钢箱混凝土索塔竖转过程的受力分析

Analysis on Mechanical Behavior of Steel-box Concrete Cable-pylon during Vertical Swivel

作为一种无支架施工方法,钢箱混凝土索塔竖转施工具有不需高空拼装、结构整体性好、转体精度控制高等优势。但是,索塔竖转过程受力复杂,钢箱、混凝土及其界面的应力变化特点尚不明确。采用几何学进行钢箱混凝土索塔运动轨迹的离散化分析,建立竖转过程的力学简化模型,得到竖转过程索塔的内力变化规律,并以某索塔为例,采用数值模拟方法进行了索塔竖转过程钢、混凝土的轴向应力分析及钢混界面剪切应力分析。结果表明,索塔整体竖转过程中,顶底板轴向应力与界面剪切应力较大,腹板受力变化不明显;轴向应力最不利位置位于竖向提升力与桥塔高度的1/3附近,剪切应力在转铰支承与竖向提升力附近5 m内应力集中;应力集中范围与轴力、弯矩大小无关,此处宜设置PBL连接件,保证钢混界面黏结良好。

As a non-support construction method, the vertical swivel of steel-box concrete cable-pylons has the advantages of no need for high altitude assembly, good structural integrity and high precision control of swivel. The force during the vertical rotation of the cable tower is complex, and the stress change characteristics of the steel box, concrete and their interfaces are not yet clear. In this paper, geometry is used to discretize the movement track of steel-box concrete cable-pylon, and the simplified mechanical model of vertical swivel process is established, and the variation law of internal force of the cable-pylon is obtained. Taking a cable-pylon as an example, the axial stress analysis of steel and concrete and the interfacial shear stress analysis of steel-concrete interface during vertical swivel of the cable-pylon are carried out by using the numerical simulation method. The results show that the axial stress and interfacial shear stress of the roof and floor are larger, while the stress of the web is not obviously changed during the whole vertical swivel of the cable-pylon. The most disadvantageous position of the axial stress is located near the vertical lifting place and 1/3 of the height of the cable-pylon, and the shear stress concentration phenomenon is most obvious in the range of 5m around the ball hinge support and the vertical lifting force. The range of stress concentration is not related to the axial force and bending moment. PBL connector should be set here to ensure good bonding of steel-concrete interface.