Suspended Steel Roof of the Archeological Site of the School of Aristotle

Abstract

The structural design of the cable-suspended steel roof covering the archaeological site of the School of Aristotle in Athens, Greece is presented. The preliminary architectural proposal, which was awarded first prize in a competition organized by the Greek Ministry of Culture, provided for 65m span, arch-type main structures, each suspended by means of five suspension cables from a single pylon, stabilized by a pair of back-stay cables. Main arches were spaced at 11m and connected by means of purlins and bracing. The structural design concentrated on avoiding deviations from architectural requirements. Nevertheless, as a result of the vaulted shape of the roof, several cables were found to relax under service loads, thus the number, locations, cross-sections and prestressing of cables had to be re-evaluated. The present paper focuses on nonlinear analyses for understanding the behavior, predicting all possible failure mechanisms, and evaluating the ultimate strength of the roof by means of commercially available finite element software. Emphasis is placed on the role of flexural buckling of the pylon and lateral-torsional buckling of the main arch beam in the bearing capacity of these two members, both having complex geometry and varying cross-section, thus requiring a novel approach extending beyond code specifications. Failure dominated by either material yielding or instability is addressed, as well as interaction of failure modes. Steps include setting up an appropriate finite element model, obtaining critical buckling modes from linearized buckling analysis (LBA), and then using a linear combination of these modes as imperfection pattern for a geometrically and material nonlinear imperfection analysis (GMNIA). Equilibrium paths accompanied by snapshots of deformation and stress distribution at characteristic points are used to evaluate the analysis results, identify the dominant failure modes and optimize the structural performance.