Research On Form Finding And Wind-Induced Vibration Of Tensioned Membrane Sructures

Since the second half of the last century, tensioned membrane structures have attracted great attention because of their novel shape and reasonable behavior. Different from the traditional structures,tensioned membrane structure is supported by flexible cables or rigid supports to cover a large space.Although some progress in our country have been made,compared with some advanced countries,the research level in China is left behind.Form finding and analysis of response to wind are still hot and difficult subjects,which is studied in this thesis. Finite element method is an effective tool for solving complex problems.The besic formulation of geometricial non-linear finite element method, tri-node triangle element which model membrane, and two-node link element which model cable are introduced firstly. Because the stiffness of tensioned membrane structures are dependent on geometrical curved surface and prestress, finding the initial equilibrium shape and surface stress distributing become a crucial process.Based on discusson of principles and means of seaking for initial shape, a finding form program(FFFD) is written in FORTRAN according to force density theory. Another finding shape means,pedestal-shifting method is introduced, meanwhile, small Young's modulus which is used in pedestal-shifting method is addressed in detail, and general steps of pedestal-shifting method in ANSYS are listed. In addition, based on the comparison of above two methods, mixed method is put forward, which can improve the efficiency of finding shape. Obviously,tensioned membrane structures are sensitive to wind.Generally,people analyse the response to wind load in time domain ,and digital simulation of wind field velocity is the foundation of calculating the response. The spectral representation method is adopted to simulate the stochastic wind field in this thesis,and an application program(WIND-VEL) is also carried out use MATLAB. Due to the geometrical non-linear behavior of tensioned membrane structures,the couple interaction between wind and structure must been considered. MATRIX27 element in ANSYS rather than the damping caused by wind is adopted to analyse the structure response to wind,which not only avoid the heavy task of programming, but also offer a new way to adopt general finite-element softwares to study the wind sensitive structures such as membrane.