双缆悬索桥空缆状态主缆抗滑安全性研究

为指导双缆悬索桥上下缆垂跨比的取值,明确双缆悬索桥施工阶段主缆抗滑稳定性,提出一种主缆在施工阶段空缆状态下的抗滑安全系数计算方法。基于上缆变下缆的主缆布置方式,通过双缆悬索桥成桥状态反推空缆状态主缆垂度,根据空缆状态下主缆线形为悬链线计算中塔塔顶鞍座处缆力及包角,并据此计算空缆状态抗滑安全系数。建立多塔悬索桥有限元模型对提出的公式进行验证,分析成桥状态上下缆垂跨比和桥梁跨度的取值对空缆到成桥状态主缆垂度变化以及抗滑安全系数的影响。结果表明,采用本文公式计算的双缆悬索桥空缆状态下抗滑安全系数精度较高;上下缆垂跨比对空缆状态主缆抗滑安全性影响较大,抗滑安全系数随着上下缆垂跨比差值的增大迅速减小;空缆状态主缆抗滑安全系数受跨度影响不大,其随跨度增大略有提高。在实际的双缆悬索桥初步设计过程中应考虑施工阶段主缆抗滑稳定性,选择适宜的上下缆垂跨比,采取措施提高施工阶段主缆抗滑安全性。

Study on anti-sliding safety of main cable in the cable-finished state of double-cable suspension bridge

In order to guide the selection of the right value of the sag-span ratio of the top and bottom cables and understand the anti-sliding stability of the main cable during the construction stage of double-cable suspension bridge, a theoretical calculation method of the sliding-resistance coefficient in the cable-finished state at construction stage is proposed.Based on the "the top cable to bottom cable" layout, the sag of the main cable in the cable-finished state is deduced through the bridge-finished state, according to the catenary shape of the main cable in the cable-finished state, the cable force and cornerite of the main cable on the tower top are calculated, and the sliding-resistance coefficient in the cable-finished state is calculated.The FE model of a multi-tower suspension bridge is established to verify the proposed formula, and the influence of different sag-span ratios of top and bottom cables and span on the variation of main cable sag from the cable-finished state to the bridge-finished state and the sliding-resistance coefficient are analyzed.The results show that the proposed formula has a satisfactory accuracy in calculating the sliding-resistance coefficient of the double-cable suspension bridge in the cable-finished state;The sag-span ratio of the top and bottom cables has a great impact on the anti-sliding safety of the main cable in the cable-finished state, the sliding-resistance coefficient decreases rapidly with the increase of the difference between the sag-span ratio of the top and bottom cables;The span has a small influence on the sliding-resistance coefficient of the main cable in the cable-finished state, and it increases marginally with span length.In the actual design process of the double-cable suspension bridge, the anti-sliding stability of the main cable at construction stage should be considered, the appropriate sag-span ratio of the top and bottom cables should be selected in combination with the measures to improve the anti-sliding stability.