Investigation On Wrinkling Of Membranes And Failure Of Cable System Of Tensioned Cable-membrane Structures

Wrinkling analysis of membranes and failure analysis of cable systems are two important aspects in load analysis of tensioned cable-membrane structures. By the former, correct load responses can be obtained after appearance of wrinkled elements. By the later, quantitative analysis of the importance of structure members can be achieved, weak structure parts can be identified, failure modes and reliability index can be obtained as well. This paper conducted the following researches and got some valuable conclusions.(1) Since the precise shape and cables'pretension forces of actual cable-membrane project are all unknown, this paper proposes a shape analysis method by which cable force-finding can be considered in appropriate moment through the process of shape-finding. A small cable-membrane structure and a large cable-membrane project are analyzed, it is found that stable shape and proper distribution of pretension forces can be obtained quickly and effectively by this method. It also makes the force-finding and shape-finding a unified process.(2) A method to analyze wrinkled membrane by using the local coordinate system transposition and equivalent stiffness analysis is proposed. The method avoids dealing with the complex problem of full rank matrix in principal stress axe, and provides a new way to process wrinkling analysis. The results of wrinkling analysis of a saddle-shaped cable-membrane structure and an umbrella-shaped cable-membrane structure show that, this method can deal with wrinkled membranes effectively, and can obtain the actual load responses of membranes after the emergence of wrinkles.(3) To solve the divergence, low accuracy problems in membrane wrinkling analysis, and be better applied in practical engineering projects, zero shear modulus plus equivalent stiffness analysis method is proposed. This method is an improvement to the method of local coordinate transposition and stiffness equivalence. The new method can make principal stresses directions coincide with local coordinates without transposing it. The computational efficiency and accuracy are improved significantly. Two large-scale membrane stadium structures are analyzed by this new method, it is found that the method can quickly deal with wrinkles of large membrane structure, and it solves the difficulties of wrinkling analysis application in practical engineering projects.(4) Through analyzing the failure of cables, an important analysis method by combining DARE and sensitivity methods is proposed. The new method, based on system stiffness changing theory, can obtain importance factors quantitatively. According to results of importance analyses, an importance-weaken concept of critical cables by cable-division method is proposed. The calculation results of Baoan stadium show that this method can decrease critical cables'importance factors by cable-division of key cables, it can also increase the safety protection and improve the collapse- resistance capacity of the structural system.(5) A main failure mode finding method using path reliability values is proposed. The method searches main failure members and finds main failure modes via the reliable value which is newly introduced in this paper. A large cable-membrane structure is analyzed by the new method, the results show that the failure arrays position and failure length path can be visually identified according to the reliable value, and the positions of main failure modes can be judged preliminarily. So it can simplify the complex process of reliability calculations.