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为解决混凝土非线性特性难以描述的难题,通过MTS815.02岩石电液伺服系统,对圆柱体混凝土试件施加定围压比为0.2的围压,得出C25、C35、C45混凝土在“理想无损伤”状态下的应力-应变曲线;用Ramberg-Osgood公式描述其应力-应变关系,引入损伤变量演化方程,进而得出混凝土一维受压损伤本构模型。通过与实验数据的对比证明了模型的有效性和准确性;详细地分析了无初始损伤条件下配筋梁受弯破坏时的损伤演化过程;计算C25、C35、C45钢筋混凝土梁的受弯承载力。分析结果显示:随着混凝土强度由C25提高到C45,按此模型计算与按规范公式计算所得梁承载力的差异由1.9%升高至2.84%;下降段损伤累积量占总体损伤度的比例由46.26%升高至86.04%。研究表明,本文的分段曲线损伤模型可以较好地模拟梁混凝土的非线性受压过程,并能够给出损伤程度的预测。
In order to solve the difficult problem that the nonlinear characteristics of concrete is difficult to describe, the MTS815.02 rock electro-hydraulic servo system was used to apply the confining pressure with a confining pressure ratio of 0.2 to the concrete specimens. The results show that C25, C35, Stress-strain curve under the condition of “no damage”. The stress-strain relationship was described by Ramberg-Osgood formula, and the evolution equation of damage variable was introduced to obtain the one-dimensional constitutive model of compression damage of concrete. The validity and accuracy of the model were verified by comparison with the experimental data. The damage evolution process of the reinforced beam under flexural failure without initial damage was analyzed in detail. The flexural bearing capacity of C25, C35 and C45 reinforced concrete beams force. The results show that with the increase of concrete strength from C25 to C45, the difference of bearing capacity calculated by this model and calculated according to the canonical formula increases from 1.9% to 2.84%. The ratio of the cumulative damage in the descending section to the overall damage degree is calculated from 46.26% up to 86.04%. The research shows that the model of segmented curve damage in this paper can simulate the nonlinear compression process of beam concrete well and predict the degree of damage.