In-service condition assessment of pan-girder bridges

Abstract

Pan-girder (PG) bridges became popular in Texas, USA, in the 1950s and 1960s as a viable alternative for short-span bridges due to their speed of construction, low-labour requirements and cost–effectiveness. However, these bridges were designed for lighter live loads than the current AASHTO HL-93 loading, resulting in gradual decline in their usage. Existing PG bridges may have various structural and non-structural deteriorations because they are nearing or have crossed their service lives. In this study, the existing condition of four selected PG bridges in the Dallas–Fort Worth metroplex were visually inspected to assess their current condition. The bridges exhibited significant concrete spalling, cracking and crushing, resulting in exposed and corroded steel rebars. The newest bridge, built in 1992, experienced less severe damage than the other three bridges built in 1955–1971. The bridges’ safety could be compromised due to deteriorations and lighter design live loads. Therefore, the following recommendations were made: (a) glue a polyvinyl chloride pipe on the form-lowering holes extending beyond the concrete surface of the arch to minimise water infiltration and related damage; (b) conduct load testing and ratings to verify the structural safety and load-carrying capacity of the deteriorated bridges; and (c) retrofit to upgrade the existing bridge condition and safety and mitigate against further damage.