双层混凝土复合梁静动态弯拉破坏模式分析
Analysis of Static and Dynamic Flexural Failure Mode of Double-Layer Concrete Composite Beam

针对无砟轨道层间损伤的问题，开展了双层混凝土在共同受力下协同工作性能的研究.从细观视角出发，运用图像处理技术获得试件表面骨料的分布状态，建立了双层混凝土复合梁的二维细观模型；对混凝土4点弯拉试验进行模拟与验证，探究了加载应变率对混凝土梁弯拉破坏模式、弯拉强度及应力位移关系的影响.研究结果表明：从力-位移曲线和破坏模式两者来看，数值模拟结果和试验结果都较为接近，说明运用细观尺度计算模型模拟混凝土开裂过程的方法是可行的；高加载应变率1×10-2/s、1×10-1/s下，双层混凝土之间的交界面处会出现较大损伤；在1×10-3/s、1×10-2/s、1×10-1/s加载应变率下，最大承载应力分别为1.50、6.41、14.40 MPa，混凝土裂纹由沿薄弱交界面周围扩展的单一裂纹型式转变为复杂的多裂纹型式，且裂纹宽度急剧增加，损伤破坏扩展至整个受拉区.
： To deal with the interface damage of non-ballasted tracks, the coordinated working performance of double-layer concrete was studied. From the mesoscopic perspective, actual aggregate distribution was obtained using the image processing technology, and the 2D model of double-layer concrete was established to simulate and validate the four-point flexural test. The influences of the loading strain rate on the flexural failure mode, the flexural-tensile strength and the macroscopic relationship of stress and displacement were explored. Results show that the simulated stress-displacement curve and failure mode are similar with the tested ones, which means that using the mesoscopic model to simulate the progress of crack propagation is feasible. Under the high loading strain rates of 1×10-2 /s and 1×10-1 /s, large damage occurs at the interface of double-layer concrete. When the loading strain rates are 1×10-3/s, 1×10-2/s,and 1×10-1 /s, respectively, the maximum bearing stress are 1.50, 6.41,and 14.40 MPa, respectively. The single crack propagates along the weak interface and transfers to the complicated multi cracks. Moreover, the crack width increases greatly and the concrete damage expands to the whole tension area