Influence of RC jacketing on the seismic vulnerability of RC bridges

• Fragility curves for bridges retrofitted with RC Jackets.
• Retrofitted bridges subjected to ground strong motions.
• Seismic vulnerability of single-column piers reinforced with RC jackets.
• Shear base capacity of single-column piers reinforced with RC jackets.

Bridge’s piers can be damaged by the action of intense earthquakes. These elements are the most important component of the structural stability of a bridge system. After the occurrence of an earthquake or after updates in the design code, the piers may require an intervention to improve their strength and stiffness capacities. For a long time, RC jacketing has been used as a suitable technique to provide additional strength and to improve the ductile behavior of columns under seismic loads. There are several studies related to the behavior of bridges retrofitted with RC jacketing, but there is a lack of quantitative evaluations for this technique regarding the seismic vulnerability of a bridge. This work investigates RC bridges with a substructure conformed with a bent cap joined to a RC column retrofitted with RC jacketing. The effects of the retrofit system are based on fragility curves estimated through a parametric analysis that considers six retrofit cases, and several seismic scenarios to determine four limit states. The results quantify the effect of the jacket thickness and the longitudinal reinforcement ratio for the probability of reaching several limit states of behavior. In all cases, RC jacketing increases the shear capacity of the pier, and it reduces the bridge’s seismic vulnerability. It was also found that the longitudinal steel ratio is the parameter with the most influence on the piers’ seismic vulnerability, and the results allow inferring the most suitable parameters that can be used as RC jacketing.