为有效揭示预应力薄膜充气梁的模态特性,文中首先根据柔性薄膜结构的受力特点,考虑大变形、初始预应力等几何非线性效应,通过小杨氏模量法找形分析得到平衡形态,继承其位形与初始平衡应力;然后采用分块兰索斯法对薄膜充气梁模态进行数值计算分析,考察了影响薄膜充气梁模态特性的主要因素：压力、薄膜厚度、管径;最后,提出薄膜结构湿模态概念,考虑外流场对薄膜充气梁的耦合作用,分别采用拟密度法和流固耦合法计算了薄膜充气梁的湿模态,通过与干模态的比较验证了外流场对薄膜充气梁的耦合效应.

In order to reveal the modal behaviors of inflatable fabric beams （ IFB） ,first,the equilibrium shape of IFB is obtained via the form-finding of small Yung＇s Modulus method,with the loading characteristics of flexible membrane structures and the nonlinear geometric factors such as the large deformation and the initial prestress being considered. Thus,the configuration and initial equilibrium stress are sequentially inherited. Next,the modes of IFB are numerically calculated and analyzed by means of the block-Lanczos method,and the effects of pressure, fabric thickness and radius （ slenderness） on the modal behaviors of IFB are analyzed. Then,the wet mode of IFB is proposed and is computed respectivelg via the approximate density method and the fluid-structure interaction method with the consideration of the coupling between the external air fluid field and the flexible IFB. Finally,a comparison between the wet mode and the dry mode of IFB is made. The results validate the coupling effect between the external air fluid and the IFB.