Effect of double-thin-wall distance on seismic response of continuous rigid frame bridge
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摘要: 为了研究桥墩布置形式对连续刚构桥地震响应的影响, 以某弯连续刚构桥为例, 采用通用有限元程序分析了5种不同的双薄壁墩间距对桥梁结构自振频率的影响, 选取桥位场地人工合成地震波, 对其进行了弹性地震响应分析。分析结果表明: 当双薄壁墩间距在主跨径的1/20~1/25之间变化时, 结构基频变化不超过5%, 在地震作用下, 主梁的弯矩、墩底弯矩及主梁位移最大变化不会超过12%, 说明薄壁墩间距对结构自振频率及地震响应的影响不大, 在初步设计阶段或进行弹性地震响应分析时, 如果双薄壁间距在以上范围内变化, 可以不考虑它对结构动力性能的影响。Abstract: In order to study the effect of pier's layout on the seisimic response of continuous rigid frame bridge, a curved rigid frame bridge was taken as an example, the natural frequencies of the bridge under five double-thin-wall distances were analyzed by finite element procedure, and artificial earthquake wave was employed to compute the elastic seismic response of the bridge.The result shows that when double-thin-wall distance lies between 1/20 and 1/25 of main span, the change of fundamental frequency is not more than 5%, and the seismic responses of the moments of girder and pier and the displacement of the superstructure are not more than 12%, which indicates that the natural frequencies and the seismic response of the structure are not sensitive to double-thin-wall distance.So during the period of primary design, the effect of double-thin-wall distance on the dynamic performance of continuous rigid frame bridge can be neglected if the bridge has ordinary double-thin-wall distance.
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表 1 不同双薄壁墩间距条件下桥梁的自振频率
Table 1. Natural frequencies of bridge under different double-thin-wall distances
Hz 阶次 L/25 L/22 L/20 L/15 L/12 频率 振型描述 频率 振型描述 频率 振型描述 频率 振型描述 频率 振型描述 1 0.337 桥墩纵弯 0.349 桥墩纵弯 0.356 桥墩纵弯 0.365 桥墩对称横弯 0.365 桥墩对称横弯 2 0.366 桥墩对称横弯 0.366 桥墩对称横弯 0.366 桥墩对称横弯 0.377 桥墩纵弯 0.388 桥墩纵弯 3 0.839 桥墩反对称横弯 0.838 桥墩反对称横弯 0.837 桥墩反对称横弯 0.834 桥墩反对称横弯 0.831 桥墩反对称横弯 4 1.179 主梁竖向对称弯曲 1.205 主梁竖向对称弯曲 1.220 主梁竖向对称弯曲 1.256 桥墩对称纵弯+主梁竖弯 1.263 桥墩纵向反对称弯曲 5 1.414 桥墩纵向反对称弯曲 1.427 桥墩纵向反对称弯曲 1.434 桥墩纵向反对称弯曲 1.451 桥墩纵向反对称弯曲 1.447 桥墩纵向反对称弯曲 6 1.502 桥墩纵向弯曲(主梁竖向弯曲) 1.511 桥墩纵向弯曲(主梁竖向弯曲) 1.518 桥墩纵向弯曲(主梁竖向弯曲) 1.558 主梁竖向对称弯曲 1.622 主梁竖向弯曲 7 1.974 主梁横向对称弯曲 1.971 主梁横向对称弯曲 1.969 主梁横向对称弯曲 1.959 主梁横向对称弯曲 1.949 主梁横向对称弯曲 8 2.384 主梁竖向反对称弯曲 2.426 主梁竖向反对称弯曲 2.457 主梁竖向反对称弯曲 2.495 主梁扭转(1个桥墩横向弯曲) 2.466 1个桥墩横向弯曲(主梁扭转) 9 2.543 1个桥墩横向弯曲(主梁扭转) 2.533 1个桥墩横向弯曲(主梁扭转) 2.526 1个桥墩横向弯曲(主梁扭转) 2.581 主梁竖向反对称弯曲 2.648 1个桥墩横向弯曲(主梁扭转) 10 2.732 1个桥墩横向弯曲(主梁扭转) 2.723 1个桥墩横向弯曲(主梁扭转) 2.715 1个桥墩横向弯曲(主梁扭转) 2.683 主梁扭转(1个桥墩横向弯曲) 2.705 主梁竖向反对称弯曲 表 2 模式1下桥梁地震响应
Table 2. Seismic response of bridge under mode 1 excitation
间距 主梁竖向弯矩/ (MN·m) 主梁扭矩/ (kN·m) 墩底纵向弯矩/ (MN·m) 主梁纵向位移/ (cm) 截面1 截面2 截面3 截面4 截面1 截面2 截面3 截面4 截面5 截面6 截面1 截面2 截面4 L/25 8.4 17.3 16.1 2.1 327 706 581 286 9.2 9.2 3.72 3.76 3.71 L/22 7.4 16.3 15.7 2.2 356 729 563 308 9.8 9.8 3.64 3.67 3.62 L/20 7.6 15.5 15.2 2.2 356 697 607 307 10.2 10.2 3.72 3.76 3.71 L/15 6.5 12.9 16.1 2.2 356 580 614 266 11.0 11.0 3.55 3.57 3.52 L/12 5.5 11.0 15.0 2.0 355 503 588 235 10.6 10.6 3.30 3.32 3.28 表 3 模式2下桥梁地震响应
Table 3. Seismic response of bridge under mode 2 excitation
间距 主梁横向弯矩/ (MN·m) 主梁扭矩/ (kN·m) 墩底横向弯矩/ (MN·m) 主梁横向位移/ (cm) 截面1 截面2 截面3 截面4 截面1 截面2 截面3 截面4 截面5 截面6 截面1 截面2 截面4 L/25 10.7 15.9 16.1 30.8 5 344 5 605 1 817 177 26.6 30.5 1.88 3.75 5.23 L/22 10.8 16.0 16.1 30.9 5 357 5 620 1 828 181 26.5 30.7 1.88 3.77 5.25 L/20 10.9 16.1 16.2 31.0 5 366 5 627 1 837 184 26.4 30.9 1.88 3.79 5.25 L/15 11.2 16.3 16.4 31.2 5 402 5 650 1 863 192 26.1 31.5 1.89 3.50 5.29 L/12 11.5 16.6 16.7 31.4 5 434 5 662 1 880 202 25.9 32.1 1.91 3.48 5.31 -
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