道床阻力区域分布及退化对钢轨纵向力的影响

摘要

为深入探索有砟道床阻力演变对桥上无缝线路力学行为的影响,针对路基地段与桥上道床纵、横向阻力开展试验研究.以一座铁路常用双线特大连续梁桥为例,获得了桥上线路阻力分布特征,并提出实际道床在服役过程中存在局部阻力退化现象.在此基础上,建立了可考虑道床阻力非均匀分布与退化效应的桥上无缝线路纵向力学行为分析模型,开展了道床阻力分布及退化对大跨桥上无缝线路力学行为的影响分析.研究结果表明:桥上道床纵向阻力区域分布差异显著,桥跨中部纵向阻力值最大,阻力值为31.8 kN/枕,梁缝附近道床纵向阻力相对较小,阻力值为21.7 kN/枕,阻力退化效应明显;桥上道床横向阻力分布同样表现出一定区域分布特征,但退化效应并不明显,桥跨中部与梁缝处阻力值分别为31.7、25.5 kN/枕;由于受到温度荷载作用下梁体伸缩、列车动荷载作用下桥梁产生振动变位和梁端转角的影响,散休道床始终处于拉伸压缩的动态变化过程中,道床阻力表现出明显的退化特性;考虑道床阻力退化效应时,温度荷载作用下的钢轨伸缩附加力、钢轨位移、梁轨相对位移值有一定衰减,当桥梁温度跨度为140 m时,钢轨纵向附加力最大值减小约11.7％,且衰减率随着温度跨度的增加近似呈线性增长,按现有规范计算方法得到的梁轨相互作用结果偏大.%In order to explore the effect of ballast resistance evolution on the mechanical behavior of the continuously welded rail (CWR) on bridge,tests were conducted for the longitudinal and lateral ballast resistances on bridge and roadbed sections.Taking an example of an extra-large double-line continuous beam bridge commonly used in railway,the track resistance distribution characteristics on bridge were obtained,and the local ballast resistance degradation was discovered in the ballast service.On this basis,the longitudinal mechanics behavior model of CWR on bridge was established,which takes into account the non-uniform distribution and degradation of ballast resistance.The results show that the distribution of ballast longitudinal resistance on bridge shows significant regional distribution characteristics,the maximum longitudinal resistance was 31.8 kN per sleeper at the central span of bridge,and the longitudinal resistance near the beam joint was relatively small,21.7 kN per sleeper,demonstrating obvious ballast resistance degradation.The lateral resistance distribution on bridge also has moderate regional distribution characteristics,the lateral resistance at the central span of bridge was 31.7 kN per sleeper and the lateral resistance near the beam joint was 25.5 kN per sleeper,while the degradation does not obvious.As thermal load leads to beam expansions and the dynamic loads of trains cause bridge vibration displacement and rotation angles at the beam support,the crushed-stone ballast dynamically changes between tension and compression,and the ballast resistance shows obvious degradation characteristics.When there is ballast resistance degradation,the rail longitudinal force,rail displacement and relative displacement between bridge and track under thermal loading has a certain attenuation.Thus,the maximum rail longitudinal additional force with the temperature span of 140 m was reduced by about 11.7％,and the attenuation rate increases linearly with the increase of temperature span.The beam-rail interaction is relatively large if it is calculated according to specifications.