  A methodology for the performance-based seismic risk assessment of classical
columns is presented. Despite their apparent instability, classical columns
are, in general, earthquake resistant, as proven from the fact that many
classical monuments have survived many strong earthquakes over the centuries.
Nevertheless, the quantitative assessment of their reliability and the
understanding of their dynamic behavior are not easy, because of the
fundamental nonlinear character and the sensitivity of their response. In this
paper, a seismic risk assessment is performed for a multidrum column using
Monte Carlo simulation with synthetic ground motions. The ground motions
adopted contain a high- and low-frequency component, combining the stochastic
method, and a simple analytical pulse model to simulate the directivity pulse
contained in near source ground motions. The deterministic model for the
numerical analysis of the system is three-dimensional and is based on the
Discrete Element Method. Fragility curves are produced conditional on magnitude
and distance from the fault and also on scalar intensity measures for two
engineering demand parameters, one concerning the intensity of the response
during the ground shaking and the other the residual deformation of the column.
Three performance levels are assigned to each engineering demand parameter.
Fragility analysis demonstrated some of the salient features of these spinal
systems under near-fault seismic excitations, as for example, their decreased
vulnerability for very strong earthquakes of magnitude 7 or larger. The
analysis provides useful results regarding the seismic reliability of classical
monuments and decision making during restoration process.
