配筋UHPC梁抗扭承载力可靠度分析及材料分项系数的确定

超高性能混凝土(Ultra-High Performance Concrete, UHPC)抗拉强度对抗扭承载力的贡献不可忽略，其构件抗扭承载力计算公式不同于常规混凝土。为检验该公式的可靠度水平，该文基于试验结果和公开文献中的相关数据，得到了UHPC抗拉强度及抗扭承载力模型不定性统计参数。在综合考虑荷载组合、箍筋配筋率、UHPC抗拉强度和钢筋强度等关键参数的基础上，运用Monte Carlo方法对3240种组合下UHPC梁抗扭承载力状态进行了可靠度分析，考查了各关键参数对可靠指标的影响并进行了敏感性分析。结果表明：按现行UHPC规范计算配筋UHPC梁抗扭承载力，其可靠度水平满足要求且可靠指标远高于目标指标；UHPC抗拉强度等级越高且材料分项系数取值越大，配筋率对可靠指标的影响越显著；其抗拉强度对可靠指标影响较显著，钢筋强度对可靠指标的影响可忽略。为充分利用UHPC抗拉强度，基于敏感性分析结果，结合目标可靠指标，校准了不同等级UHPC抗拉强度材料分项系数(强度等级UT05、UT07和UT10的材料分项系数分别为1.25、1.17和1.11)。最后，给出了不同等级抗拉强度建议设计值，可分别取3.45MPa、5.67MPa和9.01MPa。

Reliability analysis of torsional capacity of reinforced ultra-high performance concrete beams and determination of partial factor for materials

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.