四千米级悬索桥新型结构体系研究

New Structure System for 4000 m Class Suspension Bridge

悬索桥是目前跨越能力最大的桥型。随着跨径的进一步增大,其结构动力刚度将不断下降,导致结构抗风能力降低。研发满足结构受力以及抗风稳定性要求的加劲梁断面形式和新型悬索桥结构体系是四千米级悬索桥设计和建造的关键控制因素。为此,首先对采用层流抑振风嘴(V形风嘴、Y形风嘴)和新型紊流制振风嘴的钢箱梁断面开展了节段模型风洞试验,探讨了常规平面缆悬索桥的极限跨径;通过建立全桥三维杆系有限元模型,计算总结了结构扭转基频随跨径的变化规律,并研究了主缆矢跨比、主缆空间化、设置抗扭辅助索等措施对结构扭频的提升效果,提出推荐的新型悬索桥结构体系;最后基于已有结论对四千米级悬索桥进行概念设计。研究结果表明:根据“紊流制振”理论设计的新型加劲梁断面,在保证颤振检验风速80 m·s^(-1)以上时可以使常规悬索桥跨径达到2700 m;通过在主缆间设置抗扭索是一种较容易实现的提升大跨度悬索桥动力刚度的措施,此举可以使结构扭频提高47.5%;采用紊流制振风嘴钢箱梁断面及新型悬索桥结构体系的悬索桥,在保证颤振临界风速80 m·s^(-1)的情况下主跨跨径可达4000 m;通过增加抗风缆等结构措施,可以使悬索桥跨径进一步提高至6000 m,这些优化措施为未来建造更大跨度的跨海桥梁工程提供了可能性。

Of the various types of bridges,suspension bridges have the largest span capacity.With a continuous increase in the span,the dynamic rigidity of the structure decreases,leading to a reduction in the wind resistance of the structure.In this study,the development of the beam section type and the proposal of a structure system meeting the requirements for structural stress and wind resistance stability were used as the key control factors for the design and construction of a 4 km suspension bridge.First,a section model wind tunnel test was conducted for a steel box girder section with a laminar flow damper(V-shaped damper,Y-shaped damper)and new turbulence damper;in addition,the ultimate span of a conventional plane cable suspension bridge was discussed.By building a three-dimensional finite element model,the variation characteristics of the structural torsional base frequency with the span were calculated and summarized.The influences of the sag ratio of the main cable,main cable spatialization,and setting of the torsional auxiliary cables were studied.Correspondingly,a new suspension bridge structure system was proposed.Based on the conclusions,the conceptual design of the 4 km suspension bridge was conducted.The results show that the span of a conventional suspension bridge can reach 2700 m when the wind speed in the flutter inspection exceeds 80 m·s^(-1) at the new stiffening beam section.The dynamic stiffness of a long-span suspension bridge can be easily improved by setting torsional cables between the main cables;this can increase the torsional frequency of the structure by 47.5%.The main span of a suspension bridge with the turbulent vibration control theory and new suspension bridge structure system can reach 4000 m with an 80 m·s^(-1) critical wind speed for the flutter.The span of a suspension bridge can be further increased to 6000 m by adding structural measures such as wind-resistant cables,providing the possibility to construct a larger span cross-sea project in the future.