Ground motions and scaling techniques for 3D performance based seismic assessment of an industrial steel structure

This paper presents a performance-based earthquake assessment of an industrial structure, aiming at identifying suitable techniques to select and scale natural ground motions for 3D analysis and improve the structural response prediction of complex structures. To this end, an industrial structure characterized by the presence of large masses placed at a significant height and of different horizontal resisting systems, such as moment resisting frames, inverted V bracings and diagonal bracings, is investigated. The structural response is computed via both nonlinear static and dynamic analyses. Two sets of natural ground motions, one coherent with the Uniform Hazard Spectrum and one with the Conditional Mean Spectrum, are selected and scaled with different criteria. The efficiency and sufficiency of each selected ground motion set and scaling criteria is assessed through a probabilistic treatment of the key engineering demand parameters. Results indicate that for the structure analyzed, characterized by different behavior in the two orthogonal directions, the use of more complex ground motions selection and scaling techniques does not improve necessarily the reliability of results or allow the use of a lower number of ground motion recordings.