Study On Wind-Structure Interaction In Wind-Induced Vibration Of Membrane Structure

Membrane structures are widely used as long-span structures. As being characterized by lightweight and flexibility, they are highly susceptible to the wind action, in particular, to the effects of fluctuating pressure. Membrane structures often produce rather big vibration under wind excitation, which may even affect the wind pressure distribution. That is to say, the interacting occurs between wind and structures, which is called"fluid-structure interaction"in the fluid dynamics. It is necessary to pay attention to"fluid-structure interaction"besides using the traditional analysis methods in order to accurately estimate the wind load and wind-induced vibration response on membrane structures. Because of complexity of mechanical property, especially geometrical non-linearity, the wind-structure interaction of membrane structure is very sophisticated. So at the present, the study of"fluid-structure interaction"is in the starting step.Firstly, based on loose coupling partitioned method, a wind-structure interaction numerical simulating platform of membrane structure has been established in the environment of Compaq Visual Fortran 6.5 (the method is called"the direct numerical simulation"). The program is modularized, in which geometry modeling modul, fluid module, structure module and data interface modul keep independent each other. In geometry modeling modul, the form-finding analysis program of membrane structure is adopted. In fluid analysis modul, the CFD software FLUENT6.0 is adopted. In structure analysis modul, the dynamic analysis program MDLFX is adopted. In data interface modul,"Thin-Plate Splines"is adopted to resolve the data transfer on coupling boundary between CFD and CSD. And the problem on dynamic mesh is effectively resolved by using algebra method and iteration method. Finally, the numerical simulation of the wind-structure interaction of one-way long-span roofs and three-dimensioned saddle-shaped membrane structure are carried out to validate the method.Because of the hundredfold time-consuming of simulating the three-dimensioned problem and lack of engineering operability by using the direct numerical simulation, a simplified numerical approach of a time-dependent wind-structure interaction is presented. The general idea of this approach is to divide the structural response into three components: mean response, background response and resonant response. The first component is a static interaction process, which is due to the change of structural geometry under mean wind pressure. The second component can be regard as a qusi-static interaction process, which relates to the motion of large scale eddies. The last component can be called as a transient interaction process, in which the dynamic magnification effect should be considered mainly. Due to the different characteristics of each component, different methods should be adopted respectively. For static and quasi-static interaction, the suitable method is CFD simulation, in which the wind pressure change due to structural deformation will be considered mainly; for transient interaction, the suitable method is nonlinear random vibration analysis in time domain considering the influence of added mass and aerodynamic damping.Effect factor of Fluid-Structure Interaction (FSI) is defined to consider the influence of fluid-structure interation. Then, systemically studies on the behaviors of one-way long-span roofs and three-dimensioned membrane structures are carried out. The effects of several factors, such as wind velocity, wind direction, height-span ratio and pretension force et al, are investigated, and the effect factor of FSI is advised.Furthermore, based on energy conservation law, the analytic formula of added mass and aerodynamic damping is present. Then the aerodynamic force in the formula is derived by using aeroelasticity theory. Finally, the effects of several factors to the added mass and aerodynamic damping of membrane structures, such as wind velocity, wind direction, height-span ratio and pretension force et al, are investigated.