Form‐finding Research Of Cable‐membrane Structures

The Cable‐Membrane Structure is a new‐type of spatial structure system, which has lots of merits such as light mass, the sheer ability of covering great span, high efficiency and novel modeling, it is becoming increasingly popular. The membrane structure can compose not only single‐curvature surface, but also the multi‐surface and other different type of structures, which can satisfy the unification of the architecture and aesthetics. Thus the Cable‐Membrane Structure buildings are widely adopted all over the world.The design of Cable‐membrane structure includes Shape design, the initial equilibrium shape analysis（form‐finding analysis which is also known as morphological analysis）, load analysis and cutting analysis. The correct cable‐membrane form of analysis is the foundation of the analysis and design phase, and is very important to the next step of load analysis and cutting analysis. Besides, it is also a prerequisite for the correct membrane structure design. It is directly related to the reasonable force, graceful shapement and price of the engineering system. There are some important parameters values of the cable‐membrane analysis and design (such as Cable and membrane Pre‐tension, Stiffness of the membrane tension, Cable‐membrane tension ratio etc.) which are positively correlated with the reasonableness and accuracy of form‐finding. Thus, how to control these parameters in reasonable values is the important part of the entire design process in the form‐finding.In the Construction of cable‐membrane structure instance, such as membrane surface folds, relaxation, tear etc. problems are often occurs. Therefore, how to avoid this kind of phenomenon which in the design process of form‐finding stage is significant.This paper describes the membrane material and the membrane structure characteristics and the main points of cable‐membrane structures design. Deduce and contrast the design theories (Nonlinear finite element method, force‐density method and dynamic relaxation method) of the membrane structure form‐finding for analysis, then obtain the advantages and disadvantages of three methods. Thus, in the cable‐membrane structure design process, we should use different theories combined with structural analysis of the characteristics, which has much more pertinence. Analyzed the Young’s modulus and improved measures of the form‐finding of tension membrane structures were presented combined with nonlinear finite element method, which obtained a more ideal result. The paper also adopt the software analysis of typical examples to get the parameters such as the Young’s modulus, cord and membranes, and the ratio of the initial pre‐tension, span ratio and the stiffness of tensioned membrane’s influence of the form‐finding results, which provides the contrast and advice or suggestions for the actual project. The paper find out the reasons of warping, relaxation and laceration, and the solutions are presented to avoid the problems like these in the actual engineering.