Numerical Investigation on Plastic Hinge Length of Ultra-high Performance Concrete Column under Cyclic Load

The unique features of ultra-high performance concrete (UHPC) in terms of damage tolerance, energy absorption, and deformability make this material suitable for applications in piers or columns of structures. However, few studies were available in literature regarding seismic test under cyclic load to investigate the plastic hinges of UHPC columns. As the cost of testing is relatively high, this study focuses on determining the plastic hinge lengths of UHPC columns under cyclic load based on numerical analysis. Analysis is conducted using finite element method (FEM) with the software OpenSees, and calibrated by test results. Parametric study is performed to investigate the effect of horizontal loading angle, axial force ratio, reinforcement diameter, yield strength of reinforcement, and length of the column on the plastic hinge length. The applicability of the empirical models of reinforced concrete (RC) columns for UHPC columns is discussed, and a multivariate regression expression for the equivalent plastic hinge length of a UHPC column is proposed. The results indicate that the length of the plastic zone decreases with the increase in axial load ratio, and monotonously increases with the increase in the length of the column. The trend of initial increase followed by a decrease in the length of plastic zone is observed with the increase in horizontal loading angle, reinforcement diameter, and yield strength of reinforcement. The empirical models are found to underestimate the plastic deformation of UHPC columns. The proposed expression for equivalent plastic hinge length has a reasonable agreement with FEM results.