Modelling the nonlinear static response of a 2-storey URM benchmark case study: comparison among different modelling strategies using two- and three-dimensional elements

This paper aims at comparing the use of different software environments for the study of a simple unreinforced masonry building through nonlinear static analyses. The presented results are part of a wider research project conducted within the ReLUIS consortium, and specifically within a research task whose purpose is providing practitioners with results and tools for an aware employment of commercial software packages for modelling masonry structures. In this study one of the benchmark structures of the research program is analysed; a two-story building characterized by rigid horizontal diaphragms, considering different configurations in terms of openings arrangements and effectiveness of ring beams, is subjected to seismic load conditions. Software packages considering two- and three- dimensional structural models are employed, and the obtained results are compared in terms of capacity curves and collapse mechanisms. One of the critical aspects on the basic assumptions made by software in terms of way to apply the horizontal loads is further investigated. In addition, the role of the shear strength is analysed correlating the mechanical properties to be adopted with micro- and macro- models. The considered models present very different features, and the analogies and differences obtained in the results are critically interpreted in view of the different hypotheses made by the software tools in terms of modelling strategies and adopted constitutive laws.

Modelling the seismic response of a 2-storey URM benchmark case study: comparison among different equivalent frame models

The paper presents the comparison of the results of non-linear static analyses performed with different software based on the equivalent frame (EF) modelling approach on a simple two-story unreinforced masonry building with rigid diaphragms. This study is part of a wider research activity carried out in the framework of the Italian Network of Seismic Laboratories (ReLUIS) projects, funded by the Italian Department of Civil Protection. Different configurations have been considered varying the layout of the openings on the bearing walls and the structural details. The EF models have been defined adopting as much as possible common assumptions, in order to reduce the epistemic modelling uncertainties and to facilitate the interpretation of the differences in the results obtained by the software. The comparison involved different aspects: the global scale response, in terms of capacity curves, the predicted damage pattern as well as checks at the local scale, in terms of distribution of the generalized forces. Moreover, in order to assess the reliability of the obtained results, the numerical predictions have been compared to an analytical upper bound reference solution. Finally, the sensitivity of the numerical response to the criterion adopted for the EF idealization of masonry walls has been investigated.

Seismic performance of a retrofitted heritage unreinforced masonry building during the 2010/2011 Canterbury earthquakes

The Heritage Hotel (formerly Old Government Buildings) is one of the architectural heritage icons of Christchurch, New Zealand. Seismic retrofitting was undertaken on the structure in 1995 to achieve the earthquake loading provisions of the 1992 standard for design loadings (NZS 4203:1992). This building is a distinguished 1909 unreinforced masonry Italian High Renaissance palazzo building. The retrofit work included the installation of new lateral load-resisting structural systems, refurbishment of individual building elements, and partial building demolition with a total cost of approximately NZ$3.75 million. Detailed observations following the 2010/2011 Canterbury earthquakes showed that the building was subject to only minor damage during the September 2010 earthquake, whereas the February 2011 event caused some damage to exterior stonework and flooding in the basement due to liquefaction. This damage was easily repaired, and the building was fully functional by September 2013. Reported herein are details showcasing the success of the seismic retrofit and post-earthquake performance observations.