大跨桥梁气动耦合抖振响应分析的实用方法

基于单模态响应的SRSS方法因其计算简便 ,是当前工程界分析大跨桥梁抖振的常用方法。但随着跨度增大 ,气动耦合效应对桥梁抖振响应的影响越来越强 ,SRSS方法计算所得的抖振响应将出现较大的误差。而目前国内外提出的考虑气动耦合效应的多模态抖振响应分析方法虽然精度比SRSS方法高得多 ,但计算过程过于复杂 ,难以被工程界接受。本文基于经典的Scanlan抖振分析方法 ,在合理简化的基础上 ,导出了多模态气动耦合抖振响应的近似闭合解 ;定义了描述模态之间耦合程度的模态耦合系数和提出了大跨桥梁气动耦合抖振响应分析的实用方法———修正的SRSS方法。最后以日本明石海峡大桥为例 ,说明了本方法的精度和实用性。

A PRACTICAL METHOD FOR AERODYNAMIC COUPLED BUFFETING RESPONSE ANALYSIS OF LONG-SPAN BRIDGES

The SRSS method,which is based on single mode response,has been widely used at present for analysis of buffeting responses of long span bridges in practical use for its simple and convenient computational procedure.For the sake of increase of bridge spans,effects of aerodynamic coupling on the buffeting responses become greater;the errors in the computed buffeting responses may not be negligible accordingly.The methods considering aerodynamic coupling effects between modes are more precise for computation of buffeting responses than the SRSS method,but their computational procedures are too complex for practical purpose.In this paper,an approximate closed from solution for multi mode aerodynamic coupled buffeting responses is derived based on the classical Scanlan method and some reasonable assumptions.Mode Coupling Coefficient (MCC)to describe the aerodynamic coupling degree between modes is defined and a modified SRSS method for aerodynamic coupling buffeting responses is further developed.Finally the Akashi Kaikyo Bridge is taken as an example to show the precision and practicability of the method.