Experimental seismic behavior of ultra-high performance concrete columns with high strength steel reinforcement

Ultra-High Performance Concrete (UHPC) is an advanced cementitious composite material that exhibits high ductility and durability with superior mechanical properties, e.g. compressive strength in excess of 22 ksi (150 MPa) and sustained post-cracking tensile strength greater than 0.7 ksi (5 MPa). These characteristics have promoted UHPC to be considered for new construction applications specially for next-generation bridge structures. Currently, UHPC is commonly used in limited structural applications, such as joints and connections between precast structural elements. However, there is a growing interest in larger UHPC applications and new designs of full structural members as the UHPC market keeps growing and material becomes more available. One potential application for structural elements is full UHPC columns, which is the focus of this study. This paper presents an experimental investigation of the structural and seismic behavior of large-scale full UHPC columns reinforced with conventional and high strength steel reinforcement. The UHPC columns were tested under combined axial and quasi-static cyclic lateral loading at the University of Nevada, Reno. The testing program included four columns where the seismic performance of three different columns with grade 100 reinforcement is compared with a reference UHPC column with regular grade 60 reinforcement. Thus, the varied experimental parameters included the longitudinal reinforcement ratio and grade as well as the transverse reinforcement ratio. Results demonstrate that UHPC columns have reasonable ductility and drift capacity. Moreover, higher reinforcement ratio or grade is needed to better utilize the superior mechanical properties of UHPC and recommended to inform future design.