A methodology for the seismic multilevel assessment of unreinforced masonry church inventories in the Groningen area

As a result of changes in seismicity in the Groningen area, a need has arisen to be able to rapidly assess and prioritize entire inventories of unreinforced masonry churches. As a part of being able to provide resource optimization to determine which structures are in most need of intervention, a multilevel methodology to assess seismic performance is presented. The process involves both data collection and vulnerability assessments. This multilevel approach involves progressive refinements to the data collected and to the complexity of the analyses conducted. Five data collection phases are used in conjunction with three progressively more complex methods for the seismic assessment. The first level of assessment uses only statistical information of the structures with information that can be obtained through desktop reviews. The second level of analysis uses key characteristics of wall thickness and height to develop simple models for each wall in each church. This level of analysis requires at least a preliminary site visit. In the third level of analysis, a more refined model of the church is developed from detailed site surveys of the structure where each wall is modelled and assessed. The process involves the assessment of the in-plane behaviour of either whole churches or single walls (global response) and the out-of-plane behaviour of single elements (local response). The study applies the approaches outlined in the NEN NPR9998 2017 combined with the Italian Standards for the cultural heritage. This paper outlines this Seismic Multilevel Assessment of Churches methodology and how it applies to an inventory of 52 unreinforced masonry churches in the Groningen area, The Netherlands.