高铁大跨度斜拉桥主梁钢混结合段力学性能研究

Study on Mechanical Performance of Steel-concrete Composite Segment of Main Girder of Long Span Cable-stayed Railway Bridge

为研究4线高速铁路混合梁斜拉桥新型钢混结合段的力学性能,以主跨672 m的安九铁路鳊鱼洲长江大桥主梁钢混结合段为背景,开展局部缩尺静力和疲劳模型试验,并结合有限元分析钢混结合段的应力分布、滑移开裂及疲劳性能。研究结果表明:最不利工况下,结合段钢构件应力沿横向分布不均且边箱处最大,沿纵向在承压板处产生突变,承压板传力作用显著;最大负弯矩工况下,钢构件的实测应力在1.8倍逐级加载过程中均呈线性变化。钢混间最大滑移仅为0.065 mm,结合段钢混间协同变形良好;挠度结果反映结合段具有良好的刚度并整体呈弹性受力状态;混凝土段顶板于1.4倍最大负弯矩加载时开裂,1.8倍加载下裂缝纵向分布形态表明结合段受力优于钢过渡段。活载最不利工况下,边箱顶板处为主要疲劳敏感区域,钢过渡段水平隔板在疲劳165万次后发生开裂,其余钢结构未开裂;混凝土在疲劳50万次后即开裂,但裂后劣化并不显著;剪力钉和PBL连接件抗疲劳性能良好。钢混结合段具有良好的承载能力及抗疲劳性能,传力合理,可为类似结构提供参考。

To study the mechanical performance of the novel steel-concrete composite segment for the four-track high-speed railway hybrid cable-stayed bridge,the local scaled static and fatigue model tests were conducted for the steel-concrete composite segment of the main girder of the Bianyuzhou Yangtze River Bridge of Anqing—Jiujiang High-speed Railway with a main span of 672 m.The stress distribution,slip cracking and fatigue performance of steel-concrete composite segment were explored with the finite element analysis.The results show that,under the most unfavorable working conditions,the stresses of the steel members in the steel-concrete composite segment are unevenly distributed in the transverse direction,with the maximum stress in the side box girder.Besides,a stress mutation occurs at the bearing plate along the longitudinal direction,illustrating the the significant force transmission effect of the bearing plate.The measured stresses of steel members change linearly with the loading step by step to 1.8 times loading under the maximum negative bending moment.The maximum slip between the steel and concrete is only 0.065 mm,indicating a good coordinating deformation between the steel and concrete in the segment.The deflection results reflect that the segment has a good stiffness and whole segment works elastically.The concrete roof cracks under the 1.4 times loading of the maximum negative bending moment,and the longitudinal distribution of the cracks under the 1.8 times loading shows that the force resistance of the steel-concrete composite segment is better than that of the steel transition section.Under the most unfavorable working conditions of live load,the top plate of the side box is the main fatigue sensitive area.When the fatigue cycle reaches 1.65 million times,fatigue cracking occurs in the horizontal plate in the transition section of the model with the rest of the steel structure remaining uncracked.When the fatigue cycle reaches 500000 times,fatigue cracking occurs in the concrete,but the deterioration after cracking is not significant.The shear studs and PBL connectors have a good fatigue resistance.The steel-concrete composite segment,with good bearing capacity,excellent fatigue resistance and reasonable force transmission,can provide reference for similar structures.