High performance computing applied to the seismic finite element analysis of an historic structure: the Temple of Athena in Paestum

Historical masonry structures constitute an extremely varied and complex set as far as building techniques. The analyses of their structural behaviour, when excited by a seismic event, are often affected by considerable uncertainty arising from the hypothetical definition of the mechanical properties of materials and of the constraint conditions between the elements. The mechanical modelling of a historic building requires a knowledge of the properties of the various elements that make up the masonry and of the role they play: the masonry material, its use in the various components and, finally, how the connection between different elements are made in order to construct the building. The results of the work of modelling and the results of static and dynamic (seismic) analysis of the Temple of Athena, part of the broader site of monumental historical buildings in the Plain of Paestum, are presented in this paper. This work is part of the research project "Costruito", carried out within the Istituto di Cibernetica "E. Caianiello" in Naples, which has, among its objectives, the purpose to define the main phases of the procedure that, starting from the identification of a historical building, ends with the determination of its structural behaviour in static and seismic phases. The entire structure of the Temple of Athena has been modelled through a micro-modelling strategy in order to reproduce as faithfully as possible the whole geometry of the building. This approach has the disadvantage of being computationally expensive, given the large number of finite elements to be generated, but at the same time the merit of allowing, at a later stage, a more thorough validation and verification. To face the high computational cost, particular attention was paid to the continuous verification in the modelling phase, through an accurate test quality of the meshed finite elements. The control of the characteristic length of each element has allowed a lower limit to the size of time step to be established and to contain within certain limits the duration of simulations. With respect to this objective it has proved successful the choice of the modelling and pre-processing software, Hypermesh, that provides advanced features for the meshing procedure together with many effective testing tools. The solver adopted for the simulation phase is Radioss, whose characteristics are well fit for the modelling of the contacts between surfaces (penalty based methods for the contact). A parallel version of this software (four CPUs) was used for the simulation on a vector parallel machine NEC Sx-8. The results of simulation tests regarding static and seismic analysis are finally presented.