钢筋UHPC矩形截面受弯构件的钢筋应力简化计算

为建立钢筋UHPC矩形截面受弯构件的钢筋应力简化计算方法，首先基于UHPC结构计算的基本假定建立了钢筋应力数值计算方法，然后推导并修正了考虑UHPC抗拉贡献的钢筋应力简化公式，最后通过与国内外文献相关试验结果进行对比，对所提出的钢筋应力简化公式的适用性进行了验证。结果表明：①数值计算方法所得钢筋应力预测值与实测值整体吻合良好，证明了该方法的有效性。②由于忽略了UHPC的抗拉贡献，直接采用GB 50010—2010规范和JTG 3362—2018规范推荐钢筋应力公式计算所得UHPC构件的钢筋应力误差较大。③根据UHPC结构计算基本假定推导出UHPC受弯构件开裂截面钢筋应力简化公式，并结合参数分析结果建议简化公式中系数α取值0.85，β取值0.50；钢筋应力在125~400 MPa范围时，简化公式预测效果较好；但当钢筋应力在40~125 MPa范围时，由于过高估计UHPC的抗拉贡献，简化公式预测结果明显偏小，甚至出现负值。④为避免简化公式过高估计UHPC抗拉贡献，改进了UHPC受拉贡献系数β的取值方法，进而得到了钢筋应力修正公式；修正后钢筋应力计算值在裂缝发展阶段内，与实测值、数值分析值均整体吻合良好，且与其他文献的钢筋应力试验值吻合也较好，表明修正公式的适用性也较好，可为UHPC结构设计规范的编制提供参考。

Simplified Calculation of Reinforcement Stress in Reinforced UHPC Bending Members with Rectangular Sections

To establish a simplified method of calculating the reinforcement stress of ultra-high performance concrete (UHPC) flexural members with rectangular sections, a numerical calculation method was first proposed based on the calculation assumptions of the UHPC structure. Next, a simplified calculation formula considering the tensile contribution of UHPC was derived and further modified by correcting the coefficient of UHPC tensile contribution. Finally, the applicability of the simplified correction formula was proved by the test results presented in this paper and other publications. The research results indicate the following:① The calculated rebar stress based on the numerical calculation method agrees well with the measured value, which indicates its effectiveness. ② The calculated reinforcement stress based on the formulae in the GB 50010-2010 and JTG 3362-2018 codes show a large deviation. This is because the tensile contribution of UHPC is ignored. ③ Combined with the assumptions used in the UHPC structural calculations, a simplified calculation formula for the reinforcement stress in cracked UHPC flexural members is derived. By combining parameter analysis, the coefficients α=0.85, β=0.50 in the simplified formula is suggested. When the reinforcement stress ranges from 125 to 400 MPa, the simplified formula performs effective predictions. However, when the reinforcement stress is in the range of 40-125 MPa, the simplified formula value is significantly lower than the measured value and numerical analysis value, and furthermore, negative reinforcement stress appears. This is because of the overestimation of the tensile contribution of UHPC. ④ To avoid the overestimation of UHPC tensile contribution, the coefficient of UHPC tensile contribution β is further corrected in the modified formula. During the crack development stage, the modified value of the reinforced bar stress agrees well with the measured value and numerical analysis value. Moreover, the calculated value of the modified formula is also in good agreement with the test values in other studies, which indicates that the modified formula is applicable and can provide a reference for the compilation of design specifications for UHPC structures.