A Step Toward Proposing a Force Reduction Factor for Hybrid GFRP/Steel Reinforced Concrete Columns Under Earthquakes

The use of hybrid reinforcement (Stee/GFRP) system was proposed in the present study as a vital solution for overcoming corrosion problem with a proper energy dissipation capacity. This study also presents a preliminary step toward developing a force reduction factor for concrete columns reinforced with hybrid reinforcement. Nonlinear finite-element analysis (FEA) was used as a tool to achieve the research target. A novel FEA model for RC columns that captures the behavior of concrete columns solely reinforced with steel or GFRP bars and have been previously published by the first author, was first summarized. The study was then extended to test the effect of using hybrid reinforcement in terms of crack patterns, failure modes and load–lateral displacement hysteretic response. The force reduction for the hybrid RC specimen was also estimated. The reported test results clearly revealed that properly detailed hybrid RC columns have a recoverable and self-centering ability. The hybrid RC column sufficiently achieved the maximum drift meeting the limitation of most building codes. Acceptable levels of energy dissipation accompanied by relatively small residual forces, compared to the steel-reinforced column, were observed. The force reduction factor was suggested to be taken 2.5 for hybrid RC columns.