UHPC局部受压承载力计算方法

为合理地计算UHPC构件的局部受压承载力，建立了有、无间接钢筋UHPC的局部受压试验数据库，以此为基础分析和评估了NF P 18-710、CECS 38:2004、DBJ 43/T 325—2017和JTG 3362—2018中的局部受压承载力计算公式；基于UHPC局部受压试验数据库提出了考虑混凝土强度和钢纤维影响的UHPC局部承压修正系数和间接钢筋影响系数，进而修正了JTG 3362—2018的局部受压承载力计算公式。研究结果表明:无间接钢筋UHPC的局部受压承载力试验值与NF P 18-710、CECS 38:2004、DBJ 43/T 325—2017和JTG 3362—2018计算值之比的均值分别为0.97、0.81、1.33和1.09，有间接钢筋UHPC的局部受压承载力试验值与CECS 38:2004、DBJ 43/T 325—2017和JTG 3362—2018计算值之比的均值分别为0.91、1.31和1.13；各规范公式的混凝土局部受压承载力公式未充分反映混凝土抗压强度和钢纤维的影响，间接钢筋的局部受压承载力计算公式未充分反映约束面积比、混凝土抗压强度和钢纤维的影响；NF P 18-710可较好地预测无间接钢筋UHPC的局部受压承载力，CECS 38:2004计算所得UHPC的局部受压承载力偏大，且间接钢筋的局部受压承载力预测结果离散性大，DBJ 43/T 325—2017和JTG 3362—2018的计算结果偏保守。有、无间接钢筋UHPC的局部受压承载力试验值与JTG 3362—2018修正公式的预测值之比的均值分别为1.00和1.04，标准差均小于0.20，因此，JTG 3362—2018修正公式可较好地预测有、无间接钢筋UHPC的局部受压承载力，可为国内UHPC桥梁结构设计规范的编制提供参考。 

Calculation method of UHPC local compressive bearing capacity

To reasonably calculate the local compressive bearing capacity of UHPC members, the local compression test database of UHPCs with and without indirect reinforcement was developed. Based on the database, the calculation formulae of local compressive bearing capacity in codes of NF P 18-710, CECS 38: 2004, DBJ 43/T 325—2017, and JTG 3362—2018 were analyzed and evaluated. A UHPC local compression correction factor and an indirect reinforcement influence factor were proposed to analyze the effects of concrete strength and steel fibers used in the UHPC local compression test database. Subsequently, the local compressive bearing capacity calculation formula in JTG 3362—2018 was modified. Research results indicate that the average ratios of experimental local compressive bearing capacities of UHPCs without indirect reinforcement to the calculated values by UHPC codes of NF P 18-710, CECS 38: 2004, DBJ 43/T 325—2017, and JTG 3362—2018 are 0.97, 0.81, 1.33, and 1.09, respectively. The average ratios of experimental local compressive bearing capacities of UHPCs with indirect reinforcement to the calculated values by CECS 38: 2004, DBJ 43/T 325—2017, and JTG 3362—2018 are 0.91, 1.31, and 1.13, respectively. Therefore, the calculation formulae of concrete local compressive bearing capacity in different codes do not completely reflect the influences of concrete compressive strength and steel fibers. Similarly, the local compressive bearing capacity calculation formulae of indirect reinforcement do not completely reflect the effects of constrained area ratio, concrete compressive strength, and steel fibers. NF P 18-710 can better predict the local compressive bearing capacity of UHPC without indirect reinforcement. CECS 38: 2004 overestimates the local compressive bearing capacity of UHPC, thereby diverging the estimated bearing capacity of indirect reinforcement. As for DBJ 43/T 325—2017 and JTG 3362—2018, their calculation results are relatively conservative. The average ratios of the experimental local compressive bearing capacities to the predicted values by the modified JTG 3362—2018 formula are 1.00 and 1.04 for UHPCs with and without indirect reinforcement, respectively, and the standard deviations in both cases are less than 0.20. Therefore, the modified formula in JTG 3362—2018 can better predict the local compressive capacities of UHPCs with and without indirect reinforcement, and thus it can provide a reference for the design specifications of domestic UHPC bridge structures. 1 tab, 13 figs, 31 refs.