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为探讨三塔悬索桥与两塔悬索桥静动力特性差异与中塔选型,以泰州长江大桥为原型,基于有限位移理论建立相应的两塔、三塔(混凝土中塔与钢中塔)悬索桥的空间有限元模型,分析了各种结构参数下的静力和地震效应。研究结果表明:与两塔悬索桥相比,由于中塔顶缺乏边缆的有效纵向约束,三塔悬索桥整体刚度较小,变形较大,自振频率低;汽车作用下主缆抗滑、桥塔受力、主梁挠跨比等在常规两塔悬索桥中很容易满足要求的指标,但对三塔悬索桥却成为控制指标。三塔悬索桥的3个指标都与中塔抗推刚度密切相关,但其对中塔抗推刚度的需求是矛盾的。“人”字形钢中塔三塔悬索桥的主缆抗滑安全系数为2.17,汽车作用下桥塔最大应力为182 MPa,最大挠跨比为1/210,全部满足要求。可见,“人”字形钢中塔较好地兼顾了3个控制指标的需要,做到了构件刚度和缆索体系刚度的优化,是合理的中塔形式。
In order to discuss the difference of static and dynamic characteristics and mid-tower selection between three-tower suspension bridge and two-tower suspension bridge, the corresponding two-tower and three-tower suspension bridge The finite element model is used to analyze the static and seismic effects under various structural parameters. The results show that compared with the two-tower suspension bridge, due to the lack of effective longitudinal restraint of the side cable in the mid-tower, the overall stiffness of the three-tower suspension bridge is small, the deformation is large and the natural frequency is low. Forced, the main beam flexspan ratio in the conventional two-tower suspension bridge is very easy to meet the requirements of the indicators, but the three towers of the suspension bridge has become a control index. The three indexes of the three-tower suspension bridge are closely related to the anti-push stiffness of the middle tower, but their demand for the anti-push stiffness of the middle tower is contradictory. The anti-skid safety factor of the main cable of the tower-shaped three-tower suspension bridge of “Ren” shape steel is 2.17, the maximum stress of the tower is 182 MPa under the action of automobile, and the maximum flex-span ratio is 1/210, all meeting the requirements. Can be seen, “person ” shaped steel tower to better take into account the needs of three control indicators, to achieve the stiffness of the components and the stiffness of the cable system optimization, is a reasonable tower form.