Effects of Axial Load and Tensile Strength on Reinforced UHPC Plastic Hinge Length

Abstract

Researchers have explored the high energy absorption capacity and strength of UHPC materials to improve the seismic performance of structural components. Experimental results in the literature of reinforced UHPC members have indicated superior damage tolerance, higher strength and deformation capacities, and lower potential for collapse across a range of structural components. Investigations into the underlying failure mechanisms have highlighted the significance of the synergy between material tensile strength and reinforcement properties on member flexure response. Although research into the seismic application of reinforced UHPC continues to expand, relatively little is known about the effects of varying axial load on the plastic hinge response of beam-column elements across a range of UHPC tensile properties and reinforcement levels. Therefore, in this study, the effects of varying tensile properties on beam-column elements through numerical simulations across a range of axial load ratios were investigated. Two dimensional numerical models accounting for material nonlinearities (e.g., bond-slip, UHPC tensile strength and strain capacity) were used to capture component responses. Trends in the moment-drift responses and plastic hinge lengths have highlighted the diminishing returns of using higher fiber volume percentages (2%) as higher axial loads tend to relieve tensile demands. Additionally, existing plastic hinge length expressions for RC components were found to over-predict hinge length consistently while those developed for HPFRCC components accurately predict plastic hinge lengths at low axial load levels.