角对角双子塔的气动特性及其抗风设计

Aerodynamic characteristics and wind-resistant design of diagonal twin towers

为了给角对角双子塔的抗风设计提供参考,采用同步测压风洞试验方法,从结构风荷载与风振加速度的角度研究了角对角双子塔在不同间距和不同风向角下的气动特性与风振响应特点。研究结果表明:就风致响应而言,角对角双子塔存在两个最不利风向角,分别为斜向45°左右和近串联方向的80°左右;在45°风向角附近,角对角双子塔会出现振幅较大的横风向涡激振动,但受到双塔间的气动干扰作用,相应的横风向涡激振动将小于独塔情况,且双塔间有利的气动干扰作用对上游塔比对下游塔更加明显;在80°风向角附近时下游塔将受到上游塔的尾流影响,有可能出现较大振幅的尾流抖振响应;45°左右风向角产生的横风向涡激振动主要出现在亚临界至临界风速下,风速相对较低;80°左右风向角出现的尾流抖振主要发生在超临界风速下,风速相对较高。考虑到大多数超高层建筑的设计风速都小于或接近涡激临界风速,因此控制45°风向下的横风向涡激振动是抗风设计的关键。在这种情况下,采用较小间距的角对角双子塔对抗风设计有利。

By adopting wind tunnel model tests with synchronous pressure measurement,the aerodynamic force and wind response characteristics of diagonal twin towers under different spacing and wind directions were investigated from the perspectives of structural wind load and wind-induced acceleration,which is expected to provide reference for the wind-resistant design of diagonal twin towers.Results show that there were two most unfavorable wind directions in terms of wind responses:diagonal direction(around 45°)and near tandem arrangement direction(around 80°).In the wind direction of around 45°,the diagonal twin towers experienced remarkable across-wind oscillations caused by vortex shedding.However,due to the aerodynamic interference between the two towers,these across-wind oscillations were smaller compared with the single tower under the same wind conditions.Moreover,the favorable aerodynamic interference was more evident on the upstream tower than on the downstream tower.In the wind direction of around 80°,the downstream tower was excited by the wake of the upstream tower,which might result in severe wake-buffeting in the across-wind direction.The across-wind oscillation due to vortex shedding in around 45°wind direction mainly occurred at a subcritical to critical wind speed of vortex-shedding,and the wind speed was relatively low.The critical wake-buffeting under a wind direction of about 80°mainly occurred at supercritical wind speeds,and the wind speed was relatively high.Since the design wind speeds for super-tall buildings are mostly lower than or close to the critical wind speed of vortex shedding,the control of the across-wind oscillation for wind direction of about 45°is the key to wind resistance design.In this case,it is beneficial to designing diagonal twin towers with smaller spacing.