Seismic performance of historic masonry buildings: A comparative analysis of equivalent frame and block-based methods

Many Italian historic buildings are located in earthquake-prone areas and, therefore, need effective seismic evaluations. Most widespread commercial codes are based on the Equivalent Frame Model (EFM). To investigate their reliability, particularly to assess the effect of tie-rod retrofitting interventions, the present research applies an EFM approach via 3Muri software to a detailed 3D digital model of Villa Vannucchi, a heritage building in southern Italy. The combined use of 3Muri for the 3D global behaviour and linear kinematic approaches for the 2D out-of-plane response shows the need for the installation of tie-rods. Looking at the 2D main facade, the effectiveness of 3Muri in capturing the beneficial effect of tie-rods is investigated against parametric analyses carried out with a standard limit analysis block-based method (BBM). Specifically, using the exact EFM's discretization and boundary conditions, the 3Muri results are benchmarked against the BBM adopting two modelling strategies: BBM pushover analysis with the same modelling strategy and loading conditions used by 3Muri, and BBM tilting tests. With the first strategy, it is shown that BBM provides results in good agreement with 3Muri; however, these results are independent of the tie-rod tension and presence because of inappropriate modelling of loading conditions. Conversely, the second strategy overcomes this drawback by better capturing the positive influence of the tie-rods both in terms of collapse mechanisms and an improved base shear capacity. The results of this research suggest that limit analysis represents a key, useful, and viable tool that needs to be integrated with EFM results in order to better capture the real effectiveness of tie-rod strengthening interventions, allowing for more sustainable consolidation strategies.