PROBABILISTIC SEISMIC VULNERABILITY ASSESSMENT OF FREESTANDING HISTORIC MONUMENTS

Seismic events can cause significant damage to structures, especially to freestanding structures which are not fixed to the ground and are free to rock independently. This thesis will study the response of freestanding statues and monuments to ground motions and develop probabilistic models for overturning, in order to assist in retrofitting and repair efforts. To do this, single and dual block system models were created with a variety of sizes, aspect ratios, and asymmetries, then subjected to several historic ground motions to determine whether they overturn using three-dimensional distinct element analysis as a result of rocking, sliding or twisting in three dimensions. Overturning results were then cast in a probabilistic formulation using logistic regression to generate seismic fragility curves which relate the probability of overturning to a measure of earthquake intensity. Sixty-three intensity measures were used to generate both scalar and vector fragility curves. The performance of each intensity measure was evaluated using Receiver Operator Characteristic analysis for all shapes and intensity measures. While the Cumulative Absolute Velocity, Response Spectrum Intensity, and Velocity Spectrum Intensity were the best performing scalar intensity measures, they did not consistently meet the requirements for an efficient IM across all models. Considering vector intensity measures yielded several vector IM pairs proved to be the most robust, however, they are not currently computable and therefore were not considered for this thesis’ recommendation. The combination of Cumulative Absolute Velocity and Peak Ground Acceleration as the most robust and computable intensity measure for all the models considered here. Advisor: Christine E. Wittic