Applicability of FEM and pushover analysis to simulate the shaking-table response of a masonry building model with timber diaphragms

Abstract

The seismic behaviour of unreinforced masonry (URM) structures is generally governed by a complex interaction between the out-of-plane and in-plane responses of the walls, depending on the in-plane stiffness of floor/roof diaphragms and the efficiency of wall-to-floor/roof connections. The presence of timber diaphragms, which are typically characterised by low in-plane stiffness and poor connection to the masonry walls, adds challenges to the numerical modelling and analysis, as well as to the structural assessment of URM structures under seismic actions. This work aims at investigating the applicability of refined FE modelling using macro-modelling approach and mass-proportional pushover analysis for simulating the response of URM structures with flexible diaphragms, comparing the results with experimental data obtained from incremental dynamic testing. A full-scale two-storey prototype building with timber diaphragms, which was tested in shaking table at the European Centre for Training and Research in Earthquake Engineering (EUCENTRE), in Italy, was considered to perform this study. A refined finite element (FE) model was developed in DIANA software, considering the wall-to-diaphragm (WTD) connections. While the strength values of masonry were adopted according to axial and diagonal compression tests, the modulus of elasticity was calibrated after simulating in-plane cyclic shear tests of masonry piers, which were part of the same experimental program at EUCENTRE. Recommendations from international guidelines were used to derive the assumed material properties for diaphragms and wall-to-diaphragm connections. Mass-proportional pushover analysis was performed and a comparison between numerical and experimental results is presented to investigate the assumptions, advantages and limitations of the presented numerical modelling and analysis approach.