Effect of Volume Tie Ratio in the Engineered Cementitious Composites Plastic Hinges on the Seismic Performance of RC Composite Bridge Columns

The feasibility that the transverse reinforcements in steel-reinforced Engineered Cementitious Composites (ECC) columns could be reduced or even totally eliminated has been experimentally demonstrated. However, due to the effect of the tie volume ratio in ECC plastic hinges on the seismic performance of RC composite bridge columns not being fully clarified as of yet, a numerical study was carried out. In this study, the analytical models based on the fiber element method, by considering the superposition of different lateral confinements resulting from ties and the ECC cover, were used to correlate with a target hybrid-loading experiment. Load-displacement hysteresis, strains in extreme fibers and longitudinal bars in analytical results correlated well with the experiments, verifying the accuracy of the analytical models proposed in this study. Based on the analytical results, it was found that the volume tie ratio had little effect on the stress-strain hysteresis of the ECC cover, but a lower volume tie ratio resulted in more significant nonlinear behavior longitudinally. Finally, the pushover analysis was conducted to investigate the effect of volume tie ratios on the seismic design parameters, and the results showed that a higher volume tie ratio resulted in a limited increase in the maximum allowable displacement for design.