Shape finding and structural analysis for cable type structures

Abstract

Nowadays, cable structures are gaining prominence in civil engineering against the traditional constructions thanks, among other reasons, to their lighter, to a better optimization of the material mechanic properties, the saving of material or its great beauty. Despite the great advances in recent decades in the creation of new processes, software and models for the design and analysis of cable type structures using in most cases the Finite Element Method, still remain major problems in these processes due to the flexibility of the cable elements and the need to settle the length of the cables and the possible large nodal displacements. This work deals with the main aims of the understanding those problems for the most important cable type structures shape finding and structural analysis, at the same time that the features of those structures, mainly the cable-stayed bridge and the suspension bridge, and their relation with the analysis using F.E.M. are understood and analyzed. All have been possible thanks to the realization of three examples, two proposed by Dr. Iwasaki and a model of an actual cable-stayed bridge using for all of them the Finite Element Method software, comp++. This program developed in the Department of Civil and Environmental Engineering of The Nagaoka University of Technology, provides the great advantage of have implemented a new concept of pulley that suppose a major advance in resolving the cable structures shape finding and structural analysis problems. After complete the exercises, can be done several reflections about the efficiency, accuracy and easily of F.E.M. in the execution of shape finding and structural analysis of cable type structures. And, what is more important and original, the importance of the new concept of pulleys from Dr. Iwasaki and Dr. Dang, crucial in controlling the length of the cables sliding through them, and in the settling of nodal coordinates. Making, thanks to the new developments, the shape finding much simpler and intuitive, through the possibility of impose restrictions and assumptions of displacements or pre-stresses in cable elements and pulleys. The main interest of this new developed system of pulleys is that, after one step of the shape finding, the results can be used to the next step, or them can bind into nodes and continue applying new loads with the structural analysis, which was not possible in this way before these important advances.