Vulnerability of precast concrete decks to vertical earthquakes

Past Italian earthquakes, such as the L’Aquila 2009 and Emilia 2012, were characterized by a strong combination of horizontal and vertical components of seismic acceleration, which highlighted the vulnerability of long-span precast structures. Nevertheless, common design practice neglects the effect of the vertical component, despite current codes prescribe specific checks for horizontal prestressed and long-span members in regions of high seismic hazard only. In such cases, simplified linear calculations based on simply supported uncoupled members are typically carried out. However, there is limited knowledge about the actual behaviour of such members under vertical acceleration. This study addresses the seismic performance of various configurations of a 25 m wing-shaped roof element supported by a I-shaped beam, representative of a typical long-span deck grid for modern precast industrial buildings. Linear and non-linear analyses were carried out considering both uncoupled and coupled roof decks, encompassing Linear Static Analysis (LSA), Natural Frequency Analysis (NFA), Spectral Response Analysis (SRA), and Non-linear Time-History Analysis (NLTHA). The comparison between different coupled and uncoupled configurations revealed critical insights into the realistic behaviour of long span precast elements under vertical seismic loading. The analysis of the data collected allowed also to critically assess the current design methodologies, and to highlight potential improvements.