负弯矩作用下钢混凝土结合梁性能研究

Behavior of Steel-Concrete Composite Beams under the Action of Negative Moment

芜湖公铁两用长江大桥系双层 ,上层为公路桥 ,下层为双线铁路桥。为了使上层公路桥面板能帮助主桁上弦杆抵抗巨大的纵向压力 ,正桥全部采用混凝土桥面板与钢桁梁共同作用的板桁结合梁。但是 ,在主桥边跨各连中间墩附近的上层混凝土板却处于受拉状态。为了给芜湖桥受拉区板桁结合梁提供合理的结构形式和设计依据 ,本研究制作了 4根大尺寸结合梁。它们的尺寸、钢构件相同 ,但混凝土板及连接件的数目与布置不同。其中两根梁的混凝土板为全部工地现浇高配筋混凝土 ,另两根为预应力预制混凝土板 +工地后浇微膨胀混凝土。在负弯矩作用下 ,每梁先做 2 0 0万次疲劳试验 ,再做极限承载力试验 ,对结合梁的疲劳性能、极限状态 ,包括刚度、应变、混凝土板中的裂纹等作了对比研究。研究成果已应用于芜湖桥受拉区结合梁的设计。

Wuhu Yangtze River bridge (WYRB) has two layers. The top one is a highway and the bottom one is a double track railway. In order to let the slabs help the top chords of the steel trusses resist the giant compressive forces, slab truss composite structures are used throughout the main bridge. But upon the intermediate piers of the side spans the slabs are in tension. In order to give reasonable structure types and design principles, four large size composite beams are constructed. Their size, steel members are the same. But the concrete and the number of studs are different. Two of them the slabs are cast in site at one time. The other two are precast prestressed slabs plus concrete cast in site. 2×10 6 cycles fatigue test and ultimate load test under the action of hogging moment are conducted on each beam. The behaviors of the beams such as stiffness, strain, cracks of the slabs are studied. The research results of this paper have been used in the design of WYRB.