中文摘要：

研究了双主缆悬索桥体系在承受不平衡活载时的力学特性——双缆体系根据荷载在上缆与下缆间的分配情况，可等效为一根虚拟主缆；单跨加载时，加载跨主缆内力增大，非加载跨荷载由下缆向上缆转移，虚拟缆垂度减小，以达到与加载跨主缆的内力平衡．根据加载跨与非加载跨主缆水平力相等的关系，通过求解虚拟缆的垂度，得到了荷载在上缆与下缆间的分配比例，建立了有限元模型进行验证，并与理论值进行了对比．结果表明，双缆体系在承担不平衡活载时，其塔顶位移及跨中挠度远小于传统悬索桥．

英文摘要：

This paper deals with the mechanical properties of a suspension bridge with double main cables under unbalance load. The double-main cable system can be equivalent to a virtual main cable according to the distribu- tion of the load between the top cable and the bottom cable. Under single-span load, the cable force on the load span increases, the load on the adjacent span transfers from the bottom cable to the top cable, and the sag of the virtual cable decreases, so that the cable force balances with the load span. According to the equivalent relation of the cable force between the load span and the adjacent span, the distribution ratio of the cable force loading on the top cable and the bottom cable is obtained by calculating the sag of the virtual cable. Moreover, a finite element model is established to verify the proposed theory, and the results are compared with the theoretical ones. It is found that both the deformation of the pylon and the mid-span deflection of the double-main cable system under un- balanced live loads are much less than those of the traditional suspension bridge.