PSI - Issue 78

Riccardo Maurizio Ambrogio Baltrocchi et al. / Procedia Structural Integrity 78 (2026) 9–16

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were characterized by a strong coupling between horizontal and vertical ground motion components. In particular, the vertical acceleration recorded at different seismic monitoring stations reached notable intensities, with vertical peak ground accelerations (PGAv) measuring up to 1.0 g (Buratti et al., 2017; Di Sarno et al., 2011). This strong interaction effect between the seismic components also led to a large number of collapses by loss of support in those buildings with poor connections, highlighting the critical behaviour of precast elements under combined ground motions (Bovo & Savoia, 2018). However, vertical acceleration is generally neglected at the design level. Current design codes, such as the Eurocode and NTC 2018, suggest considering the vertical component of earthquake only for certain elements and for remarkably strong accelerations. In particular, Eurocode 8 (EN 1998-1, 2004), introduces the need to check beam members under the effect of vertical earthquake excitation only for areas of high seismic hazard (a vg > 0.25 g), which also covers near-fault areas, according to clause §4.3.3.5.2, when a member either spans 20 m or more, or it is prestressed, among other conditions, which makes practically all precast concrete horizontal members to be subjected to such check (Foti et al., 2023). The current typical design methods remain relatively simplistic, and this topic has received limited attention in the past literature. Among the main research employing sophisticated analytical approaches to investigate this phenomenon, the studies by Bovo & Savoia (2019) and Varevac et al. (2010) stand out. In particular, the first research applied OpenSees software to examine the non-linear dynamic behaviour of prestressed elements, comparing the analytical results with the predictions prescribed by Eurocode 8. Single and multi-bay RC precast buildings with strong connections and weak columns are studied. A database of 751 vertical acceleration records is considered, to conduct time-history analyses on 48 non-linear FE models. The use of Eurocode 8 response spectral analyses with a behaviour factor q = 1.5 underestimates the vertical force fluctuations induced by the earthquakes, suggesting a revision of the current design vertical spectrum. Manoukas & Tsiggelis (2024) investigated the seismic behaviour of a series of prestressed horizontal elements. In this study, SAP2000 is employed to conduct both linear and non-linear dynamic analyses, revealing the heightened vulnerability of upper-floor beams. Both modal response spectrum analysis method and dynamic analyses are considered to study beam performance. This research addresses the vulnerability of long-span precast roof elements under vertical seismic acceleration. Since the horizontal hinged members of industrial buildings are not directly part of the lateral load resisting system, the effect of the horizontal seismic component generally yields to negligible actions in the members, and thus this study only considers the decoupled vertical seismic acceleration component. To be noted that this assumption is not valid for the connections, which are however not the subject of the present investigation. The seismic performance of typical roofing elements of precast industrial building was analysed associated with three Engineering Demand Parameters (EDPs): first cracking, yielding, and failure, both in sagging and hogging conditions. Subsequently, the study undertakes a review of current design methodologies through direct comparison between linear and non-linear dynamic analyses, as well as examining the differences between coupled and uncoupled configurations of selected precast elements. 2.Method 2.1. Structure A series of uncoupled and coupled configurations were selected for this research, that are representative of long span precast structures (Dal Lago, 2017; Dal Lago et al., 2024), typical of industrial buildings. According to EC8 § 4.3.3.5.2, vertical seismic acceleration is considered for horizontal prestressed members spanning more than 20 m. For this reason, typical elements of industrial building roofing systems are chosen (Figure 1a,b).