基于离散元的钢筋混凝土梁极限承载力研究

RESEARCH ON ULTIMATE BEARING CAPACITY OF REINFORCED CONCRETE BEAM BASED ON DISCRETE ELEMENT METHOD

通过PFC2D建立考虑骨料级配的钢筋混凝土梁离散元细观数值模型,开展钢筋混凝土梁极限承载力的研究。混凝土标准棱柱单轴压缩模拟验证了混凝土单元细观参数的准确性。通过修改平行黏结模型获得了适用于钢筋模拟的平行-强化黏结接触模型,钢筋单轴拉伸模拟验证了钢筋单元细观参数的准确性。建立了无缺口钢筋混凝土梁离散元数值模型,在此基础上生成预制缺口钢筋混凝土梁数值模型,根据缺口位置及倾角分为9种工况,分析了各工况下梁的裂缝扩展规律及极限承载力。结果表明:缺口位置对裂缝的扩展过程影响较大,一般起裂位置均位于缺口顶端;缺口倾角仅对裂缝扩展初期有影响,后期裂缝依然会沿竖向发展;缺口梁极限承载力约为无缺口梁极限承载力的95%~98%。

A discrete element mesoscopic numerical model which considers the aggregate gradation of reinforced concrete(RC) beams is established by PFC2D.The research on the ultimate bearing capacity and crack propagation law of RC beams is carried out.The accuracy of the meso-parameters of concrete elements is verified by uniaxial compression simulation of concrete standard prisms.Meanwhile,a parallel-hardening contact model which is modified by the parallel bond model is established for steel rebar simulation,and the uniaxial tensile simulation of steel bar has verified the accuracy of the meso-parameters.A discrete element numerical model of unnotched RC beam is established and the numerical model of pre-notched RC beam is generated based on unnotched RC beam.According to the notch position and dip,test conditions are divided into 9 types.The crack propagation law and ultimate bearing capacity of each test condition are analyzed.The results show that the notch position has great influence on crack propagation process,and the crack initiation positions are generally located at the tip of notch.The notch dip only affects the initial stage of crack propagation,and the cracks may continue to grow along the vertical direction in the later stage.The ultimate bearing capacity of pre-notched beam is about95%~98% of that of unnotched beam.