Arch rib-straight brace damage pattern and the seismic performance evaluation under earthquakes

Transverse braces are one of the most vulnerable parts of rib arch bridges under earthquakes. In order to study the interaction between arch rib and braces under earthquakes and its influence on the damage pattern of the arch rib-brace structure, a simplified arch rib-straight brace analysis model which based on a prototype arch bridge was firstly established. Twenty comparison groups were set to study the influence of brace stiffness, layout position and quantity on the dynamic characteristics and elastic stability of the arch rib-brace structure. Five typical arch rib-brace damage patterns were identified based on the formation path and distribution of plastic hinges which were obtained through the static nonlinear analysis. The nonlinear time-history analysis method was applied to comparatively investigate the dynamic response characteristic and seismic performance in different damage patterns through the proposed energy dissipation coordinating index ϕ and comprehensive evaluation ξ. The results indicate that both static elastic-plastic analysis and nonlinear time-history analysis can obtain 5 types of arch rib-brace damage patterns that are mutually verified; the seismic responses and performance of the arch rib-brace structure are obviously superior when subjected to the brace→rib→springing (BRS) damage pattern compared to the other four damage patterns, and the peak strain values of the brace, arch rib and springing are very close to each other in the BRS damage pattern, indicating a coordinated mode of energy dissipation among the three components. The proposed indexes ϕ and ξ can efficiently represent the seismic performance of the identified arch rib-brace damage patterns. When the absolute value of ϕ is closer to 0 or the value of ξ is smaller, the arch rib-brace structure can develop a more coordinated mechanism of energy dissipation and thus gain a better overall seismic performance. When the design of straight braces makes the arch-brace system meet the BRS damage pattern, the structure has the optimal seismic performance. The damage pattern identification approach and the evaluation indexes that proposed in this research can provide a reference for the design of straight braces and seismic performance evaluation of similar arch bridges in the future. © 2024, Central South University Press. All rights reserved.