2014 Theses Doctoral

Experimental Study of Rocking Motion of Rigid Bodies on Deformable Medium via Monocular Videogrammetry

Greenbaum, Raphael

The study of rigid body rocking is applicable to a wide variety of structural and non-structural elements. The current applications range from bridge pier and shallow footing design to hospital and industrial equipment, even art preservation. Despite the increasing number of theoretical and simulation studies of rocking motion, few experimental studies exist. Of those that have been published, most are focused on a constrained version of the complete problem introducing modifications to the physical problem with the purpose of eliminating either sliding, uplift or the three dimensional response of the body. However, all of these phenomena may affect the response of an unrestrained rocking body. Furthermore, the majority of the experimental studies that have been published have used methods that are ill-suited to comprehensive three dimensional experimental analysis of the problem.
The intent of this work is two-fold. First, to present a computer vision method that allows for the experimental measurement of the rigid body translation and rotation time histories in three dimensions. Experimental results obtained with this method will be presented to demonstrate that it obtains greater than 97% accuracy when compared against National Institute of Standards and Technology traceable displacement sensors. The experimental results highlight important phenomena predicted in some state-of-the-art models for 3D rocking behavior. Second, to present experimental evidence of the importance of characterizing the support medium as deformable instead of the commonly assumed rigid model. It will be shown in this work that this assumption of a rigid support may in some cases lead to non-conservative analysis that is unable to predict rocking motion and, in some cases, even failure.