箱形主梁悬臂水平分离板的颤振控制效果与机理

Control Effect and Mechanism of Cantilever Horizontal Splitting Plates on Flutter Performance of a Box Deck

摘要:

为改善主跨1 400 m钢箱梁斜拉桥颤振稳定性,通过节段模型风洞试验研究了中央稳定板、中央开槽、加装悬臂水平分离板(CHSP)等多种气动控制措施的效果.结果表明,在所研究的各种气动控制措施中,CHSP的效果最好,它可显著改善桥梁的颤振性能,尤其是在+3°风攻角情况下的颤振性能.采用二维三自由度耦合颤振分析方法,对原钢箱梁断面和加装CHSP后的钢箱梁断面进行了颤振驱动机理和颤振形态的分析与对比,结果显示,对于那些气动外形介于流线形和钝体之间的主梁断面,CHSP的颤振控制效果与其宽度及风攻角有很大关系,合理分离板宽度应综合考虑不同风攻角下的颤振控制效果而定.控制机理分析表明:CHSP主要通过改变扭转牵连运动产生的两项气动阻尼随风速的变化规律,以及改变自由度耦合效应这样两条途径来达成了改善颤振性能目的.

关键词:超大跨度桥梁; 颤振控制; 悬臂水平分离板; 控制机理; 颤振形态

Abstract:

Various aerodynamic control measures,such as central stabilizing plate,central slotting and cantilever horizontal splitting plate (CHSP),are investigated via a serious wind tunnel tests of sectional model in order to improve the flutter stability of a steel box deck cablestayed bridge with a main span of 1 400 m.The results show that CHSP is the most effective among the measures investigated,and can significantly improve the bridge flutter performance,especially in the case of +3° wind attack angle.Using a 2dimensional and three degree of freedom (3DOF) coupled flutter analysis method,the flutterdriving mechanism and flutter pattern of both the original box deck and that with CHSP measures are then analyzed and compared with each other.It is found that for the decks with aerodynamic shapes between streamline body and bluff body,the control effect of CHSP on flutter depends on both the width and the wind attack angle.A reasonable width of CHSP should be determined with an integrated consideration of its flutter control effect at various wind attack angles.Moreover,the analysis result of flutter control mechanism of CHSP indicates that the measures of CHSP improves the flutter performance of box deck by changing the variation patterns of two aerodynamic damping items generated by the twistinvolved deck motions,in conjunction with changing the coupling effect among degrees of freedoms.

Key words:superlong span bridge; flutter control; cantilever horizontal splitting plate; control mechanism; flutter pattern