Experimental and numerical investigation of the seismic performance of steel-reinforced ultra-high performance concrete beams

To investigate the seismic performance of steel reinforced ultra-high performance concrete (UHPC) beams, four steel-reinforced UHPC beams and one steel-reinforced normal concrete (NC) beam were designed and fabricated for comparison. Low-cycle reversed loading tests were conducted, and key parameters such as reinforcement ratio, steel ratio, stirrup ratio, and concrete type (UHPC and NC) were evaluated. Finite element models of the steel-reinforced UHPC and NC beams were developed using the OpenSees platform, and the results were validated against test data. A formula for calculating the flexural capacity of the UHPC beam cross-section was proposed. The results showed that the hysteretic curves of the steel-reinforced UHPC beams were full, and the skeleton curves declined slowly after peak load, indicating excellent ductility and energy dissipation capacity. Increasing the reinforcement ratio and steel ratio effectively enhanced the peak bearing capacity of the beams. When the stirrup ratio was increased from 0.67 % to 1.3 %, the peak load increased by only 3.8 %, but the energy dissipation capacity after the peak load significantly improved. Compared to the steel-reinforced NC beams, the peak bearing capacity of the steel-reinforced UHPC beams improved by 30.7 %. The proposed formula for calculating the flexural capacity of the steel-reinforced UHPC beams based on the neutral axis position showed good agreement with the test and numerical results. The findings of this study provide a theoretical and experimental basis for the application of steel-reinforced UHPC beams in seismic regions.