impulse ground motions and abundant low-frequency components of far-field long-period ground motions. While, due to the low displacement spectrum values of near-field non-pulse and far-field ordinary excitations, response would be generally amplified under these two types of earthquakes. BRB changes the force path transforming part of bending moment into shear and axial force at the joint of the columns. The influence of high-order mode of slender columns increases with BRB being equipped compared to that without, which resulted in sudden change of the bending moment envelope. At the same time, the damage of the columns without BRB was also greatly alleviated. The influence of high-order mode exerted light effect on damage behavior of the highest columns. The damage of the top section of pier and column with BRB could be reduced, due to the vibration coupling between column and arch rib, its bottom sections were alleviated under minor earthquakes. The damage status of the bottom section of the transition pier was relatively more serious. Displacement energy dissipation BRB can effectively improve the lateral seismic performance of soft arch bridges under long-period ground motions. © 2023, Central South University Press. All rights reserved.