地震作用对有砟轨道桥上无缝道岔纵向受力与变形影响分析

桥上无缝道岔是在高速铁路、艰险山区铁路上铺设跨区间无缝线路不可避免的技术难题,同时跨越震区时,道岔结构自身处于双层薄弱环节之中。根据地震作用下有砟轨道桥上无缝道岔梁轨相互作用原理,建立地震作用下岔-桥-墩动力非线性有限元模型,分析地震波频谱特性、地震动加速度峰值、岔区阻力、梁体温差等因素下的有砟轨道桥上无缝道岔地震作用响应规律。研究结果表明:无缝道岔约束作用较大提高了桥梁结构的低阶自振频率,而且改变了其振动形态;地震波频谱特性和加速度峰值大小对桥上无缝道岔响应影响显著,地震荷载波频越靠近结构主频,加速度峰值越大,桥上无缝道岔受力和变形越大;在钢轨温变较高,又同时考虑地震荷载效应时,钢轨强度和线路稳定性均得不到保障,建议对跨越震区的桥上无缝道岔设计时检算地震荷载与钢轨、梁体温变共同作用时的钢轨纵向力以及道岔联结件受力、关键位置相对位移等。

Seismic Impacts on Longitudinal Stress and Distortion of Welded Turnout on Bridge

Laying welded turnout on bridges of high-speed railway or in dangerous mountain areas is an inevitable technical challenge. According to beam-turnout interaction principle,a dynamic nonlinear finite element model of turnout-bridge-pier in ballasted track is built to analyze the response mechanism of the welded turnout on ballasted bridge subject to the impacts of seismic wave spectrum characteristics,seismic acceleration peak,turnout area resistance and beam temperature differences. The results show that bridge vibration mode is changed after application of welded turnout and the low order mode frequency is considerably increased; both seismic wave spectrum characteristics and seismic acceleration peak impose great influence on the responses of welded turnout constraint; the closer the seismic frequency to structural basic frequency and higher the wave amplitude,the larger the stress and distortion of welded turnout; rail strength and track stability cannot be guaranteed under the synthetic effect of seismic load and severe temperature condition. It is suggested that the design of welded turnout on bridges in earthquake zones should take into consideration of the rail longitudinal strength,turnout connector stress and relative displacement at key positions under the combined action of seismic load and temperature changes of rail and beam.