大跨度桥梁中央开槽颤振控制效果和机理研究

采用理论分析结合风洞试验的方法,对中央开槽这种已经在大跨度桥梁设计和建设中逐步得到应用的颤振控制措施的控制效果和控制机理进行研究。选取5种不同气动外形的基本断面,采取2种开槽宽度分别对其进行中央开槽处理。对全部5个系列15种断面开展节段模型风洞试验,并应用二维三自由度耦合颤振分析方法,对各断面开槽前后颤振性能、颤振驱动机理和颤振形态的变化规律进行分析。研究结果表明,中央开槽并不总是能提高结构的颤振稳定性能,其控制效果同基本断面的气动外形以及开槽宽度密切相关,当槽宽不恰当时中央开槽的控制效果会严重削弱,而对气动外形比较钝化的断面采用中央开槽后其颤振性能反而会恶化。对控制机理的理论分析表明,这种控制效果差异的原因在于各断面气动阻尼的形成和随风速发展规律存在明显差别,而颤振形态特别是竖向自由度的参与程度也影响到中央开槽的颤振控制效果。

Flutter control effect and mechanism of central-slotting for long-span bridges

Flutter control by use of central-slotting has gradually been adopted in the design and construction of long-span bridges as an effective control measure.This subject was investigated through both theoretical analysis and wind tunnel test.Five basic girder cross sections representing five typical aerodynamic configurations were selected and central-slotted with two different slot widths.A series of sectional model tests and theoretical analyses based on the two-dimensional 3-DOF coupling flutter analysis method(2d-3DOF method) were carried out to investigate the aerodynamic performance,flutter mechanism and flutter modality of the five basic sections and the corresponding central-slotted sections.The results indicate that central-slotting can not always improve the aerodynamic stability of a bridge structure.The control effect of central-slotting depends heavily on the aerodynamic configuration of the original girder section and the corresponding central-slotting width.If the original section is inappropriate or the slot width is unsuitable,central-slotting would even deteriorate the structural flutter performance.Theoretical investigations indicate that the differences in flutter control effects result from the different formations and evolution trends of aerodynamic damping,and that flutter modality,especially the participation level of heaving motion,also has a significant influence on the control effect of central-slotting.