大跨度钢箱桁组合连续梁桥涡振性能研究

主梁的大幅涡振一直是困扰跨海连续梁桥的主要病害之一，但对箱桁组合断面主梁的涡振研究较少。拟建的澳氹第四跨海大桥为一座变截面非对称钢箱桁组合连续梁桥，主梁宽度近50 m，且桥面附属结构呈非对称分布，气动外形极为复杂。该文采用1∶70缩尺比的跨中主梁断面节段模型风洞试验研究了澳氹四桥的涡振性能，对比分析了风攻角、紊流度、桥梁阻尼比、附属结构气动外形等因素对主梁断面涡振性能的影响。并通过将外侧栏杆、电缆箱、供水管、风障及防撞栏杆等桥面附属结构拆解，探讨了主梁涡振的原因。进一步比较了中跨跨中(L/2)及三分之一跨(L/3)两种不同断面的涡振性能差异。研究表明：宽幅钢箱桁组合梁断面容易在负攻角下发生大幅涡振，且不同位置两种断面涡振性能差异显著，高耸桁架的遮挡效应对该类桥梁涡脱特性影响较大；非对称横断面形式对涡振性能影响较大，减小外侧栏杆透风率以及采用布置位置合理的下扰流板可有效减小涡振幅值。基于风洞试验数据识别了涡振尾流振子模型的气动参数，准确重现了涡振幅值-风速关系曲线。

VORTEX-INDUCED VIBRATIONS OF LONG-SPAN CONTINUOUS BRIDGES WITH STEEL TRUSS-STIFFENED BOX-GIRDER

Vortex-induced vibrations (VIVs) are one of the most critical issues for continuous beam bridges with long spans. The proposed 4th Bridge at Macao is a continuous-beam bridge made of steel truss-stiffened box girders with variable height and asymmetric configuration, and the bridge girder has a width of approximately 50 m and complex aerodynamic shape owing to various accessory components. The VIV performance of the 4th Bridge at Macao is studied by wind tunnel tests on 1∶70 sectional models, and the effects of wind attack angles, turbulence intensity, structural damping, wind barrier are compared. Two typical cross sections at the L/2 and L/3 of the main span are tested. The results shown that the cross-section of truss-stiffened box-girder may generate VIVs under negative wind attack angle, and the VIV of two cross-sections at negative attack angles are different, implying the effect of truss on VIV is significant. The results also shown that the asymmetry of the cross-section may significantly affect the VIV performance of the continuous beam bridge with steel truss and variable cross-sections. The amplitude of the VIV response can be reduced effectively by lowering the permeability of the outer barrier and adopting a spoiler with a reasonable placement. Finally, the parameters of the wake oscillation model for the simulation of vortex-induced vibrations are identified based on the experimental results, which can accurately reflect the relation between the amplitude of VIV and the wind speed.