多塔部分斜拉桥自振频率的实用简化算法

The practical simplification algorithm of multi-pylon extradosed cable-stayed Bridge fundamental frequency

为了便于在概念设计阶段快速准确地估算多塔部分斜拉桥的基频,根据Rayleighmethod方法,以主梁的静挠度曲线作为振型函数,推导支承体系和刚构体系多塔部分斜拉桥的基频估算公式。以某三塔部分斜拉桥为例,计算其频率,讨论结构体系及塔跨数对多塔部分斜拉桥基频的影响。并将公式与较为精确的有限元法和《公路桥涵抗风设计规范》的单一估算方法进行比较,研究结果表明:计算多塔部分斜拉桥基频不可忽略结构体系及塔跨数的影响;支撑体系基频远低于刚构体系,不可用单一公式计算;随着塔跨数增加,基频降低。有限元解与公式解的对比结果表明,公式基频误差在10%以内,可以满足工程概念设计的需要。

In order to estimate the fundamental frequency of multi tower cable-stayed bridge quickly and accurately in the conceptual design stage,this paper according to the Rayleigh method,took the static deflection curve of the main beam as the shape function,deduced the fundamental frequency estimation formula of the supporting system and rigid frame system of multi tower partial cable-stayed bridge.Taking a three towers partial cable-stayed bridge as an example,discuss the effect of structural system and tower number on the fundamental frequency of cable stayed bridge.Finally,the formula was compared with a more accurate finite element method and the single estimation method in“highway bridge wind resistant design specification”.The results show that the influence of structural system and tower number can’t be ignored in calculating the frequency of multi tower partial cable-stayed bridge:the frequency of support system is far lower than the rigid system,indicating a single formula is not accurate;with the increase in the number of towers,the frequency is reduced.The comparison results of the finite element solution and the formula shows that the error of the formula is less than 10%,which can satisfy the need of engineering concept design.