中文摘要：

鱼骨单主梁模型是分析大跨度钢桁梁悬索桥抗风性能的常用简化模型．针对由于悬索桥钢桁梁断面杆件众多造成的其扭转质量惯性矩计算繁琐、精度低的问题，提出一种基于均匀附加扭转质量惯性矩前后结构扭转频率的变化计算钢桁梁扭转质量惯性矩的方法，并给出了该方法的理论说明、适用条件等．以一钢桁梁悬臂结构为例进行了数值仿真，结果表明：附加扭转质量惯性矩施加在全截面或上、下弦杆节点，且钢桁梁的长细比L／D≥20时，该方法计算的扭转质量惯性矩有较高的精度．采用该方法计算了多座钢桁梁悬索桥的主梁扭转质量惯性矩，比较了全桁架模型和单主梁模型扭转振动频率，验证了方法的有效性．

英文摘要：

The simplified ＂fish-bone＂ model is commonly employed for the analysis of wind-induced responses of truss-stiffened suspension bridges, and one key step in establishing such a model is the calculation of the mass moment of inertia for the stiffening truss. Due to numerous members in a stiffening truss section, the calculation process of the moment of inertia is usually complicated and imprecise. Therefore, a new method is proposed based on the change in torsional frequencies of a cantilever truss girder caused by attaching the additional mass moment of inertia on the truss nodes, where the theoretical background is given, and the applicable conditions are also investigated. By taking a cantilever truss girder as an example, numerical simulation results show that the proposed method provides the best accuracy when the known mass moment of inertia is uniformly applied to all section nodes or to the nodes of chord joints, and the slenderness ratio of truss girder exceeds 20. Finally, the mass moments of inertia of stiffening truss are ob- tained by the proposed method, and are then used to establish the simplified ＂fish-bone＂ models for several selected suspension bridges. The torsional frequencies obtained by the simplified ＂fish-bone＂ models agree well with those predicted by their detailed models, which validates the effectiveness of this simplified method.