Incremental Dynamic and Nonlinear Static Analyses for Seismic Assessment of Medieval Masonry Towers

Discrete rigid blocks interacting through nonlinear elastic damageable interfaces are used to model the global behavior of a medieval masonry tower under seismic actions. The seismic vulnerability assessment is carried out by nonlinear static analysis (NSA) and incremental dynamic analysis (IDA), whose results are compared. It is confirmed that NSA results with both triangular and uniform load distributions are safety preserving and could be adopted for design scopes. In addition, the nondimensional horizontal-displacement threshold of 0.6% proposed by some building codes for existing masonry structures is aligned with NSA results and underestimates the capacity of the structure obtained by IDA. A comparison in terms of fragility curves highlights that NSA accounting for material uncertainties and IDA with record-to-record variability provide comparable levels of dispersion.