Seismic performance of multi-span RC bridge with irregular column heights

Bridges are essential elements in modern transportation network and play a significant role in a country’s economy. However, it has always been a major challenge to keep bridges safe and serviceable. Modern bridge design codes include seismic detailing in order to ensure ductile behavior, which was absent in the pre-1970 codes that made older bridges vulnerable during earthquakes. The main parameters effecting the performance of bridge (tie spacing, concrete and steel properties, amount of reinforcement) varies significantly from old to modern bridges. The presence of irregularity in column heights is one of the common causes of seismic vulnerability and the non-uniform column height is the most common form of irregularity. In this study, a four span RC box-girder bridge has been considered for different column height configurations. Here, a detailed parametric study has been performed to understand the effects of various factors on the limit states of the individual bridge columns using factorial analysis. Static pushover analyses, incremental dynamic analyses and fragility analyses of bridges with irregular column heights have been conducted to identify the seismic vulnerability of bridges in the longitudinal direction due to irregularity in column height. This study also investigated the difference of conventional force-based approach and displacement-based approach in designing a bridge with irregular column heights. Canadian Highway Bridge Design Code (CHBDC) and AASHTO 2007, like other traditional design codes follow force-based design (FBD) method, which is focused at the target force resistance capacity of the structure. On the other hand, displacement-based design approach focuses on a target maximum displacement of the bridge during the earthquake in a specific zone. Seismic performances of the bridges designed in two different methods have been compared by non-linear dynamic analyses in the longitudinal direction in terms of maximum and residual displacements and energy dissipation capacity.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat