SCALE MODELS FOR THE EXPERIMENTAL ANALYSIS OF THE COLLAPSE MECHANISMS OF MASONRY BAY WINDOWS UNDER HORIZONTAL ACTIONS

The present contribution illustrates a first set of results obtained within the framework of currently on-going research aimed at evaluating the seismic vulnerability of masonry buildings in Boston’s Back Bay area. In particular, the study focuses on the collapse mechanisms of "bay windows", a typical late 19th century architectural element of the Victori- an style that characterizes the facades of Back Bay’s old buildings. With the aim of investigating the main features of bay windows response to horizontal loads, the analysis is focused on a single bay window considering it isolated from the rest of the building and resting on a rigid basement. A series of experimental tests has been conduct- ed on five scale-model bay windows of varying height free from openings. A system of hori- zontal actions proportional to the model mass density distribution has been imposed during the test by placing the model on a "tilting-table". The recordings of two digital video cameras allowed the identification of the collapse mechanisms. The results obtained are described in terms of determination of the horizontal loads col- lapse multiplier and identification of the actual collapse mechanisms. In addition, a first in- terpretation of the experimental results is provided by means of some simple mechanical schemes that use the typical tools of limit analysis. The agreement between experimental and theoretical results is more than satisfactory, and the proposed theoretical schemes seem able to provide useful information for assessing the mechanical response of bay windows.