Research On Structural System And Mechanical Characteristic Of Long-Span Double-Cable Suspension Bridge

As a new form of suspension bridge structure, double-cable suspension bridge has significant differences with the traditional single-cable suspension bridge in structure systems, mechanical properties and computational analysis methods. To study the influences of structure system selection and design parameters on mechanical properties systematically and deeply has theoretical and practical significances. Key issues related to structure systems and mechanical properties of double-cable suspension bridge are studied by finite element method to draw some valuable conclusions, which can offer a scientific basis for the conceptual design and preliminary design of long-span double-cable suspension bridge. The main research contents are as follows:(1) With a typical long-span highway suspension bridge as the engineering background,3-D finite element models of the twin-tower and three-tower suspension bridges with single-cable and double-cable structures are established respectively, and the static characteristics and natural vibration characteristics of finished bridges under the effect of live load and static wind load are analyzed. The results show that the double-cable suspension bridge in comparion with single-cable suspension bridge can improve the vertical stiffness of bridge structure but reduce the lateral stiffness to some extent.(2) Based on the three-tower and four-span suspension bridge with double main cables, the influences of the main structural design parameters on the mechanical properties are analyzed and the actual effects of the main parameters, including the side to center span ratio, the stiffness of middle bridge tower, the distribution ratio of dead load to bottom cable and top cable and the rise-span ratio, on the structure internal force and deformation of main cables, girders and towers, and on the natural vibration frequency are also determined. Finally some valuable conclusions are provided.(3) Combined with the structural characteristics of double-cable suspension bridge, the safety problems of slippage resistance between main cable and saddle at middle tower are studied. Two saddle forms suitable for the double-cable suspension bridge are put forward, and the influences of the main parameters, including the stiffness of middle bridge tower, the distribution ratio of dead load to bottom cable and top cable and the rise-span ratio, on the safety factor of main cable against sliding at the top of middle tower are also analyzed.