Behavior of UHPC columns confined by high-strength transverse reinforcement under eccentric compression

Abstract

This paper presents the experimental and analytical studies on the compressive behavior of ultra-high performance concrete (UHPC) columns confined by high-strength transverse reinforcement under eccentric compression. Nine columns including test variables of spacing, strength and arrangement type of transverse reinforcements, steel fiber content and eccentricity were tested to analyze the load-lateral deflection behavior, failure modes and carrying capacity. The experiment results showed that the deformation capacity, peak load and residual carrying capacity of UHPC columns confined by high-strength transverse reinforcement under eccentric loading were significantly better than those of ordinary-strength transverse reinforcement. Reducing the spacing of transverse reinforcement and increasing the volume fraction of steel fiber could also improve the ductility and carrying capacity of UHPC columns. Then, a mesoscale model was proposed to characterize the tensile behavior of UHPC which considered the fiber inclination, fiber-matrix interface bonding and fiber embedded length. Based on the proposed tensile model, a simplified method for calculating the carrying capacity of UHPC columns under large eccentric compression was developed, where the tensile behavior of UHPC and the confinement effect of transverse reinforcements were considered. The errors between the theoretical and test values were within 10%, indicating that this method can be used to guide the design of UHPC columns.