封闭式薄膜屋盖的参数共振分析

膜结构的非线性风振响应是流固耦合的共同作用问题,当脉动风频率与结构频率满足一定关系时,就有可能出现大幅参数共振。本文首先假定风为无粘性势流,利用室内外空气速度势函数、屋面涡旋以及尾流涡旋来模拟屋面与风场之间的大气湍流边界层。针对封闭式薄膜结构受纵向脉动风荷载作用下,推导了屋面所受的气动力表达式,建立了薄膜屋盖参数振动的非线性力学模型。然后通过数值计算分析,证明了薄膜屋盖在达到临界颤振风速之前有参数共振的可能性。因而,在实际工程中应该考虑出现参数颤振的可能性,通过调整结构参数或预应力,以降低参数共振的频率范围。

Parametric resonance analysis of closed membrane roofs

Wind-Induced dynamic response of the membrane structures belongs to fluid-structures coupling interaction,when a certain relation between frequency of fluctuation wind and natural frequency of the membrane roof exists,large amplitude parametric resonance can be induced.Firstly,based on the characteristics of fluctuation wind,with the assumption of wind is inviscid potential flow,the paper simulate the atmospheric turbulence boundary layer by velocity potential function of indoor and outside air flow fields,vortex sheet over roof and that in the waked flow.For a closed membrane structure subjected to wind in longitudinal direction in atmospheric turbulence,the paper deduced aerodynamic force over the roof,then mechanical model for parametric vibration problem of membrane roofs is presented and studied with numerical method.The numerical results for an example suggests that there exists the possibility of the appearance of parametric resonance at rather lower wind speed than flutter critical wind velocity. Therefore,in the practical engineering,we should take into consideration the possibility of the resonance,and decreased the range of resonance by changing scale parameters or pretension.