桥上CRTSⅠ型双块式无砟轨道早期开裂行为研究

Investigation on Early Cracking Behavior of CRTSⅠDouble-block Ballastless Track on Bridge

以桥上CRTSⅠ型双块式无砟轨道为研究对象,基于混凝土早期性能发展基本理论,利用Ansys建立三维温度场与应力场分析模型,考虑养护方法、拆模龄期、拆模温度与钢筋直径等参数影响,对双块式无砟轨道早期开裂行为进行数值模拟。结果表明:无砟道床不同位置处混凝土主拉应力整体呈循环上升趋势;拆模前后混凝土应力时程曲线波动程度差异较大,拆模后4 h内道床混凝土主拉应力时程曲线出现明显增长。合理选用养护方式可有效降低道床板早期开裂风险;伴随着拆模龄期的延长与拆模温度的升高,拆模后无砟道床4 h内温度改变量与道床混凝土开裂风险均呈降低趋势;相同配筋率下,减小钢筋直径可降低桥上CRTSⅠ型双块式无砟轨道早期开裂风险。

Based on the basic theory of early performance development of concrete,Ansys was used to develop a 3D temperature field and stress field analysis model of the CRTSⅠdouble-block ballastless track on bridge.The early cracking behavior of the double-block ballastless track was numerically simulated,considering the effects of the factors including curing method,demolding age,demolding temperature and the diameter of the steel bar.The results show that the development of the principal tensile stress of concrete at different positions of the track bed presents a cyclic upward trend in general.Before and after demolding,the fluctuation degree of the concrete stress-time history curve is quite different,with the principal tensile stress of the track bed concrete increasing significantly within 4 hours after demolding.An appropriate curing method can reduce the early cracking risk effectively.With the increase of the demolding age and the demolding temperature,the temperature fluctuation and the risk of cracking of the track bed both show a decreasing trend.Under the same reinforcement ratio,reducing the steel bar diameter can reduce the risk of early cracking of the CRTS I double-block ballastless track on bridge.