Fragility analysis of masonry arch with geometrical uncertainties under sine pulse base motion

In this paper, the dynamic response of circular masonry arch subjected to a sine pulse ground motion is analysed, taking into account geometrical uncertainties related to shape defects. In order to generate the irregular geometry of the arch, the main geometrical parameters, i.e.The radius, the angle of embrace of the voussoirs and the thickness, are considered as random variables with uniform probability density functions. The dynamic analysis is performed by referring to an equivalent SDOF system made of three blocks hinged at their ends, whose equation of motion is derived from Lagrange's equations. Incremental Dynamic Analyses are carried out considering the arch with nominal geometry or geometrical uncertainties. The results are showed by means of a fragility curve, which attempts to quantify to what extent geometrical uncertainties modify the failure of the arch under sine pulse base motion.