钢筋UHPC受弯构件裂缝宽度计算方法研究

为建立钢筋UHPC受弯构件的裂缝宽度计算方法，对6根钢筋UHPC梁进行四点抗弯试验，分析试验梁的裂缝发展过程和分布规律，以此为基础评估了现有规范公式计算钢筋UHPC受弯构件裂缝宽度的适用性，给出考虑UHPC抗拉贡献的钢筋UHPC受弯构件的钢筋应力计算方法和裂缝宽度建议计算公式，并通过国内16根钢筋UHPC梁的97组有效裂缝宽度试验结果对给出的裂缝宽度建议公式的适用性进行验证。研究结果表明：①UHPC梁表面裂缝宽度小于0.25mm时，裂缝宽度基本呈线性规律扩展，裂缝数量不断增加，裂缝间距逐渐减小；裂缝宽度超过0.25mm后，裂缝宽度迅速扩展并形成主裂缝，裂缝数量基本不变，裂缝间距趋于稳定，裂缝分布密而细，呈现出多元开裂现象。②直接采用GB 5010-2010规范和CECS 38-2004规范的裂缝宽度公式计算钢筋UHPC受弯构件的裂缝宽度误差较大。③基于UHPC材料特性，提出考虑UHPC抗拉作用的钢筋UHPC受弯构件开裂截面的钢筋应力计算方法，可较好地预测钢筋UHPC受弯构件开裂截面的钢筋应力。④结合试验数据和分析，对GB 50010-2010规范中平均裂缝间距、钢筋应变不均匀系数、构件受力特征系数进行修正，给出钢筋UHPC受弯构件裂缝宽度计算公式，修正后的建议公式计算值与文章试验值吻合良好，且与法国UHPC规范公式预测结果相比离散性更小。⑤建议公式的裂缝宽度计算值与收集的裂缝宽度试验数据库的试验值之比的平均值为0.99，标准差为0.19，表明建议公式适用性良好，可为UHPC结构设计规范的编制提供参考。

Calculation method for crack width of reinforced UHPC flexural components

In order to establish the method for calculating the crack width of reinforced UHPC flexural components, the four-point bending tests on six beams of reinforced UHPC were carried out, and the development and distribution of cracks in the test beams were investigated. Based on the experiments, the applicability of crack width formula in the existing design specification to predicting the crack width of reinforced UHPC flexural components was evaluated. In addition, the calculation method of rebar's stress in the reinforced UHPC flexural members considering the contribution of tensile strength of UHPC as well as the prediction formula for crack width of UHPC were proposed. Furthermore, the applicability of the proposed crack width formula was verified by97 sets of effective crack width results from 16 UHPC beams in China. The results showed that: ① When the surface crack width of UHPC beam was less than 0.25mm, the crack width appeared to propagate linearly, the number of cracks continuously increased, and the spacing of cracksgradually decreased; when the crack width exceeded 0.25mm, however, the crack width rapidly increased so that the main crack was formed, the number of cracks remained basically unchanged, and the crack spacing tended to be stable. Additionally, the cracks in UHPC beams were narrow and densely distributed, and with the multiple-cracking behavior. ② For the crack width of reinforced UHPC flexural components, quite large deviations between the test results and calculated results by referring to the code of GB 5010 2010 and CECS 38-2004. ③ Based on the material properties of UHPC, a calculation method for the rebar's stress in the cracked section of the UHPC flexural members, which considers the UHPC tensile behavior and can predict the rebar's stress in the cracked section very well, was proposed. ④ Based on the test results and analysis, the average crack spacing, the uniformity coefficient of steel strain and the characteristic coefficient of the component specified in the code of GB 50010-2010 were modified, and the formula for calculating the crack width of UHPC flexural members was given. The calculated results from the modified formula agreed well with the experimental results, exhibiting smaller deviations when comparing to the predicted results from French UHPC code. ⑤ The average value for the ratios of the predicted crack width to the experimental crack width from the experimental database on the crack width of UHPC was 099, and its standard deviation was 0.19, indicating the good applicability of the proposed formula. Therefore, the proposed calculation method for crack width can be referred to by the UHPC structural design code.