Assessment of a Full-Scale Unreinforced Stone Masonry Building Tested on a Shaking Table by Inverse Engineering

Abstract

The material deterioration of an unreinforced stone masonry (URSM) building, due to subsequent dynamic loadings of increasing intensity on a shaking table, is investigated by means of inverse engineering, i.e. calibrating a finite element (FE) model to the experimental response data. The mechanical properties of the structure were initially estimated by preliminary characterisation tests. A two-storey full scale URSM building was tested on a shaking table using a sequential testing procedure of stationary and strong motion vibrations. The building was submitted to five uniaxial time-histories with gradually increasing intensity on a shaking table at the EUCENTRE laboratory (Pavia, Italy) up to a near collapse damage state, each one followed by a stationary vibration test. A frequency domain calibration was carried out to extract the mechanical properties of the equivalent elastic model. To this end, the stationary measurements were used to build up the state-space model. On the other hand, a recognition model was employed using the finite element method (FEM), whose stiffness and mass matrices were used to derive the corresponding analytical state-space model, which was compared to the experimental one. The calibration of the model against the experimental dynamic results includes increased complexity and high computational effort. Through an iterative optimisation trial and error procedure, the mechanical properties of masonry and the shear modulus of the flexible diaphragm of the structure for each test phase were derived. It is shown that the deterioration is more intense for the shear modulus of the walls compared to their elastic modulus. The ratio of the in-plane shear to the elastic modulus decreases substantially. The deterioration of the shear modulus of the timber floors is comparable with those of masonry walls.