考虑径向湿度梯度约束环形试验开裂过程研究

Investigation on Fracture Process of Restrained Ring test Considering Moisture Gradient

对于实际工程中的平板式混凝土结构,例如混凝土路面、桥面板等,收缩裂缝随处可见。针对美国试验材料学会(ASTM)推荐的约束环形试验,采用试验与数值相结合的方法研究了考虑径向湿度梯度混凝土环的开裂过程。通过引入虚拟温度场模拟混凝土的收缩过程,结合虚拟裂缝模型和基于起裂韧度的裂缝扩展准则研究了混凝土环裂缝起裂与扩展全过程,并且定量分析了裂缝扩展过程中钢环约束与自身约束的关系。根据试验与数值结果可知,考虑径向湿度梯度的影响,混凝土环截面最大拉应力始终出现在试件外环即干燥面处,试件开裂时裂缝从外侧起裂并且由外侧向内侧扩展。由于裂缝失稳,起裂当天可以观察到,裂缝贯穿整个截面。构件失稳破坏的标志是钢环压应变出现滞回。驱动试件开裂的约束作用中,钢环约束占主要作用,裂缝扩展过程中钢环约束作用不断增强。

As for the restrained ring test recommended by American Society for Testing Material(ASTM),experiment and numerical analysis were conducted to explore the fracture process considering the radial moisture gradient.The shrinkage effect of concrete is simulated by the fictitious temperature field,and the crack initiation and propagation process is studied by introducing the fictitious crack model and initial fracture toughness-based crack propagation criterion.The relation between steel ring restraint and self-restraint in crack propagation process is quantitatively analyzed.According to experimental and numerical results,when considering the radial moisture gradient,the maximum tensile occurs at outer surface of cross section all the time and crack initiates at outer surface and propagate into inner surface.After initiating,the crack propagates unstably,and the sudden drop of steel ring strain means the structural damage of concrete ring.The steel ring restraint plays a leading role in driving the concrete to crack and increases in crack propagation process.