Research On Mechanical Performance Of Membrane Structure With Considering Creep And Environment

Membrane structures are becoming more and more widely used for its excellent architectural expression, and people have paid more and more attention on security and durability of membrane structures which are affected by membrane material’s physical and mechanical properties. Recently research of membrane materials mainly focus on strength index, while it is a pity that have little study on working performance of actual structures. According to the current design standard, we usually adopt the safety factor method in order to meet the engineering design, the key problem of this method is how to define the value of safety factor which is influenced by various elements. Furthermore, because of high research budget, long research cycle and limitation in practical project the research on actual membrane structures have not enough sufficient.Based on the above research background, the dissertation is regarding PTFE, PVC membrane material as research objects, mainly aiming at the creep theory of membrane material, creep experiment, the mechanical analysis of membrane structures and natural exposure research. The creep constitutive model and environmental influence factors of membrane material have been established. Then the dissertation do some research of membrane structural performance which is under the premise of material creep constitutive model, and put forward a definition of creep influence factors. At last, with the combination of environmental factors and creep factors, we discuss the mechanical property of membrane structure considering the effect of time-varying of membrane material, which can lay a foundation of the study of membrane material’s durability.The major research contents are listed as follows:1.Architectural membrane material creep constitutive model and creep experiment research.Based on creep mechanics, the viscoelasticity mechanics and theory of composite material, firstly, we discuss the creep properties and mechanism and make a introduction of three types of creep constitutive models. Then according to the results of creep experiment we determined the parameters of constitutive models and set up two kinds of creep constitutive models through the comparison and analysis, which can lay a foundation for subsequent research.2.The weatherability research of PTFE membrane material in cold regionThe dissertation has conducted a research on PTFE for 10 years in cold region, membrane samples which have been exposed in a natural environment for 1 year, 2 year, 4year and 7 year have been tested respectively, the tensile strength and tear strength of the samples have been tested year by year and regard them as the index for evaluating the weatherability of the PTFE. Based on test data, we make fitting curves to predict properties of membrane material, and provide a basis for membrane material’s selection.3.Research on mechanical performance of typical membrane structures considering the membrane material creep.Based on the creep experiment and creep constitutive models, the dissertation carry on mechanical analysis about two kinds of typical membrane structures with the help of ANSYS finite software, and make a discussion of the different factors which affect the performance of the structures. On this basis, the results of numerical simulation have been disposed in the way of statistical analysis. Then we define a factor that is influenced by creep behavior and find out the range of the factors. Finally, the applicability of the factors have been verified on other type of membrane structures.4.Based on the research of weatherability and creep performance, the strength safety factor of membrane structure during design and calculation are discussed in the dissertation.