Design of Half-Through Cable-Arch Bridge with 700 m Main Span
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摘要:随着拱桥跨径的增加，拱肋稳定性问题突出，且巨大的推力需通过系杆或基础平衡，大跨度悬索桥的庞大锚碇耗资巨大. 针对这两个问题，结合拱和缆索的受力特点，提出一种新的桥梁结构体系——中承式缆拱桥. 首先，在主跨和边跨均加入拱圈；其次，去掉悬索桥锚碇，将主缆锚固于边拱拱脚；最后，通过选取适宜的垂跨比、矢跨比及拱轴系数，保证结构在恒载作用下主缆张力、主拱推力、边拱推力在数值上基本相等，从而使结构处于无推力状态并达到改善结构力学性能的目的. 给出了新型桥的具体结构形式和受力机理，并以700 m跨径为例对其进行设计研究，对其施工过程提出了设想. 有限元计算分析表明：中承式缆拱桥的拱与缆索共同承担桥面荷载，与同条件下的连续拱桥相比，其强度承载力提高约25%，稳定承载力提高约70%，同时恒载作用下结构产生的水平力基本为0，为突破拱桥跨径奠定了坚实的基础.Abstract:As the span of arch bridges increases, the stability problem of the arch rib is becoming severe and the huge horizontal thrust needs to be balanced with tie rods or foundation; meanwhile, large anchors of a long-span suspension bridge costs a lot. Aiming at the two problems above, a new type of bridge structure, half-through cable-arch bridge, was proposed based on mechanical properties of arches and cables. The specific structure and force mechanism of this new type bridge are elaborated. First, arch rings are added to both the main span and side span of a suspension bridge. Then, its anchors are removed and main cables are anchored to the side arch feet. Finally, by choosing appropriate parameters such as sag-to-span ratio, rise-to-span ratio and arch-axis coefficient, the tension of main cable, the thrust of main arch and the thrust of side arch can be basically equal in value under dead load, so that the structure is in a state of no thrust and thus structural mechanical properties can be improved. Taking a half-through cable-arch bridge with a 700 m main span as an example, the design of its structural layout and components are described in details and a sequence of construction steps is suggested. Finite element analysis shows that the arch and cable of half-through cable-arch bridge share the load of bridge deck; compared with the continuous arch bridge under the same conditions, the half-through cable-arch bridge can increase the strength bearing by nearly 25% and increase the stable bearing capacity nearly by 70%. In addition, the horizontal force generated by the structure is nearly zero under dead load, which lays a solid foundation for breaking through the span limit of arch bridges.
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Key words:
- half-through/
- cable-arch bridge/
- arch bridge/
- suspension bridge/
- hybrid bridge
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图 4700 m级中承式缆拱桥结构布置（单位：m）
Figure 4.Structural layout of the half-through cable arch bridge with a 700 m main span (unit：m)
表 1组合一主拱应力
Table 1.Stress of main arch under the first load combination
类型 主缆承担
荷载比例/%主拱拱脚
最大应力/MPa主拱拱顶
最大应力/MPa连续拱桥 100 149.98 149.90 700 m 中承
式缆拱桥47 112.17 111.07 变化率/% 25.2 25.9 
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表 2组合二主拱应力
Table 2.Stress of main arch under the second load combination
类型 主缆承担
荷载比例/%主拱拱脚
最大应力/MPa主拱拱顶
最大应力/MPa连续拱桥 100 173.20 174.39 700 m 中承
式缆拱桥45 108.74 133.20 变化率/% 37.3 23.6 下载:
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表 3结构位移
Table 3.Structural displacement
类型 塔顶水平
位移/mm主拱竖向
位移/mm主跨最大
挠度/mm连续拱桥 8.24 122.29 237.91 700 m 中承
式缆拱桥108.68 273.27 变化率/% 11.1 14.9 下载:
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表 4组合三及组合四主拱应力
Table 4.Stress of main arch under the third and fourth load combination
类型 升温 25 ℃ 降温 25 ℃ 不均匀沉降 拱脚最大应力/MPa 拱顶最大应力/MPa 拱脚最大应力/MPa 拱顶最大应力/MPa 拱脚最大应力/MPa 拱顶最大应力/MPa 连续拱桥 134.82 139.78 170.78 160.02 181.80 162.10 700 m 中承
式缆拱桥103.71 106.12 126.28 115.43 145.10 127.60 变化率/% 23.1 24.1 26.1 27.9 20.2 21.3 下载:
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表 5组合五主拱应力
Table 5.Stress of main arch under the fifth load combination
升温 25 ℃ 降温 25 ℃ 拱脚最大应力/MPa 拱顶最大应力/MPa 拱脚最大应力/MPa 拱顶最大应力/MPa 连续拱桥 179.17 184.92 198.79 132.12 中承式缆拱桥 118.93 146.66 192.79 152.47 变化率/% 33.6 20.7 33.5 20.9 下载:
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表 6屈曲分析结果
Table 6.Results of buckling analysis
类型 连续拱桥 中承式缆拱桥 稳定系数变化率/% 临界荷载系数 稳定系数 临界荷载系数 稳定系数 第1模态 58 4.20 81 7.45 77.38 下载:
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表 7不同垂跨比的计算结果
Table 7.Calculation results for different sag-span ratios
矢跨比 垂跨比 主缆承担
荷载比例/%主拱最大
应力/MPa稳定系数 1/6 1/14 45.00 133.00 7.45 1/12 50.88 128.14 10.30 1/10 58.43 122.19 13.50 下载:
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