Research On Critical Wind Speed Of Aeroelastic Instability Of The Pretensioned Membrane Structure

Membrane structures are so vulnerable to large scale deformation and vibration in wind field as fluid-structure interactions are not neglectable.This kind of interaction would cause a steady increment on the deformation and the amplitude of vibration in some circumstances,which is called aeroelastic instability.The solution of the critical velocity of the aeroelastic instability has always been a tough issue.In this dissertation,an improved analytical method is proposed to seek for the critical wind speed.Adopting the hypothesis that the fluid field is potential,the author establishes the analytical model of the vibration of one-way tensioned membrane based on the vibration equation of membranes,and the analytical model of the vibration of H.P.shaped tensioned membrane based on the non-moment theory of flat shells and the vibration equation of membranes.An analytical solution to the aerodynamic pressure on the surface of the membrane is proposed based on the potential flow theory,the subsonic lifting surface theory and the symmetrical airfoil theory.The Galerkin method is used to find out the ordinary differential equation of vibration about the generalized coordinate of a given vibration mode,from which the criteria and the critical wind speed of the aeroelastic instability are obtained.By using the method of this dissertation,the critical wind speed of the rectangular plane one-way tensioned membrane,the rectangular plane H.P.shaped tensioned membrane and the rhombus plane H.P.shaped tensioned membrane is analyzed.The effects of pretension,plane aspect ratio and rise-span ratio on the critical wind speed are discussed and some suggestions of avoiding the instability are made.The contents of the dissertation are as follows:1.An introduction and comparison of investigations made by scholars home and abroad.2.An improved analytical method for aeroelastic instability of membrane structures is proposed.Unlike the previous analytical method,the subsonic lifting surface theory is used to solve the aerodynamic pressure of wind when going through the draped direction of the H.P.Shaped tensioned membrane.The difference between the half space unbounded Poisson equation and the full space unbounded Poisson equation is used to distinguish the aerodynamic force between the closed membrane structure and the open membrane structure.The relaxation effect of the membrane induced drag on the membrane pretension is also considered.3.By using the method of this dissertation,the critical wind speed of the rectangular plane one-way tensioned membrane,the rectangular plane H.P.shaped tensioned membrane and the rhombus plane H.P.shaped tensioned membrane is analyzed.The characteristics of the aeroelastic instability of the structure are summarized,and the criteria for solving the critical wind speed are established.The effects of pretension,plane aspect ratio and rise-span ratio on the critical wind speed are analyzed,and some measures to prevent instability are given.Compared with the test results of Chen Zhaoqing,Uematsu Y and Uchiyama K,the theoretical solutions bear a high coincidence to the test results,and the accuracy is greatly improved compared with the previous analytical method.4.The results indicate that the critical wind speed of aeroelastic instability of membrane structures increases with the increase of modes and prestress.In some cases,increasing the rise-span ratio of structures can significantly increase the critical wind speed of instability.Open membrane structures are more vulnerable to instability than closed membrane structures.When choosing the rectangular planar shape,attention should be paid to the choice of the plane aspect ratio.Generally,the smaller plane aspect ratio should be chosen as far as possible.