大跨度人行悬索桥抗风缆经济化设计的研究

Study of economic design of wind-resistant cables for large-span pedestrian suspension bridges

空间抗风缆是提高大跨度人行悬索桥刚度的常用结构,其用钢量较高(普遍超过主缆用钢量的30%,甚至超过60%),对工程造价影响较大。为设计经济合理的抗风缆结构,依据国内现行规范分析结构强度、刚度、抗风稳定性等静动力特性控制指标要求,从结构总体布置参数拟定、静力分析选型、抗风稳定性验证等方面普适性地阐述满足静动力指标要求的抗风缆设计流程,并深入研究抗风缆总体布置中理论倾角及矢跨比选取、结构选型中初始截面尺寸及初张拉力拟定、抗风稳定性中动力特性参数影响等方面的关键技术要点。为详细展示实际工程中经济合理的抗风缆设计过程,以某峡谷景区300 m主跨人行悬索桥为工程实例,按普适性设计流程初拟多种抗风缆结构方案,经全桥有限元理论分析及节段模型风洞试验比选验证后选出经济性相对较好的抗风缆布置方案;抗风缆系统理论斜面水平夹角为30°,理论矢跨比为:1/12,单侧抗风主缆采用7根直径D52 mm钢丝绳(6×55SWS+IWR),用钢量约为主缆的58%,抗风缆强度及全桥整体结构刚度满足静力设计指标要求,全桥结构的静风稳定性及颤振稳定性满足规范要求。研究成果可为后期类似项目设计提供参考。

The spatial wind-resistant cable is a common measure to improve the stiffness of large-span pedestrian suspension bridges. The amount of steel used in wind-resistant cables is generally high and can exceed 30% or even 60% of the steel used in the main cable, which significantly impacts the engineering cost. In order to design an economical and reasonable wind-resistant cable of pedestrian suspension bridges, this paper first analyzed the control index of static and dynamic properties in conjunction with the current domestic design codes, such as strength, stiffness, and wind resistance stability. Then, the design process was universally amplified in terms of general arrangement, static computation, and wind resistance stability analysis. This paper investigated the key technical points about the dig angle and rise-span ratio, initial cross section and tensioning force of wind-resistant cable, and the influence of dynamic property. A pedestrian suspension bridge with a main span of 300 m at a scenic canyon area was chosen as the project’s background to demonstrate the process of wind-resistant cable design. According to the generic design process of multiple structure options, the horizontal angle of the windresistant cable was 30° with a span ratio of 1/12 by considering the results from finite element analysis of bridge structures and corresponding sectional model wind tunnel tests. The wind-resistant cable adopted wire rope with a diameter of 52 mm(6×55SWS+IWR), and the amount of steel used was approximately 58% of the main cable.The static design indices of the strength of the wind-resistant cable and the structural stiffness of the bridge structure, as well as the static wind stability and flutter stability, satisfy the specification requirements. The study can provide a reference for the design of similar projects in the future.