扁平钢箱梁颤振气动措施试验研究

Experimental Study on Aerodynamic Measures for Flutter of Flat Steel Box Girder

为了研究不同颤振气动措施对扁平钢箱梁的颤振稳定性的影响,通过一大跨悬索桥扁平钢箱梁节段模型风洞试验,分别研究了设置上中央稳定板、封隔不同位置护栏、改变检修道护栏透风率3种措施对主梁颤振临界风速的影响,并利用静三分力与颤振导数的关系对颤振控制特性进行了研究。结果表明:单独设置合适高度的上中央稳定板可以有效提高断面的颤振临界风速;单独对检修道护栏进行一定的封隔(非全封),即适当降低一定的透风率对于提高颤振临界风速是有利的,但受风攻角影响;单独封隔检修道时,0°攻角下主梁断面颤振临界风速随透风率的增加近乎线性降低,而+3°攻角下颤振临界风速随着透风率的增加呈现"先增加后降低"的变化趋势;不受上中央稳定板高度影响,检修道护栏透风率对颤振临界风速的影响存在一个"过渡区间",即50%~75%透风率区间内,颤振临界风速随透风率的变化很小,而此区间外的更高或更低的透风率的改变都会对颤振临界风速产生显著地影响;在设置上中央稳定板的基础上,全封不同位置的护栏对于颤振临界风速的影响各不相同,在全封最外侧检修道护栏时颤振临界风速提高了约13.3%,而在全封外侧防撞护栏时却降低了约18%。在各风攻角下,上中央稳定板间隔设置时的主梁颤振临界风速要普遍低于通长设置时。

In order to study the influence of different aerodynamic measures on the flutter performances of flat steel box girder,through the wind tunnel test on the flat steel box girder segment model of a large-span suspension bridge,the influences of the measures of setting upper central stabilizer,isolating guardrails at different positions,and changing the ventilation rate of the guardrail of maintenance roadway on the critical flutter wind speed of the main girder are studied respectively,and the characteristics of flutter control is explored by using the relationship between static three-component force coefficient and flutter derivative.The result shows that(1)the sectional critical flutter wind speed can be effectively improved by setting upper central stabilizer with appropriate height;(2)it is beneficial to increase the critical flutter wind speed by isolating the guardrail of the maintenance roadway to a certain extent(partially enclosed),i.e.,properly reducing a certain ventilation rate,but it is affected by the wind attack angle;(3)when the maintenance road is isolated separately,the critical flutter wind speed decreases linearly with the increase of ventilation rate at 0°attack angle,while the critical flutter wind speed presents a"first increase and then decrease"trend with the increase of ventilation rate at+3°attack angle;(4)unaffected by the height of upper central stabilizer,there is a"transition interval"(within the interval of 50%-75%ventilation rate)in the influence of the ventilation rate of the maintenance roadway guardrail on the critical flutter wind speed,the critical flutter wind speed varies little with the ventilation rate,while the change of higher or lower ventilation rate outside this interval will have a significant influence on the critical flutter wind speed;(5)when the upper central stabilizer is installed,fully enclosing guardrails at different positions have different influences on the critical flutter wind speed,the critical flutter wind speed increased by about 13.3%when the outermost guardrail of the maintenance roadway is enclosed,while it is reduced by about 18%when the outermost anti-collision guardrail is completely enclosed;(6)at each angle of attack,the critical flutter wind speed of the main girder with the interval setting of upper central stabilizer is generally lower than that with the whole-length setting.