Theoretical Research Of Cable-Membrane Structures And Application On The Expo Axis Project In Shanghai

The Expo Axis project is the biggest landscape building and the major walking passage of the Expo Park of the Expo 2010 Shanghai. Its roofing system is composed of tensioned cable-membrane structure and free surface steel structures. As the biggest tensioned cable-membrane structure in the world, it is about 840m long,100m wide and covers about 64,000m2. The analysis of the Expo Axis roof is a great challenge for its large scale and complex shape. This paper makes some improvement on the theory of tensioned cable-membrane structures and applies it to the design of the Expo Axis project.Chapter 1 briefly summarizes the classifications of membrane structures and the development history of modern membrane structures in China. The theory status of tensioned cable-membrane structures is also studied systematically.In chapter2, the theory of force density method is reviewed and an improved nonlinear force density method taking into account the effect of 2-dimensional deformation of the membrane surface is presented. The improved method gains more accurate form finding result of tensioned cable-membrane structures. The area algorithm of the irregular space polygon is proposed to calculate the width of the membrane link. The form finding analysis of the Expo Axis project is done with the program of this method.Chapter3 presents a force density method based on multi-coordinate-system which deals with the form finding analysis of tensile structures with complex oblique boundaries and spring boundaries. The program of this method is written and four numerical examples are given to illustrate the efficiency of this method. In the form finding analysis of the Expo Axis project, this method is used to deal with the spring boundary of the Sun Valley steel structures and the oblique boundaries of sector model.In chapter4, some secondary development of EASY software is given. The secondary development contains three programs about the form finding analysis, wind load analysis and the post processing of the results. The topology refining program eliminates the repeated node number of EASY model, avoiding the model topology mess. The wind load application program generates the wind pressure contour area for EASY based on the measuring point data of the wind tunnel experiment and makes the application of the wind load fast and accurate. The interface program exports EASY result files to AutoCAD DXF files. It gives the internal force and stress contour plots, nodal displacement contour plots and envelope value contour plots.In chapter5, the basic theory of the Vector Form Intrinsic Finite Element Method (VFIFE) is summarized systematically. Examples are given to prove the efficiency of this method on the analysis of small deformed structures, large deformed structures and mechanisms. The space truss element of VFIFE is also studied and verified by the plane truss frame example.In chapter6, the tensioned truss element, cable element and T element of VFIFE is proposed and verified. The progressive collapse of the tensioned cable-membrane structure of the Expo Axis project is analyzed by the self-written VFIFE program. The coupled dynamic structural and mechanical behavior is tracked. It is figured out that the structure has good performance against progressive collapse and some conclusions of the internal force time-history are also given.The last chapter gives the summary and some future research topics.