UHPC梁开裂弯矩适用计算方法研究

Study on the Applicable Calculation Method of the Cracking Moment of UHPC Beam

为探究超高性能混凝土(ultra-high performance concrete,UHPC)梁抗开裂性能,通过4点弯曲试验研究了不同纤维类型、掺量及配筋率对梁受弯抗开裂性能的影响.基于试验结果,结合理论分析及数值模拟,对比了不同开裂弯矩计算方法结果,并探究了多种UHPC受拉本构对开裂荷载计算值的影响.分析了不同方法所得结果的差异及原因,提出了一种超高性能混凝土梁开裂弯矩计算方法.结果表明:UHPC抗拉强度是影响梁开裂弯矩的最直接因素,提高梁配筋率、增大纤维掺量、改变纤维形状有利于提高梁的抗开裂性能,但作用有限;截面平衡法、等效截面法计算结果偏大,美国FHWA规范的计算结果与试验值较为吻合,但相关性不好;收集相关文献数据验证表明,本文方法能准确预测超高性能混凝土梁开裂弯矩.

In order to explore the crack resistance property of ultra-high performance concrete(UHPC)beams,the effects of different fiber types,fiber volume fractions,and reinforcement ratio on the flexural cracking resistance of beams were studied by four-point bending test.Based on the test results,combined with theoretical analysis and numerical simulation,the applicability of different calculation methods of cracking moment was compared.The influence of various UHPC tensile constitutive models on the calculated cracking load was explored.The differences of the results obtained by different methods were analyzed,and the causes of error were discussed.Then,a new method for calculating the cracking moment of ultra-high performance concrete beams was proposed.The results show that the tensile strength of UHPC is the most direct factor affecting the cracking moment of beams.Increasing the reinforcement ratio of the beam,increasing the fiber volume fraction,and changing the fiber shape are all beneficial to improving the crack resistance of beams,but the effect is limited.The calculation results of the section equilibrium method and the equivalent section method are too large.The American FHWA specification calculation results are in good agreement with the experimental values,but the correlation is not good.Finally,the literature data was collected to verify that the calculation method proposed in this paper can accurately predict the cracking moment of ultra-high performance concrete beams.