下承式哑铃型钢管混凝土系杆拱桥静力性能研究

Mechanical Performance of Dumbbell-shaped Concrete-filled Steel Tubular Tied Arch Bridge

目的研究下承式哑铃型钢管混凝土系杆拱桥在施工过程中的应力与变形,为实际工程应用提供理论依据。方法采用有限元软件Midas/Civil建立钢管混凝土系杆拱桥有限元模型,分析拱桥施工过程中应力、变形的变化规律及结构参数变化对拱肋受力的影响。结果钢管与混凝土峰值压应力均位于拱脚截面,考虑收缩徐变影响时拱脚上弦管压应力较二期荷载作用下提高61%;与先浇筑上管混凝土相比,先浇筑哑铃型下管混凝土时,组合截面中性轴下移且应力变化幅度较小;拱肋含钢率介于4%~9%时,增大钢管壁厚与直径可使拱脚截面、1/4截面、跨中截面峰值压应力、峰值挠度降低;拱肋内倾角为0°~13°时,拱肋截面峰值挠度随内倾角的增大呈现先减后增趋势,其中内倾角为7°时挠度最小。结论考虑运营期拱肋混凝土收缩徐变时,哑铃型拱肋处于全截面受压状态;对于采用哑铃型截面的下承式钢管混凝土系杆拱桥,先浇筑拱肋下管混凝土可使系杆拱桥体系受力更加合理;内倾角变化对拱肋峰值挠度有一定影响。

In this paper,the stress and deformation of the through dumbbell-shaped concrete filled steel tubular tied arch bridge during construction was studied,to provide theoretical basis for the practical engineering application.The CFST tied arch bridge model was established based on Midas/Civil software,the evolution law of stress and deformation and effect of structural parameters on force of arch rib during the construction stage of arch bridge was evaluated.It is found that the peak compressive stress of steel tube and concrete located within the arch foot section,and the compressive stress of the upper chord of the arch foot can be increased by 61%compared with the second stage load considering the influence of shrinkage and creep stage;Compared with the first casting upper pipe concrete,the neutral axis of the composite section moves downward and the stress variation is smaller;The method of increasing the wall thickness and diameter of steel pipe can be used to reduce the peak compressive stress and peak deflection of arch foot section,1/4 section and mid-span section when the steel content of arch rib is between 4%and 9%;The peak deflection of arch rib section decreases first and then increases with the increase of the inclination angle when the inclination angle of arch rib is 0°~13°,and the deflection reaches the minimum value when the inclination angle is 7°.Meanwhile,considering long-term shrinkage and creep effects of the arch rib concrete,the whole cross-section of the arch rib is under compression state;As for CFST arch bridge with dumbbell-shaped section,first casting concrete of the dumbbell-shaped lower pipe is more feasible to obtain stable structures;The change of inclination angle has certain influence on the peak deflection of arch rib.