"Seo" system

Design of the structure

The design of the structure is performed at LANIK design centre.

The software has been developed within as from a basic space frame design programme that has been completed with several segments to permit its specific use at LANIK and for the structures developed by means of the SEO system.

The programme can be subdivided into three main parts.

The first one is a programme for generating space grids, allowing to create various geometrical configurations from different systems of rectangular, cylindrical and polar coordinates. It permits to cut, move and assemble different parts and allows for symmetric splitting, etc. The same programme module permits to assign the profile properties (sections, etc.) in either a manual or a more or less automated way. Besides, it can generate the various load hypotheses and environmental conditions.

The second part of the programme constitues the central design system provided with a module for the study of dimensioned structures, that supplies, in terms of results, the fundamental displacements of each joint, the bar stresses and tensions, and the external reactions at the supports, both for simple hypotheses and for combinations of hypotheses which can be as many as desired. This analysis is performed through the stiffness matrix process. It starts from the assumption that the spherical joints are plain unions and it fixes three degrees of freedom for each joint. To define the equivalent stresses in compressed bars, the programme applies the coefficients as recommended by the EUROCODE 3: Design of Steel Structures. But this table can be modified to the taste of the designer, since it is not an intrinsic part of the programme.

This second part of the programme also includes, after each analysis, a re-sizing process meant to change the bars that could have been underdimensioned during the preliminary analysis. This process can be carried out either interactively or automatically, proceeding with the analysis of the redimensioned structure. In the automatic mode, re-sizing is made as many times as necessary to ensure that all the bars are subject to stresses lower than the admissible ones. Interactively, other profiles or bars of the structure could be altered if it were deemed useful for aesthetics or homogeneity's sake.

The third part of the programme consists in releasing the output data when the bar, bolt and joint dimensioning is completed. The programme compares all the data with respect to previous information and classify them according to identical ensembles, which results in the issue of the listings of bars and joints. To do so, a series of verifications like those required in order to detect the possible interferences between the bars fitted into the same spherical joint, etc. are performed and, if necessary, the situation is corrected. All these data, that represent the instructions for the factory, are both supplied in the form of listings and drawings and translated into a language readable by the Numerical Control of the machines used in the grid constituents manufacturing process, especially of the joint machining centre already referred to in a previous section. This part of the programme also prepares the space frame erection drawings.