Search for: All records

The unique mechanical properties of ultra-high performance concrete (UHPC) causes changes in failure modes and ductility in reinforced components. Numerous experiments have shown these materials, and others with similar ductile characteristics in tension, can improve the damage tolerance, strength, and ductility of members subjected to large deformations from seismic loading and similar extreme conditions. The use of these materials, however, has not been systematically studied to understand their application at a system-level performance and design procedures have been complicated due to their unconventional failure mechanism. This project aims to fill this gap by testing a targeted set of components subjected to combined effects of axial loads and bending with variations in axial load ratio and longitudinal reinforcement ratio. Additional experiments are planned to compare performance across other ductile concrete materials with variations in mechanical properties. The experimental results including load-deformation, reinforcement strain, concrete surface strain will be used to understand the parameters that have the highest influence on plastic hinge length and moment-rotation response which can ultimately help to validate analytical models against experiments based on these key parameters. 

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.