A simple, design-oriented model of joints in vehicle structures is developed. This model accounts for the flexibility, the offsets of rotation centers of joint branches, and the coupling between rotations of a joint branch in different planes. The model parameters consist of torsional spring rates, the coordinates of the flexible hinges, and the orientations of planes in which the torsional springs are located. The model parameters are selected to be physically meaningful. In some cases, the behavior of joints can be accurately represented by using simpler models. The conditions under which the joint model can be simplified are discussed. A family of joint models with different levels of complexity are also defined. A probabilistic system identification is used to estimate the joint parameters by using the measured displacements. The parameters are estimated by minimizing the discrepancies between the measured and predicted displacements. Statistical tests which identify important parameters are also presented. These tests can be used to simplify the joint models without significantly reducing the accuracy in predicting structural responses. The identification methodology is applied to automotive structures with joints and also to isolated subassemblies consisting of joints and attached branches. / Ph. D.