中文摘要：

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。

英文摘要：

In order to discuss the static and dynamic properties differences between three-tower and two-tower suspension bridges,and select the rational structure type of mid-tower,based on the Taizhou Yangtze River Bridge,the 3D space finite element models of two-tower suspension bridge and three-tower suspension bridges with concrete mid-tower and steel mid-tower were set up by finite displacement theory and the static and seismal effects were analyzed under various structural parameters.Analysis result shows that compared with two-tower suspension bridge,because the mid-tower is lack of effective restraints from side cables,three-tower suspension bridge has lower total stiffness,lower natural frequency and larger deflection-to-span ratio of main girder.Under vehicle loads,the anti-slipping safety factor between main cable and saddle,the forces of mid-tower and the deflection-to-span ratio of main girder are not important for two-tower suspension bridge,but become controlling indices for three-tower suspension bridge.The indices are related to the anti-pushing rigidity of mid-tower,but have incompatible demands for the rigidity.Under vehicle loads,when the steel mid-tower with upside-down Y shape is selected,the anti-slipping safety factor between main cable and saddle of mid-tower is 2.17,the maximum stress of mid-tower is 182 MPa,the deflection-to-span ratio of main girder is 1/210,and they meet correlative demands.Obviously,due to the application of steel mid-tower,the indices are rationally considered,the stiffness optimization of components and cable system is achieved,so,it is an appropriate structure for mid-tower.9 tabs,7 figs,13 refs.