为研究分体三箱断面主梁桥梁的抗风性能并提出有效的气动优化措施，基于某公铁两用分体三箱断面主梁大跨度斜拉悬索协作体系桥梁，开展了不同风攻角、不同紊流度流场以及5种不同气动措施下的节段模型风洞试验。结果表明,箱体分离会使主梁断面颤振临界风速大幅提高，但会造成箱体间流场的复杂化从而带来涡激振动（VIV)问题。成桥状态原始断面0°、±3°攻角下均发现了扭转VIV，最大扭转振幅1238°；颤振临界风速均高于973 m/s。桥面抑流板、不同检修轨道位置及梁底导流板3种措施对扭转VIV抑制效果不理想；箱体间隙处加装均布纵向格栅可有效抑制扭转VIV，且透风率越小优化效果越明显，但透风率小于23%的格栅会造成颤振临界风速的下降；10%透风率格栅与下中央稳定板组合措施在完全抑制扭转VIV的同时保证了桥梁的颤振性能。基于计算流体动力学(CFD)，得到了原始断面和优化工况主梁周围的流场结构及气动力变化规律。箱体间距处与下游公路箱上方大尺度旋涡的形成是主梁VIV的主要诱因。优化后断面箱体间距处大尺度旋涡被打散，升力和扭矩时程均方根（RMS)明显减小，从而有效改善了主梁的VIV性能。同时优化工况的升力和力矩系数曲线的斜率在±5°攻角范围内均为正值，说明主梁具备了气动稳定必要条件。

Here, to study wind-resistance performance of a split 3-box section main girder bridge and propose effective aerodynamic optimization measures, based on a long-span cable-stayed suspension bridge with split 3-box section main girder for the road-rail dual purpose, wind tunnel tests for segment models were conducted under different wind attack angles, different turbulence flow fields and five different aerodynamic measures. The results showed that box separation can greatly increase the flutter critical wind speed of main girder section, but this situation can complicate the flow field among 3 boxes to cause vortex-induced vibration (VIV); under conditions of the original section in completed bridge state with attack angles of 0° and ±3°, torsional VIV appears with the maximum torsional amplitude of 1.238°; in general, the flutter critical wind speed is higher than 97.3 m/s; the effects of three measures of bridge deck flow restrictor, different maintenance track positions and beam bottom flow deflector are not ideal for torsional VIV suppression; the longitudinal grid with uniform distribution at gap of boxes can effectively suppress torsional VIV, the smaller the air permeability, the more obvious the optimization effect; the grid with air permeability less than 23% can cause decrease in the flutter critical wind speed; the combination measure of grid with 10% air permeability and lower central stabilizer plate can completely suppress torsional VIV and ensure bridge flutter performance; based on the computational fluid dynamics (CFD), the flow field structure and aerodynamic force variation law around the original section and main girder with optimized conditions are obtained; the main cause of main girder’s VIV is the formation of large-scale vortices at gaps among boxes and above downstream highway box; after optimization, large-scale vortices are scattered at gaps among boxes, and root mean squares of lift force and torque time histories are obviously reduced to effectively improve VIV performance of main girder; at the same time, both slopes of lift force and torque coefficient curves under the optimized conditions are positive within the attack angle range of -5°—5°, so main girder has necessary conditions for aerodynamic stability.