PEER has just published Report No. 2014/19 titled “Seismic Response of a Hybrid Fiber-Reinforced Concrete Bridge Column Detailed for Accelerated Bridge Construction” as a new addition to the PEER Report Series. It was authored by Wilson Nguyen, William Trono, Marios Panagiotou, and Claudia P. Ostertag.
With the expected rehabilitation and replacement of damaged reinforced concrete bridges to occur in the next several decades, an opportunity exists to design bridge columns that have an accelerated construction schedule, which would reduce costs related to traffic closures and productivity loss, and to design columns that exhibit enhanced crack resistance, which would reduce damage from seismic events and long-term environmental degradation. This study investigates the feasibility of using a precast hybrid fiber-reinforced concrete (HyFRC) tube element as the exterior shell of a bridge column, which then has its hollow core filled with plain concrete once cast within a foundation. By isolating the fiber-reinforced concrete casting in the precast phase, fabrication of the tube element becomes a well-controlled process, alleviating concerns about the reduced cast-in-place workability associated with fiber-reinforced concrete, and allowing the column to take advantage of the fibers’ enhancement to concrete mechanical properties.
The 1:4.5 scaled tube column had a longitudinal steel ratio of 1.2% and volumetric transverse steel ratio of 0.87%. To accommodate nonlinear deformations, the column utilized a rocking behavior at its base by unbonding the column’s longitudinal reinforcement from the concrete near the base.
The seismic performance of the column was evaluated after subjecting it to static uni-directional cyclic loading. The column was able to withstand drift ratios as high as 13.1% without losing axial load capacity, and longitudinal rebar did not fracture up to drift ratios of 9.5%. Compression damage of the column was relatively low by the end of the test, as spalling of concrete cover was not witnessed. Compared to a similarly sized rocking column cast entirely with hybrid fiber-reinforced concrete, the tube column maintained a higher lateral load capacity at large drift ratios, and had less observed structural damage.