Reliability analysis of torsional capacity of reinforced ultra-high performance concrete beams and determination of partial factor for materials
Zhou Jiale1,2 Li Chuanxi1,2 Chen Zhuoyi1,2 Feng Zheng1,2 Fang Changle1,2 Yan Yibin1,2
1. Key Laboratory of Safety Control of Bridge Engineering Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China;
2. Key Laboratory of Hunan Province of Green Construction and Maintenance of Bridges and Buildings,
Changsha University of Science & Technology, Changsha 410114, China
Abstract：The tensile strength of UHPC significantly affects the torsional capacity of UHPC members. The calculation method of UHPC is different from that of conventional concrete. For the purpose of checking whether the reliability level of the proposed formula meets the corresponding specification requirements, the statistical parameters of the tensile strength of UHPC and model errors of the proposed formula are obtained from the literature. Based on the comprehensive consideration of key design parameters, including load combination, stirrup reinforcement, UHPC tensile strength and reinforcement strength, the Monte Carlo method was used to calculate reliability indexes of 3240 different design scenarios. Based on the results of reliability indexes, the influences and corresponding sensitivity analysis of the above key design parameters were investigated. The results show that the reliability level of the proposed formula satisfies the specification requirements, and its average reliability indexes are far beyond the target reliability indexes. For the higher tensile strength grade and the larger partial factor for materials, the reinforcement ratio has more influence on the reliability index. The reliability indexes are significant influenced by the tensile strength of UHPC but feebly influenced by the reinforcement strength. To make full use of the tensile strength of UHPC, the partial factors for materials are suggested for different tensile strength grades based on the reliability analysis (the partial factors for materials are 1.25, 1.17, and 1.11, respectively, for different tensile strength grades). Finally, the corresponding design values of tensile strength are also recommended as 3.45, 5.67, and 9.01MPa, respectively.
