既有重载铁路32 m预应力混凝土T梁斜截面疲劳作用分析

Fatigue Action Analysis on Inclined Section of 32 m Prestressed Concrete T⁃girder of Existing Heavy Haul Railway

既有重载铁路混凝土桥梁结构的病害日益显现,后张法预应力混凝土简支T梁腹板大量出现斜裂缝。以大秦铁路跨度32 m预应力混凝土T梁为研究对象,分析典型截面在重载列车移动荷载作用下的内力变化特征以及运营荷载作用下的主应力变化特征。研究结果表明:重载列车移动荷载对梁体的疲劳作用特征表现为每通过1整列车、1节货车、1个轮轴,梁体分别经历1次大、中、小幅度的主应力循环,且主应力的周期性变化特征与剪力相同;重载铁路典型32 m简支梁的主拉应力已接近甚至超过规范限值,且疲劳作用次数为普通货运铁路的数倍,主应力循环作用产生的疲劳累积损伤过大、斜截面疲劳抗裂性能相对不足可能是32 m简支梁腹板斜裂缝的主要成因。研究结果可为既有重载铁路混凝土梁斜截面疲劳抗裂机理的深入研究提供理论依据。

The deterioration of concrete bridge structure of existing heavy haul railway is becoming more and more serious.A large number of inclined cracks appear in the web of 32 m post-tensioned prestressed concrete T-girder.In this paper,the research object is the 32 m prestressed concrete T-girder used in Datong-Qinhuangdao Railway.The feature of typical section internal force variation under moving load action of heavy haul train and the feature of typical section principal stress variation under operation load were studied.The results show the characteristics of fatigue action on the girder under the moving load of heavy haul train.Every time a whole train,a freight car and an axle passes through the girder,the girder will experience a large,a medium and a small amplitude of principal stress cycle,and the periodic variation characteristics of principal stress are the same as shear force.The principal tensile stress of the typical 32 m simply supported girder of heavy haul railway has approached to or exceeded the limit value of the code,and the fatigue action are several times of that of ordinary freight railway,excessive fatigue cumulative damage caused by principal stress cycles and the relative deficiency in the fatigue cracking resistance of inclined section might be the main cause of inclined cracks in the web of 32 m simply supported girder.The research may provide a theoretical basis for the in-depth study of fatigue crack resistance mechanism of inclined section of existing heavy haul railway concrete girders.