ABSTRACT
The bridges’ piers are the structural element whose failure may led to the bridge’s collapse. A retrofit technique commonly implemented in damaged piers, is the reinforced concrete (RC) jacketing. The objective of this work, is to study the efficiency of RC jacketing in the seismic vulnerability of bridges conformed by circular RC piers, located on the Pacific Coast of Mexico. For this, fragility curves are estimated as a function of two parameters selected to define the RC jacketing, jacket’s thickness and longitudinal steel reinforcement, under different seismic scenarios representatives of earthquakes generated on the subduction seismic source, and four limit states of behavior. The parametric study consists of four basic bridges and six retrofitting cases for each of them. Figure 1 presents a transverse cross section of the bridges studied. Bridges’ transverse cross section. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig198_1.tif"/>
To estimate the efficiency in reducing the seismic vulnerability of RC bridges conformed by a single column, it was estimated the median peak ground acceleration (PGA) required to lead the bridges to four limit states, namely: slight, moderate, severe and collapse. These limit states were calculated as a function of the displacement ductility demands (Choi et al., 2004). Figure 2 presents an example of the results estimated from the fragility curves. Median PGA needed for a bridge with span-length of 20-m and pier height of 6-m to reach a predefined limit state of behavior. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig198_2.tif"/>
The analysis of all the results obtained from the parametric study let to conclude that this retrofit technique increases the piers’ base shear capacity and reduces the bridges’ seismic vulnerability. Further, the results lead infer that the RC jacket’s longitudinal steel is the variable that has the most important effects in decreasing the bridges seismic vulnerability. Looking for aids that help to the engineer practitioner to determine the expected pier’s drift for an expected PGA in order to make a decision to retrofit a bridge that may be vulnerable to the occurrence of an earthquake of important magnitude, there were estimated two expressions relating the pier’s drift with an expected PGA that are valid for pier height between 6 and 10-m.
The general conclusion is that RC jacketing is a retrofit system that can reduce the seismic vulnerability of bridges with geometry as the one considered in this work if they are located close to a subduction seismic source.
