基于可靠度的钢筋UHPC受弯梁材料分项系数研究

为确保规范的计算公式满足可靠度要求，对在编《公路桥涵超高性能混凝土应用规范》正截面抗弯承载力表达式中的UHPC材料分项系数进行分析与校准。基于现有文献，收集整理中国共648个UHPC抗压强度、210个抗拉强度和53根受弯梁的试验数据，得到相关变量的统计参数。随后建立4 158根UHPC受弯梁的计算空间，采用蒙特卡洛模拟对其进行可靠指标计算与敏感性分析，考察截面类型、材料强度、截面纵筋率及活恒载效应比等参数对钢筋UHPC受弯梁可靠指标的影响。基于分析，对计算空间进一步细分，以截面纵筋率为0.05、活恒载效应比为0.05~0.5的T形梁截面可靠指标均值达β_T=4.2为目标，校准钢筋UHPC梁受弯状态下的UHPC材料分项系数。研究结果表明：抗力统计参数中，UHPC抗压强度、抗拉强度以及梁抗弯承载力计算误差均不拒绝正态分布；受弯状态下UHPC梁截面可靠指标主要受活恒载效应比与截面纵筋率的影响，而材料强度影响较小；活恒载效应比越低，截面纵筋率越高，其可靠指标越低；当活恒载效应比从0.05升至1.0时，可靠指标提升幅度较大；且活恒载效应比大于0.5时，可靠指标均高于4.2。当截面纵筋率从0.005升至0.05时，可靠指标下降较为明显；而当截面纵筋率高于0.05后，可靠指标几乎保持不变；同等条件下，矩形截面梁的可靠指标要稍高于T形截面梁;建议钢筋UHPC梁受弯状态下的UHPC材料分项系数取值为1.3。

Reliability-based Research on Material Partial Factor of Reinforced UHPC Flexural Members

In order to ensure that the design formulas meets the reliability requirement, the ultra-high performance concrete (UHPC) material partial factor in the equations of flexural capacity was analyzed and calibrated in Code Specification for Application of Highway Ultra High Performance Concrete Bridge and Culverts. Firstly, Based on the existing papers, a total of 648 UHPC compressive strength tests, 210 tensile strength tests and 53 flexural beams tests in China were collected, and the statistical parameters of relevant variables were obtained. Then a computing space of 4 158 UHPC flexural beams was established, in which a Monte Carlo simulation was used to conduct a reliability analysis to find out the influence of section type, material strength, longitudinal reinforcement ratio and live load ratio on the reliability index of reinforced UHPC flexural beams. Based on the analysis, the computing space was subdivided. Then with the goal that the mean reliability index of T-shaped section beams reaches β_T=4.2 with longitudinal reinforcement ratio of 0.05 and live load ratio between 0.05 and 0.5, the UHPC material partial factor under flexural was calibrated. The results show that: Among the resistance statistical parameters, the compressive strength and tensile strength of UHPC and the calculation errors of flexural capacity of UHPC beams do not reject the normal distribution. The reliability index of UHPC beam under flexural is mainly affected by live load ratio and longitudinal reinforcement ratio, while the material strength has little influence. The lower the live load ratio and the higher the longitudinal reinforcement ratio, the lower the reliability index.When the live load ratio rises from 0.05 to 1.0, the reliability index increases greatly. And when the live load ratio is greater than 0.5, the reliability index is higher than 4.2. When the longitudinal reinforcement ratio increased from 0.005 to 0.05, the reliability index decreased significantly. And when the longitudinal reinforcement ratio is higher than 0.05, the reliability index remains almost unchanged. Under the same condition, the reliability index of rectangular section beam is slightly higher than that of T-shaped section beam. The UHPC material partial factor under flexural is suggested to be 1.3.