摘要
该文详细介绍了有理函数与阶跃函数在桥梁气动自激力时域模拟中的应用。分别对两种表达式的极限特性与瞬态特性进行了分析。理论分析与数值结果表明:阶跃函数的极限特性独立于识别参数而与桥梁断面的准定常风荷载特性相一致,经参数识别后的阶跃函数自激力表达式是准定常风荷载模型与基于颤振导数表达的自激力模型两者的统一。因此,阶跃函数自激力模型可应用到响应均值非零的结构风振响应分析中。相比之下,有理函数模型的极限特性依赖于所识别的参数,与准定常风荷载特性并不存在统一的关系,因而通常情况下其应用范围限定在均值为零的桥梁风振响应分析中,该文通过分析讨论指出,可通过强制有理函数表达式中若干参数值的方法克服这一缺陷。无论是阶跃函数还是有理函数模型,由于其参数识别是按照自激力平稳谱特性等效的原则完成,因而其识别参数所决定的瞬态特性仅仅是一种数值结果,并不代表实际桥梁断面的瞬态气动力特性。由此可能会产生高瞬态值与十分耗时的衰减过程,这种不良瞬态特性会引起结构风振时域分析中长时间范围的自激力模拟失真。该文通过限定时域自激力表达式中记忆项参数的识别数值范围,有效地解决了这一问题。
This paper introduces the application of a rational and indicial function in the time-domain simulation of bridge deck self-excited aerodynamic forces.The limiting and transient characteristics of both expressions are analyzed and compared.Theoretical analysis and numerical results indicate that the limiting characteristics of the indicial function,independent on the identified parameters,are in consistent with the quasi-steady wind-load characteristics.Thus,the indicial-function-expressed self-excited force model is a unification of two models： the self-excited aerodynamic forces expressed with flutter derivatives and the quasi-steady wind loads described with aerostatic load coefficients.It is this kind of unification that makes the indicial functions capable of the analyzing of wind-structure interaction with nonzero mean response values,such as the case where the effects of mean wind loads are included.In contrast with the indicial functions,limiting characteristics of the rational functions are completely dependent upon the parameters identified and not in consistent with the quasi-steady wind-load characteristics.As a result,its application should be limited within cases with zero mean values of vibration.A method is presented in this paper to meet such shortcomings of the rational functions which compels equivalence between some parameters and the quasi-steady wind-load characteristics.The transient characteristics of both the indicial function and rational function,which depend upon the identified parameters,are mere numerical results and may not represent the real transient aerodynamic characteristics of bridge decks.This is due to only the spectrum equivalence of self-excited forces,which does not include transient characteristics,is involved in the identification of function parameters.Consequently,very high transient values and time-consuming attenuating process may be formed,which result in long-playing distorted simulation of self-excited aerodynamic forces during the time-domain analysis of a wind-structure interaction.An effective measure,which may overcome this phenomenon by predefining numerical range for exponential parameters,is available in this literature.
出处
《工程力学》
EI
CSCD
北大核心
2011年第2期75-85,共11页
Engineering Mechanics
基金
国家自然科学基金项目(50708036)
国家自然科学基金重点项目(50738002)
关键词
桥梁
自激力
时域
有理函数
阶跃函数
瞬态特性
极限特性
bridge
self-excited force
time-domain
rational function
indicial function
transient characteristic
limiting characteristic
