Full-Scale Tests of Bridge Steel Pedestals

Overheight vehicle collisions can cause major damage to bridges. To address the issue of limited vertical clearance heights and reduce the likelihood of impact damage, the Georgia Department of Transportation has implemented a program to elevate major highway bridges using very short columns referred to as steel pedestals. The process to elevate the bridges and install the steel pedestals is cost effective and efficient, resulting in minimum disruption to highway traffic. However, in practice, these pedestals are not detailed to provide end fixity, so they add considerable flexibility to the superstructure supports and potentially make the bridge more susceptible to instability and damage from seismic loads. Therefore, there is a need to evaluate how these steel pedestals will perform under the low-to-moderate earthquakes expected in this region. A full-scale 12.2?m (40?ft) dual steel girder simply supported bridge elevated with 500?mm (19?in.) and 850?mm (33?1/2?in.) steel pedestals is constructed based on typical field procedures. The full-scale bridge specimen is subjected to quasistatic unidirectional reversed cyclic loads to determine the strength and deformation capacity of the steel pedestals and overall system performance. The kinematics, mechanisms, and load–displacement hysteretic relationships of the bridge steel pedestals and its components are presented. Results show that the steel pedestals undergo kinematic rigid body motion, dissipate energy, and demonstrate reasonable deformation and strength capacities when subjected to quasistatic, reversed cyclic loads.