Unreinforced masonry (URM) buildings are particularly prone to out-of-plane (OOP) failure mechanisms, typically governed by the vertical one-way bending of wall segments locally activated during seismic excitation. These mechanisms are commonly assessed using simplified rigid-body models and code-based kinematic procedures. This study evaluates the predictive accuracy and limitations of such codified approaches by comparing them against a more refined dynamic analysis framework. The code-based assessment is conducted through a nonlinear kinematic method, where seismic demand is defined through floor acceleration spectra specified in the Italian Building Code and the second generation of the Eurocode 8 prescriptions. In parallel, a time-history analysis procedure is developed, where a nonlinear single-degree-of-freedom (SDOF) model reproduces the global building response and generates floor accelerograms used to excite a second nonlinear SDOF model simulating the one-way bending of a vertical spanning strip wall (VSSW). A comprehensive parametric study is carried out, accounting for variations in wall geometry (height and thickness), vertical overburden load, and wall location along the building height. The two approaches are compared in terms of displacement demand and response consistency across the various wall configurations considered. Results are critically discussed within the context of seismic assessment practice, identifying conditions under which code-based procedures may deviate from the actual dynamic behaviour of OOP mechanisms.
Bertassi et al. (Thu,) studied this question.