Abstract Recent seismic events in Italy have emphasized the high vulnerability of masonry buildings in historical centers, which were generally erected in continuity to each other over time, resulting in aggregates of constructions. The study of the seismic behavior of masonry aggregates can turn into a very difficult task, usually because of the difficulties to achieve a complete knowledge of geometrical evolutions, state of the connections between structural units, and interventions carried out in the course of time. A wide number of local collapses has been observed after recent earthquakes in Italy, highlighting that collapse under horizontal loads may take place mainly through failure mechanisms of single portions of the aggregate. According to Italian Code, both global and local analyses can be adopted in the seismic assessment of single structural units. Therefore, the aim of this study is to investigate different approaches for the evaluation of the seismic vulnerability of historical masonry aggregates. A masonry aggregate located in the historical center of Arsita (Central Italy), which was hit by the 2009 L’Aquila earthquake, has been chosen as a representative case study and a wide set of local and global analyses has been carried out. Local analyses have been conducted through a new upper-bound limit analysis based on NURBS and mesh adaptation, and a kinematic limit analysis applied to the most common local mechanisms. Global analyses have been performed through pushover analyses using the Equivalent Frame Method, and pushover and nonlinear dynamic analyses on a detailed FE model with appropriate constitutive laws. Finally, a discussion about the effectiveness of the different analysis approaches is presented with reference to the results obtained in this study.

中文翻译：

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历史砖石骨料地震评估的高级数值策略

摘要 意大利最近发生的地震事件强调了历史中心的砖石建筑的高度脆弱性，这些建筑通常随着时间的推移相互连续竖立，导致建筑的聚集。砌体集料的抗震性能研究可能会变成一项非常艰巨的任务，通常是因为难以全面了解几何演化、结构单元之间的连接状态以及随时间进行的干预。在意大利最近发生的地震之后，观察到了大量的局部倒塌，这表明在水平载荷下倒塌可能主要是通过骨料单个部分的破坏机制发生的。根据意大利法典，在单个结构单元的抗震评估中可以采用全局和局部分析。因此，本研究的目的是研究评估历史砖石骨料地震脆弱性的不同方法。位于阿尔西塔（意大利中部）历史中心的砖石骨料被选为代表性案例研究，并进行了广泛的本地和全球分析，该地区遭受了 2009 年拉奎拉地震的袭击。局部分析已通过基于 NURBS 和网格自适应的新上限分析以及应用于最常见局部机制的运动学极限分析进行。使用等效框架法通过 Pushover 分析进行了全局分析，对具有适当本构律的详细有限元模型进行推覆和非线性动力学分析。最后，参考本研究中获得的结果，讨论了不同分析方法的有效性。