考虑非均质和混凝土拉伸性能的梁损伤理论研究

Research on Damage Theory of Beam Considering the Heterogeneity and Tension Damage of Concrete

摘要: 考虑钢筋混凝土梁中钢筋、混凝土性质不同所引起的梁的非均质性和拉伸区混凝土的作用，引入混凝土拉伸损伤，建立了新的考虑混凝土损伤演化的梁理论。研究了混凝土收缩及荷载长期效应对损伤演化和服役寿命的影响，重点考察混凝土损伤演化过程和拉伸区拉应力对寿命的影响，建立了新的梁的挠度计算公式，获得了梁的寿命模型。以适筋钢筋混凝土试验梁为算例，并将分析结果与试验结果加以对比，验证上述理论和寿命模型的正确性。运用上述所建理论，以某大桥为工程背景，建立了该钢筋混凝土桥用于损伤分析的有限元模型，研究了该钢筋混凝土桥梁结构的安全服役性能，预测了其服役寿命。结果表明：所建立的梁理论能较准确地描述钢筋混凝土梁服役过程中的损伤演化和开裂过程，基于该理论所得到的中和轴位置与荷载以及荷载与挠度的关系曲线与测试得到的曲线吻合较好，误差在1%~10%之间；发展的修正的挠度计算公式能较准确地计算梁在长期荷载下的挠度，误差在2%~15%以内，依据该公式所得到的服役寿命具有一定程度的可靠性。

Abstract: Considering the heterogeneity of reinforced concrete beams due to different properties of steel and concrete and the tension performance of concrete at tension zone, the tension damage of concrete was introduced, and a new beam theory considering the damage evolution of concrete was established. The effect of concrete shrinkage and long-term load on damage evolution and service life was discussed, and the key issue was focused on the damage evolution process and the influence of tension stress on service life. A new beam deflection equation and a life calculation model were established. A reinforced concrete test beam was analyzed, and the results were compared with the experimental results to verify the validity of the above theory and the life model. Based on the established theory, the finite element damage analysis model of a reinforced concrete bridge was established to study its security service performance and predict its service life. The results show that the established beam theory can accurately describe the damage evolution of the reinforced concrete beam and the cracking process. The curve between the neutral axis position and load and that between the deflection and load are in good agreement with the testing curves, and the error is between 1% and 10%. The developed deflection calculation formula can accurately calculate the deflection of beam under long-term load, and the error is between 2% and 15%. The service life based on this formula has a certain degree of reliability.