Calculation approach for flexural capacity of reinforced UHPC beams
Peng Fei1,2 Fang Zhi1,2
1. Key Laboratory of Building Safety and Energy Efficiency of the Ministry of Education, Hunan University, Changsha 410082, China;
2. College of Civil Engineering, Hunan University, Changsha 410082，China
Abstract：Ultra-high-performance concrete (UHPC) is a newly developed material that has ultra-high strength, high toughness and high durability, and shows a promising prospect in practical applications. Because steel fibers can effectively resist the development of cracks and lead to the increased flexural capacity of reinforced UHPC beams, the tensile capacity of UHPC is usually included in the flexural capability analysis of UHPC members. Nowadays, various calculation methods for determining the flexural capacity of reinforced UHPC beams have been proposed. However, great differences in accounting for the contribution of tensile zone of UHPC in literature can be observed, indicating that further studies shall be necessary. Hence, in this study, the calculation approach of ultimate flexural capacity of UHPC beams was investigated. Firstly, an analysis program of normal-section flexural capacity of the reinforced UHPC beams was used to perform a detailed parametric study. The analysis results showed that the reinforcement ratio, beam height, steel fiber length, prestressing level and cross-sectional shape were the main parameters affecting the flexural contribution of UHPC in the tensile zone. Based on a multiple regression analysis of the numerical results, a unified equation was developed for the tensile strength reduction factor k of UHPC in the tensile zone. By introducing a reduction factor of kf for the tensile flange area, the influence of different cross-sectional shapes was considered. On this basis, a simplified calculation approach for the flexural capacity of reinforced UHPC beams under different flexural failure modes was derived. It was found that the predicted flexural capacities obtained from the proposed approach were in good agreement with available experimental results of 115 reinforced UHPC beams.
