DIFFERENT VERIFICATION LEVELS IN THE EVALUATION OF THE SEISMIC CAPACITY OF MASONRY STRUCTURES

A variety of computational procedures has been developed, over the years, for the evaluation of the seismic capacity of the architectural heritage. Due to the peculiarities of box-type masonry structures, indeed, this problem is not suitable for the application of procedures commonly in use for r.c. and steel structures, based on the linear analysis of a frame model. The experience acquired in Italy following the seismic events in the last forty years has led to the development and subsequent codification of three different kinds of approach to this problem; in relation also to the progress of the computational tools, the procedures are associated to different levels of complexity and accuracy in the results.
\nInitially, attention was focused on simple computational tools, suitable for manual application. Within that context, the basic approach to the evaluation of the global shear resistance for a building was formulated. This kind of approach, although approximate, allows for a global and fast estimation of the seismic safety. For this reason, it has been recently revised and codified in the Italian Guidelines for the reduction of the seismic risk of heritage buildings.
\nIn the following years, through the experience coming from new earthquakes, it was possible to identify typical, systematically recurring collapse mechanisms, involving limited portions of the building. On this basis, with reference to limit equilibrium conditions, the analysis of local collapse mechanisms was developed and, subsequently, formalized in the building code.
\nFinally, in parallel to the progress of computational tools, global analysis systems have been developed, based on frame equivalent models of masonry buildings, incorporating suitable schemes for masonry elements; such systems are normally used for static non linear analyses. This approach is recognized by the Guidelines as the most accurate evaluation of the building seismic capacity.
\nIt is of interest to apply the above procedures to the same case study, in order to compare the three different evaluations of the seismic safety, and to compare the kind of information they can provide. In this work, this has been done with reference to an ancient masonry structure in the city of Naples, for which a detailed survey had been performed.