| Description |
This research investigates the feasibility of using buckling restrained brace (BRB) as a retrofit strategy to improve the seismic performance of reinforced concrete (RC) skewed bridges. The evaluated base case system is a Californian three-span RC bridge with a length of 127.5 m (425 ft.). Initially, different BRBs were implemented in a straight bridge to assess the performance of the retrofitted bridge, and to optimize the BRB configuration. The ASCE 41 methodology was used to scale sets of far-field and near-field ground motions (GMs) to the maximum considered earthquake level. Because of the nonorthogonality of the skewed bridges' major axes, the major and minor GM principal directions were first obtained and then rotated to 11 incidence angles. Nonlinear time history analyses were performed with these different seismic input directions for the original and retrofitted bridges with different skew angles. The maximum seismic responses can be predicted by orienting first one of the principal GM directions to the longitudinal bridge axis, and then rotating the principal directions 90 degrees. It was observed that BRB retrofitting in the column bents mitigates the influence of GM incidence angle. Numerical simulations were performed on the bridges using distributed plasticity models with the hysteretic models that account for strength and stiffness deterioration. Nonlinear incremental dynamic analyses (IDAs) predicted the skewed bridge behavior before and after BRB retrofit until the global collapse limit state. These simulations indicate that BRB components can improve the seismic performance of bridges by decreasing the drift at the bents, and by reducing the steel and concrete strains of the RC columns. Moreover, BRB attracts more shear forces at the bents, reducing the seismic demands at the abutments. Although BRB components greatly improve the bridge's seismic performance, they have negligible effects on the ultimate collapse capacity of the bridges after BRB failure. Nevertheless, the probability of failure is reduced by using BRBs because of the improved performance at low and moderate seismic levels. Analytical methods to predict the additional seismic effects due to skew bridge configuration, as well as the influence of GMs incidence angle, are also proposed in this study. |
