基于能量原理的板桁结合型加劲梁连续化分析方法

Continuous Analysis Method for Deck-truss Composite Stiffening Girder Based on Energy Principle

针对大跨径板桁结合型加劲梁悬索桥精细有限元模型单元数量多、计算效率低的特点,基于能量原理推导了板桁结合型加劲梁主桁架腹杆和下平联的连续化等效板厚计算公式,根据板桁结合型加劲梁的弯曲与扭转受力特点分别构造了相应的连续化等效截面,并采用悬臂梁模型验证等效截面的合理性,最后以主跨跨径1 480m的岳阳洞庭湖大桥为研究对象,将连续化分析方法与精细有限元法的位移与应力计算结果进行了比较。结果表明:采用2种方法计算得到的加劲梁位移的结果吻合较好,最大相对误差不超过4%;移动荷载作用时,采用连续化分析方法计算得到的上弦杆压应力受桥面板剪力滞效应的影响,导致其压应力的相对误差较下弦杆大,但上弦杆压应力的绝对差值不超过5.0MPa;横桥向静风荷载作用下,采用连续化分析方法计算得到的弦杆应力相对误差不超过5%;连续化分析方法的计算精度能满足要求,计算效率较精细有限元法大幅提高。

Aimed at the characteristics of high precision finite element model with many elements and low computational efficiency for long-span suspension bridge with deck-truss composite stiffening girder, the calculation formulas for continuous equivalent plate thickness of the main truss web members and bottom bracing were derived based on energy principle. The continuous equivalent sections of deck-truss composite stiffening girder were correspondently constructed according to the mechanical characteristics of bending and torsion, and the rationality of the equivalent sections was proved through cantilever girder model. The calculation results of continuous analysis method （CAM） and high precision finite element method （HPFEM） were compared by taking Yueyang Dongting Lake Suspension Bridge with a span of 1 480 m as the object. The results show that the calculation results of displacement with CAM agree well with the results obtained with HPFEM, of which the maximum difference is less than 4%. By using CAM, when moving load is applied, the deviation of compression stress in upper chords is higher than that in bottom chords under the impact of shear lag of the deck plate, but the highest difference is below 5.0 MPa. Under static wind load, the relative stress difference in chords is less than 5%. Computational efficiency is greatly improved by CAM compared with HPFEM, and its precision meets the requirement.