西溪河大桥主桥疲劳性能分析及寿命预测

Fatigue Behavior Analysis and Life Prediction of Main Bridge of Xixi River Bridge

随着我国高速铁路网络的逐步形成,钢结构铁路桥梁的疲劳问题日益显著,成为研究的热点。以典型的上承式钢拱桥——西溪河大桥为研究对象,通过有限元软件ANSYS对主桥结构建立数值模型,分析其在疲劳荷载下的应力分布及应力集中系数。对材料的基本S^N曲线进行合理修正,得到针对桥梁构件的S^N曲线;应用名义应力法,计算桥梁结构中各杆件的疲劳寿命,进而研究大桥的疲劳性能。研究结果表明:西溪河大桥的疲劳寿命大于107次,疲劳性能满足实际要求;应力集中主要出现在腹杆与弦杆的焊接部位,因而施工时应重点保证焊接质量;虽然疲劳破坏为脆性破坏,但拱桁架中部分杆件失效后可进行多次应力重分布,结构仍然有一定的静力及疲劳承载能力,因此结构的整体疲劳破坏具有一定延性。文中提出的疲劳寿命计算方法适用于桥梁的寿命评估。

With the rapid development of high speed railway, the fatigue behavior of the steel railway bridge has become an important research topic. Based on the steel braced deck-type arch bridge Xixi River Bridge, numerical model of main bridge was established by finite element software ANSYS to ana- lyze the stress distribution and stress concentration factor of bridge under fatigue load. Reasonable correct- ing of SuN curves of steel material was conducted to obtain the S＇--N curves of members in the bridge. According to the nominal stress method, the fatigue lives of members in the bridge were calculated to ana- lyze the fatigue behavior of the whole bridge. The results show that the fatigue life of Xixi River Bridge is over 107, which meets the design requirements. Stress concentration appears at the weld between web and chord members, so the welding quality should be assured during the construction. Although the fatigue failure is brittle, the partial member of arch truss will do multiple stress redistribution after failure, which still leads to certain static and fatigue bearing capacity and ductile failure. Hence ,the proposed fatigue life calculation method can be used for the evaluation of bridge life.