Code-based ground motion selection and scaling for seismic assessment: Application to two masonry building case studies

This paper investigates the applicability and limitations of the guidelines for ground motion selection and scaling provided in the first- and second-generation of Eurocode 8 for the assessment of two unreinforced masonry buildings subjected to bi-directional loading. The numerical case studies consist of two unreinforced masonry buildings: one representative of stiff, monumental structures, and the other characterising tall, slender masonry typologies. Both structures are modelled in OpenSees using three-dimensional macroelements to capture the in-plane (IP) and out-of-plane (OOP) mechanisms, while also incorporating the effects of non-linear floor-to-wall connections and wall-to-wall interlocking. A total of ten sets of accelerograms are defined following the code-based requirements. These suites of accelerograms differ according to the version of Eurocode 8, seismological constraints, the range of matching, and the matching strategy, either uniform scaling or spectral matching. In addition to the bedrock case, soil classes B and C, defined according to Eurocode 8 prescriptions, are investigated. Subsequently, non-linear time history analyses are conducted for each building. The non-linear response obtained after the action of each set is thoroughly analysed in terms of mean and dispersion. Furthermore, the minimum number of records recommended in the code to characterise the mean seismic demand and its dispersion is examined. Finally, important remarks are drawn regarding ground motion selection and scaling guidelines, specifically oriented to the case of old masonry constructions.