考虑索局部振动的斜拉桥动力特性研究——杭州湾跨海大桥北航道桥动力特性分析

Dynamic characteristic research of cable-stayed bridges considering cable local vibration: Dynamic behavior analysis of northern channel bridge in Hangzhou Bay

以主跨为448m的杭州湾跨海大桥北航道桥为例,研究了考虑拉索局部振动的斜拉桥动力特性.利用子结构方法,把索的振型作为广义自由度来考虑拉索局部振动.该方法与把拉索划分为多个单元的链杆法相比,具有自由度少并且计算精度不受影响的优点.研究结果表明,当考虑拉索局部振动时,会出现拉索与主梁或桥塔的耦合振型,这种索桥耦合振动现象在以往把拉索作为单一单元的斜拉桥动力特性分析中不会出现.索的局部振动虽然对结构主要振型的频率影响不大,但对振型能量分布有比较明显的影响.对发生索桥共振的振型,如不考虑索的局部振动,通常会使索的阻尼估计过高,而索的振动能量估计偏低,不能很好地反映大跨度斜拉桥的动力特性.

The dynamic characteristic analysis was carried out on the northern channel bridge in Hangzhou Bay of 448 m span scheme with cable local vibration taken into consideration. The cable local vibration was included by treating cable modes as generalized freedom and using the concept of substructure. The results show that many cable-deck and cable-tower couple modes appear when cable local vibration is considered, which can not be predicted by one-element cable method. Compared with multi-link method that divides the cable into several elements, this method has less freedom and almost the same precision. The dynamic characteristics of the bridge structure cannot be described correctly if cable local vibration is not involved. Cable local vibration has little effect on the modal frequency, but more on the modal energy distribution. The cable damping will be overestimated while cable energy underestimated in those modes prone to cable local vibration if it is not considered.