Abstract Summary
The conservation of reinforced concrete modern heritage structures requires careful consideration of multidisciplinary aspects. Among these, the structural safety evaluation plays a key role, and the assessment of the residual structural performances shall rely on a thorough knowledge of the current status of the structure [1]. A useful evaluation technique to achieve this makes use of the dynamic structural characterization, identification and monitoring of the structure that extract information on the actual structural behavior from the data acquired during vibration tests. Within this context, this study deals with the dynamic characterization of the Palazzetto dello Sport in Rome, one the most celebrated architecture by Pier Luigi Nervi [2]. Listed since 2021, the Palazzetto was conceived together with the architect Annibale Vitellozzi, and it was built in 1957 as part of the Nervi’s facilities built for the Olympic Games in 1960. The study is based on an experimental dynamic testing campaign recently carried out thanks to a research agreement with the Department for Sports and Youth Policies of Rome Municipality. The building is characterized by a reinforced concrete structure consisting of a shallow spherical dome with radius of 29.5 supported by 36 Y-shaped radially arranged trestles, inclined according to the tangent at the dome lower edge. Based on archive drawings and documents as well as a laser-scanner survey, an accurate initial 3D numerical model of the structure is developed. From the experimental data the modal identification is carried out through an Operational Modal Analysis (OMA) approach. The latter is tailored to cope with the peculiar dynamics of the dome, realised by Nervi as a ribbed spherical cap through a patented prefabrication process assuring the axial symmetry of the whole structure. In particular, high modal density is observed together with the dynamic features associated to the axial symmetry. Among them, the presence of non-axisymmetric modes with frequencies identical to the axisymmetric ones. In this case the degeneracy of the eigenfunctions corresponding to the spherical shell modes implies that the superposition of axisymmetric modes of identical frequency, but different orientations of axes, gives rise to new modes which are not necessarily symmetric with respect to any axes [3]. An ad-hoc FE model updating procedure including experimental modal frequencies and shapes is implemented. By resorting to pseudo-experimental response, the repeated modes analysis is performed by applying the space-MAC criterion validation. [1] Paolo Di Re, E. Lofrano, Jacopo Ciambella, and Francesco Romeo. Structural analysis and health monitoring of twentieth-century cultural heritage: the flaminio stadium in Rome. Smart Structures and Systems, 27:285–303, 02 2021. [2] Jae Hoon Kang. Vibrations of deep and shallow hemi-spheroidal domes with non-uniform thickness having a top cut-out. JVC/Journal Vib. Control, 22(11):2671–2686, 2016. [3] Erica Lenticchia, Rosario Ceravolo, and Cristiana Chiorino. Damage scenario-driven strategies for the seismic monitoring of XX century spatial structures with application to Pier Luigi Nervi’s Turin Exhibition Centre. Eng. Struct., 137:256–267, apr 2017.
